NCERT - PHOTOSYNTHESIS IN HIGHER PLANTS - 24-25
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Questions and Answers

What is the photorespiration presence at low light intensities?

  • Always
  • Sometimes
  • High
  • Negligible (correct)

    • Temperature optimal for photosynthesis is usually above 40°C.

    False (B)

    Name one external factor that affects the rate of photosynthesis.

    Sunlight, temperature, CO2 concentration, or water

    The rate of photosynthesis is influenced by both internal and ______ factors.

    <p>external</p> Signup and view all the answers

    What is the probable photorespiration presence at high CO2 concentrations?

    <p>Negligible (B)</p> Signup and view all the answers

    The Law of Limiting Factors states that only one factor determines the rate of a process at any time.

    <p>True (A)</p> Signup and view all the answers

    Match the following factors affecting photosynthesis with their category:

    <p>Number of leaves = Internal Temperature = External Water availability = External Chlorophyll amount = Internal</p> Signup and view all the answers

    What kind of plant structure can be observed to study Kranz anatomy?

    <p>Vertical sections of leaves</p> Signup and view all the answers

    What did Joseph Priestley discover in 1774?

    <p>Oxygen (A)</p> Signup and view all the answers

    Priestley concluded that plants damage the air we breathe.

    <p>False (B)</p> Signup and view all the answers

    What essential role does sunlight play in the process of photosynthesis according to Ingenhousz's experiments?

    <p>Sunlight is essential for the process of photosynthesis.</p> Signup and view all the answers

    Joseph Priestley's experiment involved placing a ________ plant in a bell jar.

    <p>mint</p> Signup and view all the answers

    Match the scientist with their contribution to the understanding of photosynthesis:

    <p>Joseph Priestley = Discovered oxygen Jan Ingenhousz = Showed sunlight is essential for photosynthesis Burning candle = Consumes oxygen and releases carbon dioxide Aquatic plant = Produced bubbles with oxygen in sunlight</p> Signup and view all the answers

    What happens to a mouse in a closed bell jar without a plant?

    <p>It suffocates (B)</p> Signup and view all the answers

    Ingenhousz identified the bubbles produced by aquatic plants as carbon dioxide.

    <p>False (B)</p> Signup and view all the answers

    Jan Ingenhousz used an aquatic plant to demonstrate that plants release ________ in sunlight.

    <p>oxygen</p> Signup and view all the answers

    What is synthesized during electron flow in non-cyclic photophosphorylation?

    <p>Both ATP and NADPH + H+ (C)</p> Signup and view all the answers

    Cyclic photophosphorylation results in the synthesis of both ATP and NADPH + H+.

    <p>False (B)</p> Signup and view all the answers

    What is the location where cyclic photophosphorylation occurs?

    <p>Stroma lamellae</p> Signup and view all the answers

    Cyclic photophosphorylation occurs when only light of wavelengths beyond _____ nm are available for excitation.

    <p>680</p> Signup and view all the answers

    Match the following components with their functions:

    <p>PS I = Synthesis of ATP through cyclic flow PS II = Absorption of light energy NADP reductase = Reduction of NADP+ Thylakoid membrane = Location of proton gradient generation</p> Signup and view all the answers

    Which of the following statements is true about the electron transport chain in photosynthesis?

    <p>It connects both PS I and PS II. (D)</p> Signup and view all the answers

    Proton accumulation in photosynthesis occurs in the intermembrane space of thylakoids.

    <p>False (B)</p> Signup and view all the answers

    What hypothesis explains the ATP synthesis mechanism in chloroplasts?

    <p>Chemiosmotic hypothesis</p> Signup and view all the answers

    What did Julius von Sachs demonstrate about glucose?

    <p>Glucose is produced when plants grow. (D)</p> Signup and view all the answers

    Chlorophyll is located in the nucleus of plant cells.

    <p>False (B)</p> Signup and view all the answers

    What is the main light-dependent reaction in photosynthesis demonstrated by Cornelius van Niel?

    <p>Hydrogen from a suitable oxidizable compound reduces carbon dioxide to carbohydrates.</p> Signup and view all the answers

    In the equation for photosynthesis, the abbreviation [CH2O] represents a ________.

    <p>carbohydrate</p> Signup and view all the answers

    According to the key features of plant photosynthesis, plants use light energy to convert which of the following into carbohydrates?

    <p>Carbon dioxide and water (D)</p> Signup and view all the answers

    Match the following scientists with their contributions to photosynthesis:

    <p>Julius von Sachs = Production of glucose during plant growth T.W. Engelmann = Discovered the first action spectrum of photosynthesis Cornelius van Niel = Demonstrated light-dependent reactions and hydrogen donors Chlorophyll = Green pigment in plants responsible for photosynthesis</p> Signup and view all the answers

    Oxygen released by green plants during photosynthesis comes from carbon dioxide.

    <p>False (B)</p> Signup and view all the answers

    What type of organisms do not release oxygen during photosynthesis?

    <p>Purple and green sulfur bacteria</p> Signup and view all the answers

    Which of the following compounds is produced during the carbon fixation cycle by the enzyme RuBisCO?

    <p>3-phosphoglycerate (PGA) (A)</p> Signup and view all the answers

    The main product of the Calvin cycle is RuBP.

    <p>False (B)</p> Signup and view all the answers

    What is the wasteful reaction that RuBisCO can catalyze in C3 plants called?

    <p>Photorespiration</p> Signup and view all the answers

    The first product of CO2 fixation in C4 plants is a _____-carbon compound.

    <p>4</p> Signup and view all the answers

    In which part of the plant does the Calvin pathway occur in C4 plants?

    <p>Bundle sheath cells (D)</p> Signup and view all the answers

    Match the types of photosynthesis with their characteristics:

    <p>C3 Pathway = Uses CO2 directly in the Calvin cycle C4 Pathway = Initial product is a 4-carbon molecule Non-Cyclic Photophosphorylation = Produces ATP and NADPH Cyclic Photophosphorylation = Produces only ATP</p> Signup and view all the answers

    Chlorophyll b is essential for photosynthesis on its own.

    <p>False (B)</p> Signup and view all the answers

    Why are leaves on the sunny side of a plant typically darker green compared to those on the shady side?

    <p>They contain more chlorophyll to capture more light for photosynthesis.</p> Signup and view all the answers

    Which enzyme is responsible for the fixation of CO2 in C4 plants?

    <p>PEP carboxylase (B)</p> Signup and view all the answers

    C3 plants perform the Calvin pathway only in the bundle sheath cells.

    <p>False (B)</p> Signup and view all the answers

    What is the primary role of RuBisCO in the Calvin pathway?

    <p>CO2 fixation</p> Signup and view all the answers

    In C4 plants, the C4 acid formed is initially _____ in the mesophyll cells.

    <p>OAA</p> Signup and view all the answers

    Match the following compounds with their respective characteristics:

    <p>RuBisCO = Most abundant enzyme in the world 3PGA = Product of RuBP and CO2 reaction Phosphoglycolate = 2-carbon compound in photorespiration OAA = Initial C4 acid in the mesophyll</p> Signup and view all the answers

    What happens to the C4 acids in the bundle sheath cells?

    <p>They release CO2 and generate a 3-carbon molecule. (D)</p> Signup and view all the answers

    What is photorespiration, and why is it significant for C3 plants?

    <p>Photorespiration is a process where RuBisCO binds to O2 instead of CO2, leading to decreased efficiency in CO2 fixation. It is significant because it reduces the overall productivity of C3 plants.</p> Signup and view all the answers

    C4 plants lack RuBisCO in their mesophyll cells.

    <p>True (A)</p> Signup and view all the answers

    What molecule forms the reaction centre in both photosystems?

    <p>Chlorophyll a (C)</p> Signup and view all the answers

    Photosystem I has a reaction centre with an absorption peak at 680 nm.

    <p>False (B)</p> Signup and view all the answers

    What is the absorption peak of chlorophyll a in photosystem II?

    <p>680 nm</p> Signup and view all the answers

    What major research did Melvin Calvin contribute to in 1961?

    <p>Pathway of carbon assimilation in photosynthesis (C)</p> Signup and view all the answers

    All organisms, including humans, are autotrophs.

    <p>False (B)</p> Signup and view all the answers

    The process that moves electrons downhill through an electron transport system is called ______.

    <p>oxidation-reduction</p> Signup and view all the answers

    What is the process called that allows green plants to synthesize food using light energy?

    <p>photosynthesis</p> Signup and view all the answers

    Match the following chlorophyll absorption peaks with their photosystem:

    <p>Photosystem I = P700 Photosystem II = P680</p> Signup and view all the answers

    The green plants can be classified as ______ because they synthesize their own food.

    <p>autotrophs</p> Signup and view all the answers

    What is the primary role of the light-harvesting complex (LHC) in photosystems?

    <p>To absorb different wavelengths of light (D)</p> Signup and view all the answers

    In photosystem II, electrons are excited by green light.

    <p>False (B)</p> Signup and view all the answers

    Which of the following statements about autotrophs is true?

    <p>They convert sunlight into chemical energy. (B)</p> Signup and view all the answers

    What is the final acceptor molecule for electrons in photosystem I?

    <p>NADP+</p> Signup and view all the answers

    Plants synthesize food directly from sunlight without any other raw materials.

    <p>False (B)</p> Signup and view all the answers

    What substance did Melvin Calvin use to label carbon dioxide during his studies?

    <p>C14</p> Signup and view all the answers

    What is the primary product of photosynthesis?

    <p>Glucose (D)</p> Signup and view all the answers

    Photosynthesis only occurs in the green leaves of plants.

    <p>False (B)</p> Signup and view all the answers

    What are the two types of reactions involved in photosynthesis?

    <p>Light reactions and dark reactions</p> Signup and view all the answers

    In photosynthesis, the process of converting light energy into chemical energy occurs in the ______.

    <p>chloroplasts</p> Signup and view all the answers

    Match the components of chloroplasts with their functions:

    <p>Grana = Trap light energy Stroma = Synthesize sugar Stroma lamellae = Connect grana Matrix stroma = Enzymatic reactions</p> Signup and view all the answers

    Why is water (H2O) a crucial substrate in photosynthesis?

    <p>It releases oxygen during the process. (C)</p> Signup and view all the answers

    Even though dark reactions are called so, they can still occur in the presence of light.

    <p>True (A)</p> Signup and view all the answers

    Which of the following is NOT a requirement for photosynthesis?

    <p>Oxygen (D)</p> Signup and view all the answers

    What alignment do chloroplasts take when they require maximum light exposure?

    <p>Flat surfaces parallel to the walls of mesophyll cells</p> Signup and view all the answers

    Plants release oxygen during the process of photosynthesis.

    <p>True (A)</p> Signup and view all the answers

    What is the initial product formed from CO2 fixation in C4 plants?

    <p>OAA (D)</p> Signup and view all the answers

    What substance was used in one of the experiments to absorb CO2?

    <p>KOH (Potassium Hydroxide)</p> Signup and view all the answers

    C3 plants perform the Calvin pathway only in the mesophyll cells.

    <p>False (B)</p> Signup and view all the answers

    Photosynthesis converts light energy into ________ energy.

    <p>chemical</p> Signup and view all the answers

    What role does RuBisCO play in the Calvin pathway?

    <p>It catalyzes the reaction where RuBP combines with CO2.</p> Signup and view all the answers

    In the bundle sheath cells, C4 acids are broken down to release CO2 and a _____-carbon molecule.

    <p>3</p> Signup and view all the answers

    Match the following components involved in photosynthesis with their roles:

    <p>Chlorophyll = Absorbs light Light = Provides energy CO2 = Source of carbon Starch = Energy storage</p> Signup and view all the answers

    What was observed in the part of the leaf that was exposed to light during the starch test?

    <p>Tested positive for starch (B)</p> Signup and view all the answers

    Photosynthesis occurs only in the green parts of the plant.

    <p>True (A)</p> Signup and view all the answers

    What is the main purpose of photosynthesis in plants?

    <p>To produce food and oxygen</p> Signup and view all the answers

    Photorespiration occurs when RuBisCO binds to CO2 more efficiently than O2.

    <p>False (B)</p> Signup and view all the answers

    In what type of plant cells does the Calvin pathway occur in C4 plants?

    <p>Bundle sheath cells</p> Signup and view all the answers

    What is the primary role of RuBisCO in the carbon fixation cycle?

    <p>To catalyze the addition of CO2 to RuBP (A)</p> Signup and view all the answers

    C4 plants perform the Calvin cycle only in the mesophyll cells.

    <p>False (B)</p> Signup and view all the answers

    What are the products released during the splitting of water molecules in photosynthesis?

    <p>O2, protons, and electrons</p> Signup and view all the answers

    C4 plants initially fix CO2 into a _____-carbon compound.

    <p>4</p> Signup and view all the answers

    Match the following plant pathways with their characteristics:

    <p>C3 Pathway = Involves RuBisCO mainly in mesophyll C4 Pathway = Involves CO2 fixation in mesophyll and bundle sheath Calvin Cycle = Converts PGA to sugar Photorespiration = Wasteful reaction catalyzed by RuBisCO</p> Signup and view all the answers

    Which of the following correctly describes the function of ATP in the Calvin cycle?

    <p>ATP provides energy for the conversion of PGA to sugar (D)</p> Signup and view all the answers

    C4 plants are less productive than C3 plants due to more inefficient CO2 fixation.

    <p>False (B)</p> Signup and view all the answers

    Why do tropical plants exhibit the C4 photosynthesis pathway?

    <p>To increase efficiency in CO2 fixation and minimize photorespiration under high light and temperature conditions.</p> Signup and view all the answers

    What is the major limiting factor for photosynthesis in terms of gas concentration?

    <p>Carbon dioxide (A)</p> Signup and view all the answers

    C4 plants show saturation at a lower CO2 concentration than C3 plants.

    <p>True (A)</p> Signup and view all the answers

    What happens to the rate of photosynthesis when light intensity exceeds a certain limit?

    <p>It causes the breakdown of chlorophyll and a decrease in photosynthesis.</p> Signup and view all the answers

    Photosynthesis requires light, carbon dioxide, and ________.

    <p>water</p> Signup and view all the answers

    Match the following factors to their effects on photosynthesis:

    <p>High light intensity = Breakdown of chlorophyll Optimal temperature = Increased photosynthesis Low CO2 concentration = Limited CO2 fixation High CO2 concentration = Potential damage over time</p> Signup and view all the answers

    At what percentage of full sunlight does light saturation occur for most plants?

    <p>10% (A)</p> Signup and view all the answers

    Both C3 and C4 plants respond to high CO2 concentrations at low light conditions.

    <p>False (B)</p> Signup and view all the answers

    What is the relationship between incident light and CO2 fixation rates at low light intensities?

    <p>There is a linear relationship.</p> Signup and view all the answers

    What is the primary biological function of photorespiration?

    <p>Release of CO2 and utilization of ATP (C)</p> Signup and view all the answers

    C4 plants undergo photorespiration.

    <p>False (B)</p> Signup and view all the answers

    In which cells does the Calvin cycle occur in C4 plants?

    <p>Bundle sheath cells</p> Signup and view all the answers

    The primary CO2 acceptor in plants is __________.

    <p>RuBP</p> Signup and view all the answers

    Which of the following characteristics is true for C4 plants?

    <p>Photorespiration does not occur (B)</p> Signup and view all the answers

    Match the characteristics with either C3 or C4 plants:

    <p>Primary CO2 fixation product = PGA Cell type for initial carboxylation = Mesophyll Number of cell types involved in CO2 fixation = Two: Bundle sheath and mesophyll Presence of PEP Case = No</p> Signup and view all the answers

    Photorespiration is considered a beneficial process for plant productivity.

    <p>False (B)</p> Signup and view all the answers

    Name one reason why productivity is better in C4 plants compared to C3 plants.

    <p>Higher tolerance to temperature</p> Signup and view all the answers

    Which pigment is the most abundant in plants and plays a primary role in photosynthesis?

    <p>Chlorophyll a (B)</p> Signup and view all the answers

    Chlorophyll b is responsible for the maximum absorption of light in the red region of the spectrum.

    <p>False (B)</p> Signup and view all the answers

    How many different pigments are involved in photosynthesis according to the information provided?

    <p>Four</p> Signup and view all the answers

    Chlorophyll a shows maximum absorption in the ________ and ________ regions of the wavelength spectrum.

    <p>blue, red</p> Signup and view all the answers

    Match the following pigments with their corresponding color:

    <p>Chlorophyll a = Blue-green Chlorophyll b = Yellow-green Xanthophylls = Yellow Carotenoids = Yellow to orange</p> Signup and view all the answers

    Which process can be used to separate leaf pigments for analysis?

    <p>Chromatography (C)</p> Signup and view all the answers

    All pigments involved in photosynthesis absorb light at the same wavelengths.

    <p>False (B)</p> Signup and view all the answers

    What is the role of pigments in photosynthesis?

    <p>To absorb light</p> Signup and view all the answers

    Which organic acid is the first stable product of CO2 fixation in C4 plants?

    <p>Oxaloacetic acid (B)</p> Signup and view all the answers

    All plants have PGA as the first product of CO2 fixation.

    <p>False (B)</p> Signup and view all the answers

    What is the enzyme responsible for the carboxylation of ribulose bisphosphate (RuBP)?

    <p>RuBP carboxylase</p> Signup and view all the answers

    The primary acceptor of CO2 in the Calvin cycle is ________ bisphosphate.

    <p>ribulose</p> Signup and view all the answers

    Which stage of the Calvin cycle involves the fixation of CO2 into an organic intermediate?

    <p>Carboxylation (B)</p> Signup and view all the answers

    Match the following components of the Calvin cycle with their description:

    <p>Carboxylation = Fixation of CO2 into an organic intermediate Reduction = Conversion of 3-PGA into G3P Regeneration = Reformation of RuBP RuBP = 5-carbon sugar that accepts CO2</p> Signup and view all the answers

    The Calvin cycle occurs exclusively in plants using the C3 pathway.

    <p>False (B)</p> Signup and view all the answers

    How many carbon atoms does ribulose bisphosphate (RuBP) contain?

    <p>5</p> Signup and view all the answers

    Which of the following stages occurs first in the Calvin cycle?

    <p>Carboxylation (C)</p> Signup and view all the answers

    The Calvin cycle requires 2 ATP molecules for each CO2 fixed to produce glucose.

    <p>False (B)</p> Signup and view all the answers

    What is the primary enzyme involved in the fixation of CO2 during the Calvin cycle?

    <p>RuBisCO</p> Signup and view all the answers

    The final product generated in the reduction phase of the Calvin cycle is __________.

    <p>triose phosphate</p> Signup and view all the answers

    Match the following stages of the Calvin cycle with their respective descriptions:

    <p>Carboxylation = CO2 combines with ribulose-1,5-bisphosphate Reduction = Formation of glucose through NADPH and ATP Regeneration = Formation of ribulose-1,5-bisphosphate</p> Signup and view all the answers

    How many turns of the Calvin cycle are required to produce one molecule of glucose?

    <p>6 turns (A)</p> Signup and view all the answers

    The process of regeneration in the Calvin cycle requires ATP.

    <p>True (A)</p> Signup and view all the answers

    What two molecules are primarily used during the reduction phase of the Calvin cycle?

    <p>ATP and NADPH</p> Signup and view all the answers

    What compound is initially formed in the mesophyll cells of C4 plants?

    <p>OAA (C)</p> Signup and view all the answers

    The Calvin pathway occurs in the mesophyll cells of C4 plants.

    <p>False (B)</p> Signup and view all the answers

    What is the role of RuBisCO in the Calvin pathway?

    <p>It catalyzes the fixation of CO2.</p> Signup and view all the answers

    In photorespiration, RuBP binds with _____ instead of CO2.

    <p>O2</p> Signup and view all the answers

    Match the following plant structures to their functions:

    <p>Mesophyll Cells = Site of C4 acid formation Bundle Sheath Cells = Site of Calvin pathway PEP Carboxylase = Fixation of CO2 in C4 plants RuBisCO = Fixation of CO2 in Calvin pathway</p> Signup and view all the answers

    Which of the following enzymes is absent in the mesophyll cells of C4 plants?

    <p>RuBisCO (C)</p> Signup and view all the answers

    In C4 plants, CO2 is initially fixed to form a 4-carbon compound.

    <p>True (A)</p> Signup and view all the answers

    What is the end product of C4 acid breakdown in the bundle sheath cells?

    <p>CO2 and a 3-carbon molecule</p> Signup and view all the answers

    What does cyclic photophosphorylation primarily produce?

    <p>ATP (A)</p> Signup and view all the answers

    Cyclic photophosphorylation occurs when only light of wavelengths below 680 nm are available for excitation.

    <p>False (B)</p> Signup and view all the answers

    What is the main difference in proton accumulation during ATP synthesis in photosynthesis compared to respiration?

    <p>In photosynthesis, protons accumulate inside the thylakoid membrane lumen, while in respiration they accumulate in the intermembrane space.</p> Signup and view all the answers

    The electron transport chain connects the two ________ in the photosynthesis process.

    <p>photosystems</p> Signup and view all the answers

    Match the terms related to photosynthesis with their descriptions:

    <p>ATP = Energy currency of the cell NADPH + H+ = Reducing agent in biosynthetic reactions PS I = Photosystem that absorbs light at 700 nm PS II = Photosystem that absorbs light at 680 nm</p> Signup and view all the answers

    In cyclic photophosphorylation, where does the excited electron ultimately return?

    <p>To the PS I complex (D)</p> Signup and view all the answers

    The chemiosmotic hypothesis explains how ATP is synthesized in the chloroplast.

    <p>True (A)</p> Signup and view all the answers

    What is a likely location for cyclic photophosphorylation to occur in the chloroplast?

    <p>Stroma lamellae membranes</p> Signup and view all the answers

    What is the main consequence of the proton gradient created across the thylakoid membrane?

    <p>It leads to the synthesis of ATP. (B)</p> Signup and view all the answers

    The accumulation of protons in the lumen of the thylakoids increases the pH of the lumen.

    <p>False (B)</p> Signup and view all the answers

    Where does the NADP reductase enzyme operate in relation to the thylakoid membrane?

    <p>On the stroma side of the membrane</p> Signup and view all the answers

    The process of synthesizing ATP through the breakdown of the proton gradient is called __________.

    <p>chemiosmosis</p> Signup and view all the answers

    Match the following components of the ATP synthase enzyme with their functions:

    <p>CF0 = Forms a transmembrane channel for protons CF1 = Synthesizes ATP Proton gradient = Drives ATP synthesis Thylakoid membrane = Site of proton accumulation</p> Signup and view all the answers

    How do electrons contribute to the formation of a proton gradient?

    <p>By facilitating the transport of protons across the membrane. (B)</p> Signup and view all the answers

    The splitting of water molecules generates protons, which accumulate in the stroma.

    <p>False (B)</p> Signup and view all the answers

    What happens to protons during the transport of electrons in photosystems?

    <p>Protons are removed from the stroma and released into the lumen.</p> Signup and view all the answers

    What is the first product formed when CO2 is fixed in the Calvin cycle?

    <p>3-phosphoglyceric acid (PGA) (A)</p> Signup and view all the answers

    The biosynthetic phase of photosynthesis is directly dependent on the presence of light.

    <p>False (B)</p> Signup and view all the answers

    How many carbon atoms are in 3-phosphoglyceric acid (PGA)?

    <p>3</p> Signup and view all the answers

    Chemiosmosis is dependent on a membrane, a proton pump, a proton gradient, and ______.

    <p>ATP synthase</p> Signup and view all the answers

    Match the following products of photosynthesis with their uses:

    <p>ATP = Used for energy in biosynthetic reactions NADPH = Provides reducing power for biosynthetic reactions O2 = Diffuses out of the chloroplast</p> Signup and view all the answers

    What causes the conformational change in the CF1 particle of the ATP synthase?

    <p>Proton gradient (A)</p> Signup and view all the answers

    ATP can be utilized immediately in the biosynthetic reactions in the stroma after it is produced.

    <p>True (A)</p> Signup and view all the answers

    What discovery is Melvin Calvin known for in relation to photosynthesis?

    <p>He discovered the Calvin cycle and the initial fixation product of CO2, which is 3-phosphoglyceric acid (PGA).</p> Signup and view all the answers

    Which stage of the Calvin cycle involves the fixation of CO2 with ribulose-1,5-bisphosphate?

    <p>Carboxylation (B)</p> Signup and view all the answers

    The Calvin cycle requires 3 molecules of ATP and 2 of NADPH for every molecule of CO2 fixed.

    <p>True (A)</p> Signup and view all the answers

    What molecule is regenerated at the end of the Calvin cycle to allow the cycle to continue?

    <p>ribulose-1,5-bisphosphate (RuBP)</p> Signup and view all the answers

    The Calvin cycle consists of three main stages: carboxylation, reduction, and ________.

    <p>regeneration</p> Signup and view all the answers

    Match the stage of the Calvin cycle with its corresponding description:

    <p>Carboxylation = CO2 combines with ribulose-1,5-bisphosphate Reduction = Formation of carbohydrates utilizing ATP and NADPH Regeneration = Replenishment of ribulose-1,5-bisphosphate</p> Signup and view all the answers

    What are the products formed from the reduction stage of the Calvin cycle?

    <p>trioses (such as glyceraldehyde-3-phosphate)</p> Signup and view all the answers

    For every CO2 molecule fixed, the Calvin cycle requires 2 molecules of ATP but no NADPH.

    <p>False (B)</p> Signup and view all the answers

    How many ATP molecules are required to synthesize one molecule of glucose through the Calvin pathway?

    <p>18 (D)</p> Signup and view all the answers

    C4 plants typically have a process called photorespiration that is more active than in C3 plants.

    <p>False (B)</p> Signup and view all the answers

    What is the first CO2 fixation product in C4 plants?

    <p>Oxaloacetic acid</p> Signup and view all the answers

    The cells surrounding the vascular bundles in C4 plants are known as ______ cells.

    <p>bundle sheath</p> Signup and view all the answers

    Match the following components with their descriptions:

    <p>Kranz anatomy = Arrangement of bundle sheath cells around vascular bundles NADPH = Reducing agent in the Calvin cycle PEP = Primary CO2 acceptor in C4 plants Calvin cycle = Main biosynthetic pathway for glucose synthesis</p> Signup and view all the answers

    Which process do C4 plants primarily utilize for glucose synthesis?

    <p>Calvin cycle (A)</p> Signup and view all the answers

    How many NADPH molecules are required to make one molecule of glucose through the Calvin pathway?

    <p>12</p> Signup and view all the answers

    C4 plants have greater productivity of biomass compared to C3 plants.

    <p>True (A)</p> Signup and view all the answers

    Which pigments are classified as accessory pigments in photosynthesis?

    <p>Xanthophylls and carotenoids (B)</p> Signup and view all the answers

    The light reactions of photosynthesis do not involve the formation of ATP.

    <p>False (B)</p> Signup and view all the answers

    What are the two discrete light harvesting complexes involved in photosynthesis?

    <p>Photosystem I and Photosystem II</p> Signup and view all the answers

    Chlorophyll absorbs mostly light in the ___ and ___ regions of the spectrum.

    <p>blue, red</p> Signup and view all the answers

    What is the primary function of accessory pigments in photosynthesis?

    <p>To dissipate excess light energy (A)</p> Signup and view all the answers

    The main role of chlorophyll b is to act alone in photosynthesis.

    <p>False (B)</p> Signup and view all the answers

    What are the high-energy chemical intermediates formed during light reactions?

    <p>ATP and NADPH</p> Signup and view all the answers

    What does the Z scheme describe in photosynthesis?

    <p>The transfer of electrons through the electron transport chain (C)</p> Signup and view all the answers

    What is the primary product of photosynthesis represented in the equation?

    <p>Glucose (B)</p> Signup and view all the answers

    The splitting of water occurs associated with photosystem I.

    <p>False (B)</p> Signup and view all the answers

    Photosynthesis occurs only in the green leaves of plants.

    <p>False (B)</p> Signup and view all the answers

    What are the net products of water splitting in photosynthesis?

    <p>4H+, O2, 4e−</p> Signup and view all the answers

    During non-cyclic photo-phosphorylation, ATP is synthesized from ADP and inorganic ________ in the presence of light.

    <p>phosphate</p> Signup and view all the answers

    The oxygen released during photosynthesis comes from the breakdown of __________.

    <p>water</p> Signup and view all the answers

    Match the following components of photosynthesis with their functions:

    <p>PS II = Electron donor during water splitting NADP+ = Final electron acceptor PS I = Excitation of electrons ATP = Energy carrier</p> Signup and view all the answers

    What is one of the main outputs of the cyclic photo-phosphorylation process?

    <p>ATP (D)</p> Signup and view all the answers

    Match the following components of chloroplasts with their functions:

    <p>Grana = Site for light-dependent reactions Stroma = Site for sugar synthesis Thylakoid membranes = Site for ATP synthesis Chlorophyll = Pigment that captures light energy</p> Signup and view all the answers

    In cyclic photo-phosphorylation, only photosystem II is involved.

    <p>False (B)</p> Signup and view all the answers

    Why are chloroplasts usually aligned parallel to the cell walls in mesophyll cells?

    <p>To maximize light capture (D)</p> Signup and view all the answers

    Which complex is associated with photosystem II for supplying electrons?

    <p>water splitting complex</p> Signup and view all the answers

    The light reactions of photosynthesis do not require light.

    <p>False (B)</p> Signup and view all the answers

    What are the two products of the light reactions that are essential for the dark reactions?

    <p>ATP and NADPH</p> Signup and view all the answers

    How many molecules of ATP are required to produce one glucose molecule through the Calvin pathway?

    <p>18 (A)</p> Signup and view all the answers

    C4 plants show a process called photorespiration.

    <p>False (B)</p> Signup and view all the answers

    What is the primary CO2 acceptor in the C4 pathway?

    <p>phosphoenol pyruvate (PEP)</p> Signup and view all the answers

    In the C4 pathway, the first CO2 fixation product is ______ acid.

    <p>oxaloacetic</p> Signup and view all the answers

    Match the following types of plants with their characteristics:

    <p>C3 Plants = Fix CO2 through the Calvin cycle without special adaptations C4 Plants = Have Kranz anatomy and are more efficient in high temperatures Photorespiration = A wasteful process occurring in C3 plants Bundle Sheath Cells = Cells surrounding vascular bundles in C4 plants</p> Signup and view all the answers

    What is the primary function of RuBisCO in the Calvin cycle?

    <p>To catalyze the fixation of CO2 (C)</p> Signup and view all the answers

    Which of the following describes a key feature of C4 plants?

    <p>They require less water than C3 plants. (A)</p> Signup and view all the answers

    The formation of one molecule of glucose requires 6 turns of the Calvin cycle.

    <p>True (A)</p> Signup and view all the answers

    What are the three stages of the Calvin cycle?

    <p>Carboxylation, Reduction, Regeneration</p> Signup and view all the answers

    In C4 plants, the bundle sheath cells have intercellular spaces that facilitate gas exchange.

    <p>False (B)</p> Signup and view all the answers

    What anatomical feature is unique to C4 plants and is reflected in the term 'Kranz'?

    <p>special leaf anatomy or arrangement of bundle sheath cells</p> Signup and view all the answers

    During the reduction phase of the Calvin cycle, ________ molecules of ATP are required for each CO2 fixed.

    <p>2</p> Signup and view all the answers

    Match the processes in the Calvin cycle with their descriptions:

    <p>Carboxylation = CO2 combines with ribulose-1,5-bisphosphate Reduction = Formation of glucose from phosphorylated compounds Regeneration = Reformation of ribulose-1,5-bisphosphate</p> Signup and view all the answers

    What is a key role of NADPH in the Calvin cycle?

    <p>To reduce 3-phosphoglycerate to triose phosphate (C)</p> Signup and view all the answers

    ATP is not needed in the regeneration phase of the Calvin cycle.

    <p>False (B)</p> Signup and view all the answers

    The enzyme RuBisCO is correctly named as RuBP carboxylase-________.

    <p>oxygenase</p> Signup and view all the answers

    Which plants are known to benefit from increased CO2 concentration in terms of higher productivity?

    <p>C3 plants (A)</p> Signup and view all the answers

    C4 plants have a lower temperature optimum for photosynthesis compared to C3 plants.

    <p>False (B)</p> Signup and view all the answers

    What is the main reactant in the light reactions of photosynthesis?

    <p>water</p> Signup and view all the answers

    The photosystems used in the light reaction are known as _____ and _____.

    <p>PS I, PS II</p> Signup and view all the answers

    Match the type of plant with its photosynthesis characteristics:

    <p>C3 plants = Lower temperature optimum C4 plants = Higher temperature optimum Tropical plants = Higher temperature adaptation Temperate plants = Low temperature adaptation</p> Signup and view all the answers

    What is one consequence of water stress in plants?

    <p>Reduced carbon dioxide availability (A)</p> Signup and view all the answers

    The light reactions of photosynthesis occur in the stroma of chloroplasts.

    <p>False (B)</p> Signup and view all the answers

    What do mesophyll cells contain that is crucial for CO2 fixation during photosynthesis?

    <p>chloroplasts</p> Signup and view all the answers

    What is the primary role of the proton gradient across the thylakoid membrane?

    <p>To store energy for ATP synthesis. (B)</p> Signup and view all the answers

    Protons are released into the lumen as the primary accepter of electrons transfers electrons to an H carrier.

    <p>True (A)</p> Signup and view all the answers

    What enzyme reduces NADP+ to NADPH?

    <p>NADP reductase</p> Signup and view all the answers

    The __________ gradient created during photosynthesis is vital for ATP synthesis.

    <p>proton</p> Signup and view all the answers

    Match the components with their roles in creating the proton gradient.

    <p>Splitting of water = Produces protons in the lumen Photosystems = Transport electrons and protons NADP reductase = Reduces NADP+ CF0 = Facilitates proton movement through ATP synthase</p> Signup and view all the answers

    Where does the accumulation of protons occur during the process described?

    <p>In the lumen of the thylakoids. (D)</p> Signup and view all the answers

    The pH in the lumen of the thylakoids increases due to the accumulation of protons.

    <p>False (B)</p> Signup and view all the answers

    What part of the ATP synthase enzyme is embedded in the thylakoid membrane?

    <p>CF0</p> Signup and view all the answers

    What is the primary function of photosynthesis?

    <p>To produce chemical energy (C)</p> Signup and view all the answers

    Chlorophyll is the primary pigment responsible for photosynthesis in plants.

    <p>True (A)</p> Signup and view all the answers

    What gas is absorbed by plants during photosynthesis?

    <p>Carbon dioxide</p> Signup and view all the answers

    The process of photosynthesis converts light energy into __________ energy.

    <p>chemical</p> Signup and view all the answers

    Match the components necessary for photosynthesis with their roles:

    <p>Chlorophyll = Absorbs light energy Water = Provides electrons Carbon dioxide = Used to produce glucose Oxygen = Byproduct of photosynthesis</p> Signup and view all the answers

    Which part of the plant is primarily involved in photosynthesis?

    <p>Leaves (B)</p> Signup and view all the answers

    Photosynthesis occurs without the presence of light.

    <p>False (B)</p> Signup and view all the answers

    What key experiment demonstrates that starch is produced in the green parts of a leaf?

    <p>Testing variegated leaves or leaves covered with black paper</p> Signup and view all the answers

    How many types of pigments are involved in photosynthesis?

    <p>Four (A)</p> Signup and view all the answers

    Chlorophyll a is the only pigment responsible for capturing light energy in photosynthesis.

    <p>False (B)</p> Signup and view all the answers

    What color does Chlorophyll b appear in chromatograms?

    <p>yellow green</p> Signup and view all the answers

    Chlorophyll a absorbs light mainly in the ______ and ______ regions of the visible spectrum.

    <p>blue, red</p> Signup and view all the answers

    Match the following pigments with their colors:

    <p>Chlorophyll a = Bright or blue green Chlorophyll b = Yellow green Xanthophylls = Yellow Carotenoids = Yellow to yellow-orange</p> Signup and view all the answers

    What is the primary product of cyclic photophosphorylation?

    <p>ATP (A)</p> Signup and view all the answers

    Which pigment is considered the chief pigment associated with photosynthesis?

    <p>Chlorophyll a (D)</p> Signup and view all the answers

    Cyclic photophosphorylation only occurs when light of wavelengths below 680 nm is available.

    <p>False (B)</p> Signup and view all the answers

    Photosynthesis occurs at wavelengths where chlorophyll a does not absorb light.

    <p>False (B)</p> Signup and view all the answers

    What hypothesis explains the mechanism of ATP synthesis in chloroplasts?

    <p>Chemiosmotic hypothesis</p> Signup and view all the answers

    What method can be used to separate leaf pigments?

    <p>Paper chromatography</p> Signup and view all the answers

    In photosynthesis, protons accumulate towards the inside of the membrane, specifically in the ______.

    <p>lumen</p> Signup and view all the answers

    Match the following components with their functions in photosynthesis:

    <p>Photosystem I = Cyclic photophosphorylation ATP Synthase = ATP production Electron Transport Chain = Transfer of electrons NADP+ Reductase = NADPH production</p> Signup and view all the answers

    C4 plants exhibit a process called photorespiration.

    <p>False (B)</p> Signup and view all the answers

    Which of the following statements regarding proton accumulation in thylakoids is correct?

    <p>Protons accumulate in the lumen. (B)</p> Signup and view all the answers

    Chlorophyll is mainly present in the stroma lamellae of chloroplasts.

    <p>False (B)</p> Signup and view all the answers

    The arrangement of cells in C4 plants is referred to as __________ anatomy.

    <p>Kranz</p> Signup and view all the answers

    The excited electron in cyclic photophosphorylation is cycled back to the ______ complex.

    <p>PS I</p> Signup and view all the answers

    Match the following characteristics with C3 and C4 plants:

    <p>Higher temperature tolerance = C4 plants Higher levels of photorespiration = C3 plants Bundle sheath cells present = C4 plants Single fixation product is 3-carbon compound = C3 plants</p> Signup and view all the answers

    What is produced by the Calvin pathway?

    <p>Glucose (B)</p> Signup and view all the answers

    C4 plants primarily use the C3 pathway for biosynthesis.

    <p>False (B)</p> Signup and view all the answers

    How many NADPH molecules are required to produce one molecule of glucose through the Calvin cycle?

    <p>12</p> Signup and view all the answers

    The enzyme RuBisCO catalyzes both carboxylation and oxygenation reactions.

    <p>True (A)</p> Signup and view all the answers

    How many molecules of ATP and NADPH are utilized per CO2 molecule fixed in the Calvin cycle?

    <p>3 ATP and 2 NADPH</p> Signup and view all the answers

    To regenerate RuBP, the Calvin cycle requires one molecule of ________ for phosphorylation.

    <p>ATP</p> Signup and view all the answers

    Match the stages of the Calvin cycle with their key processes:

    <p>Carboxylation = CO2 combines with ribulose-1,5-bisphosphate Reduction = Carbohydrate formation Regeneration = Formation of RuBP</p> Signup and view all the answers

    What is the main product formed after six turns of the Calvin cycle?

    <p>Glucose (D)</p> Signup and view all the answers

    The Calvin cycle can continue indefinitely without the regeneration of RuBP.

    <p>False (B)</p> Signup and view all the answers

    What is the primary effect of higher CO2 concentrations on C3 plants?

    <p>Increased photosynthesis (C)</p> Signup and view all the answers

    What are the two primary energy molecules produced during the light-dependent reactions that are used in the Calvin cycle?

    <p>ATP and NADPH</p> Signup and view all the answers

    What role does water play in the process of photosynthesis?

    <p>Water serves as a reactant in light reactions and affects the availability of CO2.</p> Signup and view all the answers

    The light reactions of photosynthesis occur in the ________.

    <p>thylakoid membranes</p> Signup and view all the answers

    Match the following plant types with their characteristics regarding temperature optimum:

    <p>C3 Plants = Lower temperature optimum C4 Plants = Higher temperature optimum Tropical Plants = Higher temperature tolerance Temperate Plants = Lower temperature tolerance</p> Signup and view all the answers

    Which component absorbs light energy during the light reactions of photosynthesis?

    <p>Chlorophyll (A)</p> Signup and view all the answers

    The atmospheric CO2 provided during greenhouse cultivation has no effect on the yields of crops such as tomatoes.

    <p>False (B)</p> Signup and view all the answers

    What main product is formed during the light reactions of photosynthesis?

    <p>NADH</p> Signup and view all the answers

    What element did Melvin Calvin use to label carbon dioxide in his experiments?

    <p>C14 (C)</p> Signup and view all the answers

    Photosynthesis allows plants to synthesize food by utilizing energy from water only.

    <p>False (B)</p> Signup and view all the answers

    What is the primary process through which green plants synthesize their food?

    <p>photosynthesis</p> Signup and view all the answers

    Melvin Calvin won the Nobel Prize in ____ for his work on photosynthesis.

    <p>1961</p> Signup and view all the answers

    Match the following terms with their definitions:

    <p>Autotrophs = Organisms that synthesize their own food Heterotrophs = Organisms that depend on others for food Photosynthesis = The process of converting light energy into chemical energy C14 = A radioactive isotope of carbon used in tracking metabolic processes</p> Signup and view all the answers

    Which of the following statements best describes the significance of light in photosynthesis?

    <p>Light energy is converted into chemical energy during photosynthesis. (B)</p> Signup and view all the answers

    Name the two raw materials that plants primarily need for photosynthesis.

    <p>carbon dioxide and water</p> Signup and view all the answers

    All animals, including humans, are autotrophs.

    <p>False (B)</p> Signup and view all the answers

    What is the primary limiting factor for photosynthesis in most environments?

    <p>Carbon dioxide concentration (B)</p> Signup and view all the answers

    Light saturation occurs at 10 percent of full sunlight.

    <p>True (A)</p> Signup and view all the answers

    What effect does increasing light intensity have on photosynthesis beyond a certain point?

    <p>Breakdown of chlorophyll</p> Signup and view all the answers

    C3 plants show saturation in photosynthesis at approximately ________ µlL-1 of carbon dioxide concentration.

    <p>450</p> Signup and view all the answers

    Match the type of plant with their response to carbon dioxide concentrations:

    <p>C3 = Does not respond at low light C4 = Shows increase in high light</p> Signup and view all the answers

    What happens to the rate of photosynthesis when temperature is very low, even if other conditions are optimal?

    <p>Photosynthesis stops (D)</p> Signup and view all the answers

    C4 plants respond similarly to CO2 levels as C3 plants at low light conditions.

    <p>False (B)</p> Signup and view all the answers

    At what concentration of carbon dioxide do C4 plants show saturation?

    <p>360 µlL-1</p> Signup and view all the answers

    The primary function of chlorophyll a is to protect other pigments from photo-oxidation.

    <p>False (B)</p> Signup and view all the answers

    What are the high-energy chemical intermediates produced during the light reactions of photosynthesis?

    <p>ATP and NADPH</p> Signup and view all the answers

    The splitting of water during light reactions releases __________.

    <p>oxygen</p> Signup and view all the answers

    Match the following components of the light reactions with their functions:

    <p>Photosystem I = Light absorption and ATP production Photosystem II = Light absorption and NADPH production LHC = Pigment organization for light harvesting</p> Signup and view all the answers

    During which part of photosynthesis does water splitting occur?

    <p>Light reactions (A)</p> Signup and view all the answers

    What are the two types of light harvesting complexes in photosynthesis?

    <p>Photosystem I and Photosystem II</p> Signup and view all the answers

    Most photosynthesis occurs in the green region of the light spectrum.

    <p>False (B)</p> Signup and view all the answers

    Which of the following pigments is NOT involved in photosynthesis?

    <p>Melanin (B)</p> Signup and view all the answers

    Chlorophyll a is the only pigment responsible for photosynthesis.

    <p>False (B)</p> Signup and view all the answers

    Name the two primary colors of light that chlorophyll a absorbs most effectively.

    <p>Blue and red</p> Signup and view all the answers

    The structure within a chloroplast where the light-dependent reactions occur is called the ______.

    <p>thylakoid</p> Signup and view all the answers

    Match the following pigments with their characteristic colors:

    <p>Chlorophyll a = Bright or blue-green Chlorophyll b = Yellow-green Xanthophylls = Yellow Carotenoids = Yellow to yellow-orange</p> Signup and view all the answers

    What is the role of pigments in plants?

    <p>To absorb light at specific wavelengths (D)</p> Signup and view all the answers

    Chlorophyll b and carotenoids have the same absorption spectra as chlorophyll a.

    <p>False (B)</p> Signup and view all the answers

    The region of a chloroplast that contains ribosomes and is involved in the synthesis of proteins is known as the ______.

    <p>stroma</p> Signup and view all the answers

    What is the primary function of ATP synthase in the process of chemiosmosis?

    <p>To synthesize ATP from ADP and inorganic phosphate (C)</p> Signup and view all the answers

    The biosynthetic phase of photosynthesis directly depends on sunlight.

    <p>False (B)</p> Signup and view all the answers

    What is the first product formed during CO2 fixation as discovered by Melvin Calvin?

    <p>3-phosphoglyceric acid</p> Signup and view all the answers

    ATP and NADPH produced in the light reactions are used in the __________ phase of photosynthesis.

    <p>biosynthetic</p> Signup and view all the answers

    Match the product of the light reactions with its role:

    <p>ATP = Energy currency of the cell NADPH = Electron carrier O2 = Waste product released into the atmosphere 3-PGA = First product of CO2 fixation</p> Signup and view all the answers

    Which of the following components is critical for creating a proton gradient in chemiosmosis?

    <p>Proton pump (A)</p> Signup and view all the answers

    The Calvin cycle cannot occur in the absence of light.

    <p>False (B)</p> Signup and view all the answers

    How many carbon atoms are present in 3-phosphoglyceric acid?

    <p>3</p> Signup and view all the answers

    What is the role of PEP carboxylase in C4 plants?

    <p>It facilitates the initial CO2 fixation. (B)</p> Signup and view all the answers

    C4 plants perform the Calvin pathway exclusively in the mesophyll cells.

    <p>False (B)</p> Signup and view all the answers

    What are the 4-carbon compounds formed in mesophyll cells of C4 plants?

    <p>OAA, malic acid, aspartic acid</p> Signup and view all the answers

    The enzyme ________ is responsible for the fixation of CO2 in C3 plants.

    <p>RuBisCO</p> Signup and view all the answers

    Match the following enzymes with their respective roles.

    <p>RuBisCO = Fixes CO2 in C3 plants PEP carboxylase = Fixes CO2 in C4 plants Malate dehydrogenase = Converts OAA to malic acid Ribulose bisphosphate = Starting molecule for Calvin cycle</p> Signup and view all the answers

    Which of the following statements about photorespiration is accurate?

    <p>It occurs when RuBisCO binds O2 instead of CO2. (D)</p> Signup and view all the answers

    C4 plants have a higher competitive advantage for CO2 fixation compared to C3 plants under low light conditions.

    <p>False (B)</p> Signup and view all the answers

    In the Calvin cycle, the first product formed from RuBP and CO2 is ________.

    <p>3PGA</p> Signup and view all the answers

    What is the primary difference in CO2 fixation between C3 and C4 plants?

    <p>C4 plants utilize PEP carboxylase for initial CO2 fixation. (B)</p> Signup and view all the answers

    C4 plants do not experience photorespiration.

    <p>True (A)</p> Signup and view all the answers

    What is released during the photorespiratory pathway?

    <p>CO2</p> Signup and view all the answers

    In C4 plants, the primary CO2 acceptor is _____.

    <p>PEP</p> Signup and view all the answers

    C3 plants function better in high-temperature environments compared to C4 plants.

    <p>False (B)</p> Signup and view all the answers

    What is the unknown biological function of photorespiration?

    <p>Not known</p> Signup and view all the answers

    What is the primary role of photosystem II in the process of photosynthesis?

    <p>To provide electrons by splitting water (D)</p> Signup and view all the answers

    The Z scheme describes the transfer of electrons from photosystem I to the electron transport chain.

    <p>False (B)</p> Signup and view all the answers

    What are the end products formed from the splitting of water in photosystem II?

    <p>2H+, O2, and 4e−</p> Signup and view all the answers

    The process of synthesizing ATP from ADP and inorganic phosphate in the presence of light is called _______ phosphorylation.

    <p>photo</p> Signup and view all the answers

    Match the following components with their associated processes:

    <p>Photosystem II = Water splitting Photosystem I = Reduction of NADP+ Electron Transport Chain = ATP production Cyclic Photophosphorylation = ATP synthesis only</p> Signup and view all the answers

    In non-cyclic photophosphorylation, which photosystem is involved first?

    <p>Photosystem II (D)</p> Signup and view all the answers

    Oxygen released as a byproduct of photosynthesis comes from water molecules.

    <p>True (A)</p> Signup and view all the answers

    Name the primary energy carrier synthesized through phosphorylation processes in cells.

    <p>ATP</p> Signup and view all the answers

    What is the primary benefit of growing C3 plants in a CO2 enriched atmosphere?

    <p>Increased photosynthesis rates (B)</p> Signup and view all the answers

    What effect does water stress have on a plant's stomata?

    <p>It causes the stomata to close.</p> Signup and view all the answers

    The light reaction of photosynthesis occurs in the __________ of chloroplasts.

    <p>thylakoid membranes</p> Signup and view all the answers

    Match the photosynthesis processes to their sites of occurrence.

    <p>Light Reactions = Thylakoid membranes Calvin Cycle = Stroma</p> Signup and view all the answers

    What is the primary product of the light reaction in photosynthesis?

    <p>Oxygen (B)</p> Signup and view all the answers

    Photosynthesis occurs only in the green parts of the plants, primarily the flowers.

    <p>False (B)</p> Signup and view all the answers

    Identify one of the two photosystems involved in the light reactions.

    <p>Photosystem I or Photosystem II</p> Signup and view all the answers

    The reaction centre of Photosystem II is called P680.

    <p>True (A)</p> Signup and view all the answers

    What is the role of pigment molecules in the light harvesting complex?

    <p>To absorb different wavelengths of light.</p> Signup and view all the answers

    The electrons from Photosystem II are transferred to an electron ________ that forms part of the electron transport system.

    <p>acceptor</p> Signup and view all the answers

    Match the photosystems with their absorption peak:

    <p>Photosystem I = P700 Photosystem II = P680</p> Signup and view all the answers

    What happens to electrons in Photosystem I after they are excited?

    <p>They are transferred to another electron acceptor. (B)</p> Signup and view all the answers

    Both photosystems participate in cyclic photophosphorylation.

    <p>False (B)</p> Signup and view all the answers

    Which molecule is produced as a result of the electron transport chain in photosynthesis?

    <p>NADPH</p> Signup and view all the answers

    What substance in plants is primarily responsible for glucose production during photosynthesis?

    <p>Chlorophyll (B)</p> Signup and view all the answers

    Photosynthesis in green plants relies on hydrogen from carbon dioxide.

    <p>False (B)</p> Signup and view all the answers

    What is the empirical equation representing the process of photosynthesis in oxygen-evolving organisms?

    <p>CO2 + H2O → [CH2O] + O2</p> Signup and view all the answers

    The visible light spectrum that demonstrates the effective wavelengths for photosynthesis includes __________ light.

    <p>blue and red</p> Signup and view all the answers

    Match the contributions to photosynthesis with the corresponding scientist:

    <p>Julius von Sachs = Discovered glucose production. T.W. Engelmann = Identified action spectrum of photosynthesis. Cornelius van Niel = Proved the oxygen source in photosynthesis. Joseph Priestley = Demonstrated that plants release oxygen.</p> Signup and view all the answers

    Which hydrogen donor is used by purple and green sulfur bacteria during photosynthesis?

    <p>Hydrogen sulfide (B)</p> Signup and view all the answers

    The process of photosynthesis involves the reduction of carbon dioxide to carbohydrates.

    <p>True (A)</p> Signup and view all the answers

    What component is oxidized to oxygen during photosynthesis in green plants?

    <p>Water (H2O)</p> Signup and view all the answers

    What is the first product of CO2 fixation in C4 plants?

    <p>4-carbon compound (B)</p> Signup and view all the answers

    RuBisCO only functions as a carboxylase in C3 plants.

    <p>False (B)</p> Signup and view all the answers

    What molecule is converted to produce 2 molecules of 3-carbon PGA in the carbon fixation cycle?

    <p>RuBP</p> Signup and view all the answers

    The process by which C3 plants convert oxygen instead of carbon dioxide is called ________.

    <p>photorespiration</p> Signup and view all the answers

    Match the following types of plants with their characteristic photosynthesis pathways:

    <p>C3 plants = Fix CO2 directly in the Calvin cycle C4 plants = Initial fixation results in a 4-carbon compound C3 pathway = Most common pathway in temperate climates C4 pathway = More efficient in hot, dry environments</p> Signup and view all the answers

    Which statement is true regarding chlorophyll b's role in photosynthesis?

    <p>Chlorophyll b assists chlorophyll a in capturing light energy. (A)</p> Signup and view all the answers

    The light reaction of photosynthesis produces ATP and NADPH, which are utilized in the Calvin cycle.

    <p>True (A)</p> Signup and view all the answers

    What is the primary function of RuBisCO during the process of carbon fixation?

    <p>It catalyzes the addition of CO2 to RuBP.</p> Signup and view all the answers

    What is the primary outcome of the photorespiratory pathway?

    <p>Release of CO2 (B)</p> Signup and view all the answers

    C4 plants do not exhibit photorespiration.

    <p>True (A)</p> Signup and view all the answers

    What is the main function of RuBisCO in C4 plants?

    <p>Carboxylase activity</p> Signup and view all the answers

    C4 acids are broken down in the __________ cells to release CO2.

    <p>bundle sheath</p> Signup and view all the answers

    Match the characteristics with C3 and C4 plants:

    <p>RuBP as primary CO2 acceptor = C3 Plants Has PEP Case = C4 Plants Photorespiration occurs = C3 Plants Higher yield in hot climates = C4 Plants</p> Signup and view all the answers

    Which of the following statements is true regarding ATP synthesis in the photorespiratory pathway?

    <p>ATP synthesis is completely absent. (C)</p> Signup and view all the answers

    The biological function of photorespiration is well understood.

    <p>False (B)</p> Signup and view all the answers

    What contributes to the better productivity in C4 plants?

    <p>Increased concentration of CO2 at the enzyme site</p> Signup and view all the answers

    What process do green plants use to make food?

    <p>Photosynthesis (A)</p> Signup and view all the answers

    All living forms on Earth depend on sunlight for energy.

    <p>True (A)</p> Signup and view all the answers

    Who won the Nobel Prize in 1961 for mapping the pathway of carbon assimilation in photosynthesis?

    <p>Melvin Calvin</p> Signup and view all the answers

    Green plants are called ________ because they can synthesize their own food.

    <p>autotrophs</p> Signup and view all the answers

    Match the following substances involved in photosynthesis with their role:

    <p>Carbon dioxide = Raw material for food synthesis Water = Source of electrons Light energy = Drives the synthesis process Glucose = Main product of photosynthesis</p> Signup and view all the answers

    What did Melvin Calvin and J.A. Bassham use to study reactions in green plants?

    <p>C14 (A)</p> Signup and view all the answers

    Plants are heterotrophs because they depend on others for food.

    <p>False (B)</p> Signup and view all the answers

    What is the main energy transformation that occurs during photosynthesis?

    <p>Light energy to chemical energy</p> Signup and view all the answers

    What did Joseph Priestley conclude about plants during his experiments?

    <p>Plants restore the air damaged by breathing animals and burning candles. (A)</p> Signup and view all the answers

    Jan Ingenhousz demonstrated that plants can produce oxygen in both sunlight and darkness.

    <p>False (B)</p> Signup and view all the answers

    What type of plant did Ingenhousz use in his experiment to show the production of oxygen?

    <p>an aquatic plant</p> Signup and view all the answers

    In Priestley's experiment, the ________ was used to demonstrate the role of air in supporting life.

    <p>bell jar</p> Signup and view all the answers

    Match the following scientists with their contributions:

    <p>Joseph Priestley = Demonstrated the role of air in plant growth Jan Ingenhousz = Showed sunlight is essential for oxygen production Julius von Sachs = Demonstrated glucose production in plants Cornelius van Niel = Studied light-dependent reactions</p> Signup and view all the answers

    What was one of the key observations made by Priestley during his experiments?

    <p>A mint plant can revive a suffocating mouse. (D)</p> Signup and view all the answers

    Ingenhousz's experiments confirmed that sunlight is not necessary for photosynthesis.

    <p>False (B)</p> Signup and view all the answers

    Priestley discovered ________ in 1774, leading to his findings on plant respiration.

    <p>oxygen</p> Signup and view all the answers

    What does the equation of photosynthesis ultimately produce?

    <p>Glucose (C)</p> Signup and view all the answers

    In photosynthesis, what are the two types of reactions involved?

    <p>Light reactions and dark reactions</p> Signup and view all the answers

    In the chloroplasts, ATP and NADPH are produced during the ______ reactions.

    <p>light</p> Signup and view all the answers

    Match the following components of the chloroplast with their function:

    <p>Grana = Sites of light reactions Stroma = Site of dark reactions Thylakoid membranes = Contain chlorophyll Matrix stroma = Enzymatic reactions for sugar synthesis</p> Signup and view all the answers

    What is the expected CO2 fixation rate under high light conditions?

    <p>High (D)</p> Signup and view all the answers

    Where in the chloroplast does the Calvin cycle occur?

    <p>In the stroma (B)</p> Signup and view all the answers

    The O2 released during photosynthesis comes from carbon dioxide.

    <p>False (B)</p> Signup and view all the answers

    Photorespiration is negligible at high light intensities.

    <p>True (A)</p> Signup and view all the answers

    What alignment do chloroplasts take for optimal light absorption?

    <p>Chloroplasts align flat surfaces parallel to the walls of the mesophyll cells.</p> Signup and view all the answers

    What temperature range is considered optimal for photosynthesis?

    <p>30-40 C</p> Signup and view all the answers

    Photorespiration becomes ______ at low CO2 concentrations.

    <p>high</p> Signup and view all the answers

    Match each condition with its effect on photorespiration:

    <p>Low light intensity = High photorespiration High light intensity = Negligible photorespiration Low CO2 concentration = High photorespiration High CO2 concentration = Negligible photorespiration</p> Signup and view all the answers

    Which internal plant factors influence the rate of photosynthesis?

    <p>Chlorophyll amount and leaf size (B)</p> Signup and view all the answers

    Blackman’s Law of Limiting Factors states that multiple factors can limit a process simultaneously.

    <p>False (B)</p> Signup and view all the answers

    Plants generally perform better photosynthesis above _______ °C.

    <p>30-40</p> Signup and view all the answers

    What is the first product formed during the fixation of CO2 as discovered by Melvin Calvin?

    <p>3-Phosphoglyceric acid (A)</p> Signup and view all the answers

    The biosynthetic phase of photosynthesis can occur in the absence of light.

    <p>True (A)</p> Signup and view all the answers

    How many carbon atoms are in 3-phosphoglyceric acid?

    <p>3</p> Signup and view all the answers

    Chemiosmosis requires a membrane, a _____ pump, a proton gradient, and ATP synthase.

    <p>proton</p> Signup and view all the answers

    Which of the following components is essential for synthesizing ATP in the photosynthetic process?

    <p>Proton gradient (A)</p> Signup and view all the answers

    Match the following processes with their descriptions:

    <p>Calvin Cycle = CO2 fixation to synthesize sugars Light Reaction = Production of ATP and NADPH Chemiosmosis = Proton gradient-driven ATP synthesis Cycle of Photosynthesis = Main pathways introduced by Melvin Calvin</p> Signup and view all the answers

    Oxygen produced during the light reactions diffuses out of the chloroplast.

    <p>True (A)</p> Signup and view all the answers

    The biosynthetic phase of photosynthesis uses ATP and _____ to drive the synthesis of food.

    <p>NADPH</p> Signup and view all the answers

    Flashcards

    Cyclic photophosphorylation

    A type of photosynthesis where electrons are cycled back to photosystem I, producing ATP but not NADPH.

    Photosystem I (PS I)

    A protein complex in the thylakoid membrane that absorbs light energy and transfers electrons in photosynthesis.

    Electron transport chain (ETC)

    A series of protein complexes in the thylakoid membrane that transfer electrons from photosystem II to photosystem I, creating a proton gradient.

    Chemiosmotic hypothesis

    A theory explaining ATP synthesis in chloroplasts and mitochondria, linking it to a proton gradient across a membrane.

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    Thylakoid membrane

    Location in chloroplasts where the light-dependent reactions of photosynthesis occur, including the electron transport chain.

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    NADPH

    An electron carrier used in photosynthesis to provide energy for the Calvin cycle.

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    Proton gradient

    Difference in proton concentration across a membrane used to drive ATP synthesis.

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    ATP synthesis

    Process of creating adenosine triphosphate, a molecule used for energy by the cell.

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    Priestley's Experiment

    Priestley's experiment investigated the role of air in plant growth. He observed that burning candles and breathing animals damaged the air, but plants restored it.

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    Oxygen's Role

    Burning and breathing use up oxygen in the air, but plants produce it.

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    Ingenhousz's experiment

    Ingenhousz demonstrated that sunlight is essential for plants to purify the air, producing oxygen.

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    Sunlight's Importance

    Sunlight is crucial for photosynthesis, the process by which plants produce oxygen.

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    Photosynthesis

    The process in which plants use sunlight to produce food and oxygen.

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    Oxygen Production

    Plants release oxygen as a byproduct of photosynthesis.

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    Bell Jar Experiment

    A controlled experiment using a closed glass jar to study gases and reactions.

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    Early Photosynthesis Experiments

    Early experiments by Priestley and Ingenhousz laid the groundwork for our understanding of how plants produce oxygen through the process of photosynthesis.

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    CO2 fixation rate under high light

    The speed at which a plant converts carbon dioxide into sugars during photosynthesis when exposed to intense sunlight.

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    Photorespiration at low light

    Photorespiration is negligible at low light intensities because the Calvin cycle operates at a slower pace, minimizing the chances of oxygen being used as a substrate by RuBisCo.

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    Photorespiration at high light

    Photorespiration is present, but at a lower rate, at high light intensities because the Calvin cycle operates more efficiently, reducing the chance of oxygen binding to RuBisCo.

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    Photorespiration at low CO2

    Photorespiration is high at low CO2 concentrations because RuBisCo is more likely to bind to oxygen instead of carbon dioxide.

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    Photorespiration at high CO2

    Photorespiration is negligible at high CO2 concentrations because RuBisCo preferentially binds to carbon dioxide, minimizing oxygen binding and wasteful reactions.

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    Optimal temperature for photosynthesis

    The temperature range where photosynthesis occurs at its peak rate, typically between 30-40°C for most plants.

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    Kranz anatomy

    A specialized leaf structure found in C4 plants, characterized by a ring of mesophyll cells surrounding a bundle sheath cell.

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    How to identify C4 plants

    Examine cross-sections of leaves under a microscope to observe the presence of Kranz anatomy—a ring of mesophyll cells encircling a bundle sheath cell.

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    Who proved that oxygen comes from water?

    Cornelius van Niel, a microbiologist, proved that oxygen produced during photosynthesis comes from water, not carbon dioxide. He used a different hydrogen donor (H2S) for purple and green sulfur bacteria to investigate this.

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    What is photosynthesis?

    Photosynthesis is the process used by plants and some bacteria to convert light energy into chemical energy in the form of glucose. It uses carbon dioxide and water as raw materials, producing oxygen as a byproduct.

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    What is the empirical equation for photosynthesis?

    The equation CO2 + H2O → [CH2O] + O2 represents the overall process of photosynthesis. It shows that carbon dioxide and water are combined using light energy to produce carbohydrates (like glucose) and oxygen.

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    Who discovered the importance of chlorophyll?

    Julius von Sachs discovered that chlorophyll, the green pigment in plants, is located in chloroplasts within plant cells and is essential for glucose production during photosynthesis.

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    What is the role of chlorophyll?

    Chlorophyll absorbs light energy, particularly in the blue and red wavelengths of the spectrum. This energy is used to power the reactions of photosynthesis.

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    What is the action spectrum of photosynthesis?

    The action spectrum of photosynthesis shows the relative effectiveness of different wavelengths of light in driving photosynthesis. It resembles the absorption spectrum of chlorophyll a and b, indicating their key role in capturing light for the process.

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    What is the role of bacteria in Engelmann's experiment?

    Engelmann used aerobic bacteria to detect the sites of oxygen evolution in a green alga. The bacteria accumulated mainly in the regions illuminated by blue and red light, demonstrating that these wavelengths were most effective for photosynthesis.

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    What is the importance of T.W. Engelmann's experiment?

    Engelmann's experiment using a prism and aerobic bacteria helped discover the action spectrum of photosynthesis. He showed that certain wavelengths of light were more effective than others in driving the process.

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    PEP carboxylase

    An enzyme that catalyzes the initial fixation of CO2 in C4 plants, forming oxaloacetate (OAA).

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    C4 acid

    A four-carbon compound, like malic acid or aspartic acid, formed in mesophyll cells of C4 plants after CO2 fixation.

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    Bundle sheath cells

    Specialized cells surrounding the vascular bundles in C4 plants, where CO2 is released from C4 acids and enters the Calvin cycle.

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    RuBisCO

    An enzyme that catalyzes the first step of the Calvin cycle, where CO2 is incorporated into RuBP.

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    Photorespiration

    A process in plants where RuBisCO binds to oxygen instead of carbon dioxide, leading to the breakdown of RuBP and the release of CO2.

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    What makes RuBisCO unique?

    RuBisCO can bind to both CO2 and O2, making its activity dependent on the relative concentrations of these gases.

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    How does CO2 concentration impact RuBisCO?

    Higher CO2 concentration favors CO2 binding to RuBisCO, increasing photosynthesis and reducing photorespiration.

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    How does photorespiration differ in C3 and C4 plants?

    C3 plants exhibit higher photorespiration than C4 plants due to the relative concentrations of CO2 and O2 in their chloroplasts.

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    C4 pathway

    A type of photosynthesis found in some tropical plants where the first product of CO2 fixation is a 4-carbon compound. This occurs in mesophyll cells, followed by the Calvin cycle in bundle sheath cells.

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    C3 plants

    Plants where the first product of CO2 fixation is a 3-carbon compound (PGA). They are most common but can face photorespiration in hot, sunny conditions.

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    Calvin cycle

    The series of biochemical reactions that take place in the stroma of chloroplasts to convert CO2 into sugar (glucose) using ATP and NADPH produced during the light-dependent reactions.

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    Mesophyll cells

    Cells in the leaf where photosynthesis primarily occurs, containing chloroplasts and carrying out the initial CO2 fixation in C4 plants.

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    Light-dependent reactions

    The first stage of photosynthesis which occurs in the thylakoid membrane of chloroplasts, converting light energy into chemical energy (ATP and NADPH).

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    Autotroph

    An organism that can produce its own food by using light energy, like plants.

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    Heterotroph

    An organism that cannot produce its own food and relies on consuming other organisms for energy, like animals.

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    Chlorophyll

    A green pigment in plants that absorbs light energy, particularly in the blue and red wavelengths, which is used to power photosynthesis.

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    Photosynthesis: The Basics

    Photosynthesis is a process plants use to trap and convert light energy into chemical energy (food). This chemical energy is stored in sugars, which are the plant's primary way of storing energy.

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    Why is Photosynthesis Important?

    Photosynthesis is essential for life on Earth because:

    1. Food Source: It produces the primary source of food for most organisms, both directly and indirectly.
    2. Oxygen Production: It releases oxygen into the atmosphere, which is crucial for respiration in most living beings.
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    Photosynthesis Requires...

    Photosynthesis needs:

    1. Chlorophyll: The green pigment that absorbs light energy.
    2. Light: Energy source.
    3. CO2: Carbon dioxide from the air.
    4. Water: Used to create sugar.
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    Experiment: Starch Test

    This experiment shows that leaves produce starch (a form of sugar) in the presence of light. Variegated leaves or leaves partially covered with paper demonstrate that only green parts of the leaf produce starch.

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    Experiment: CO2 & Starch

    This experiment shows that CO2 is essential for photosynthesis. A leaf partially enclosed in a CO2 absorbing solution produces less starch compared to the exposed part.

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    Oxygen: A Byproduct

    Oxygen is released as a waste product during photosynthesis. It's the result of splitting water molecules to get the hydrogen needed for sugar production.

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    Photosynthesis: Two Stages

    Photosynthesis takes place in two main stages:

    1. Light-Dependent Reactions: Use light energy to produce ATP (energy currency) and NADPH (high-energy electron carrier).
    2. Light-Independent Reactions (Calvin Cycle): Use ATP and NADPH to convert CO2 into sugar using the Calvin cycle, which is named after the scientist who discovered it.
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    Chloroplasts: Photosynthesis Headquarters

    Chloroplasts are organelles found inside plant cells. They contain stacks of thylakoids (where light-dependent reactions occur) and a fluid-filled stroma (where the Calvin Cycle takes place).

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    Photosynthesis Equation

    The overall equation for photosynthesis is 6CO2 + 12H2O → C6H12O6 + 6H2O + 6O2. This represents the conversion of carbon dioxide and water into glucose, water, and oxygen using light energy.

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    Where does photosynthesis occur?

    Photosynthesis takes place primarily in the chloroplasts of green leaves, but it can also occur in other green parts of plants like stems.

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    Chloroplast Alignment

    Chloroplasts align themselves along the walls of mesophyll cells to maximize light absorption. In bright light, they align parallel to the walls. In dim light, they align perpendicular to the incident light.

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    Light Reactions

    Light reactions, also called photochemical reactions, occur in the membrane system of chloroplasts. They capture light energy to produce ATP and NADPH.

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    Dark Reactions

    Dark reactions, also called carbon reactions, occur in the stroma of chloroplasts. They use ATP and NADPH from light reactions to synthesize glucose.

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    Oxygen Source

    The oxygen released during photosynthesis comes from water, not carbon dioxide. This was proven using radioactive isotopes.

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    What is the role of the membrane system in chloroplasts?

    The membrane system of chloroplasts is responsible for capturing light energy and producing ATP and NADPH using light-dependent reactions.

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    What is the role of the stroma in chloroplasts?

    The stroma of chloroplasts is the site of dark reactions, where ATP and NADPH from light reactions are used to synthesize glucose.

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    What drives the movement of electrons in the ETC?

    The movement of electrons through the electron transport chain is driven by their redox potential, flowing from molecules with lower redox potential to those with higher redox potential.

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    NADP+ to NADPH

    NADP+ is an electron carrier that accepts electrons at the end of the electron transport chain, becoming NADPH, a reduced form with higher energy.

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    Light-Dependent Reactions: Summary

    The light-dependent reactions of photosynthesis occur in the thylakoid membrane, using light energy to generate ATP and NADPH. This process involves absorbing light, exciting electrons, and moving them through a chain of carriers to create a proton gradient that powers ATP synthesis.

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    Why are C4 plants more efficient in hot environments?

    C4 plants minimize photorespiration by concentrating CO2 in bundle sheath cells, allowing RuBisCO to function more efficiently even in high temperatures.

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    What is the difference between light-dependent and light-independent reactions?

    Light-dependent reactions use light energy to create ATP and NADPH in the thylakoid membrane. Light-independent reactions use this energy to convert CO2 into sugar in the stroma.

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    What is the importance of chlorophyll in photosynthesis?

    Chlorophyll absorbs light energy in the blue and red wavelengths, which is crucial for exciting electrons that fuel the light-dependent reactions of photosynthesis.

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    Limiting Factor

    The factor that most directly restricts a chemical process's rate when it's affected by multiple factors. This factor will be closest to its minimal value, and changing its quantity will directly impact the process.

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    Light Intensity and Photosynthesis

    At low light intensities, photosynthesis rate increases linearly with light intensity. However, at higher intensities, the rate plateaus as other factors become limiting.

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    Light Saturation Point

    The point where increasing light intensity no longer increases the rate of photosynthesis. This occurs at about 10% of full sunlight for most plants.

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    CO2 Limitation

    Carbon dioxide is a major limiting factor for photosynthesis, as atmospheric concentrations are relatively low. Increasing CO2 levels can boost photosynthesis up to a certain point, after which it becomes harmful.

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    C3 vs C4 Plants & CO2

    C3 plants saturate at higher CO2 concentrations (~450 µlL-1) compared to C4 plants (~360 µlL-1). This makes C3 plants more sensitive to current low CO2 levels.

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    Optimal Temperature

    The specific temperature range where a plant's photosynthesis rate is maximized. Outside this range, the rate decreases.

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    Chloroplast Structure

    Chloroplasts are organelles in plant cells where photosynthesis takes place. They have an outer and inner membrane, a fluid-filled stroma, and stacks of thylakoid membranes.

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    Stroma

    The stroma is the fluid-filled space inside a chloroplast that surrounds the thylakoid membranes. The Calvin cycle, which converts CO2 into sugar, takes place in the stroma.

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    Four Leaf Pigments

    Plant leaves contain four pigments: chlorophyll a (blue-green), chlorophyll b (yellow-green), xanthophylls (yellow), and carotenoids (yellow-orange).

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    Action Spectrum of Photosynthesis

    The action spectrum shows the relative effectiveness of different wavelengths of light in driving photosynthesis. It resembles the absorption spectrum of chlorophyll a and b.

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    Oxygen Source in Photosynthesis

    The oxygen released during photosynthesis comes from the breakdown of water, not from carbon dioxide.

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    RuBisCO Function in C4 Plants

    In C4 plants, RuBisCO primarily functions as a carboxylase (binding CO2), minimizing the oxygenase activity (binding oxygen).

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    C3 vs. C4: CO2 Acceptor

    C3 plants use RuBP (5 carbons) as the primary CO2 acceptor, while C4 plants use PEP (3 carbons).

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    C3 vs. C4: Initial Carboxylation

    In C3 plants, initial carboxylation occurs in mesophyll cells. In C4 plants, initial carboxylation occurs in mesophyll cells, but the Calvin cycle occurs in bundle sheath cells.

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    First Product of CO2 Fixation

    The initial stable organic compound produced when carbon dioxide is incorporated into a plant during photosynthesis.

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    RuBP

    Ribulose bisphosphate, a 5-carbon sugar that acts as the primary CO2 acceptor in the Calvin Cycle.

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    Carboxylation

    The process of adding CO2 to a molecule, specifically RuBP in the Calvin Cycle, to form a 3-carbon compound.

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    3-PGA

    3-phosphoglyceric acid, a 3-carbon compound formed during carboxylation in the Calvin cycle.

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    What is the role of ATP and NADPH in the Calvin cycle?

    ATP provides the energy needed to drive the reactions of the Calvin cycle, while NADPH provides the reducing power to convert CO2 into sugar.

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    Regeneration in the Calvin cycle

    The final stage of the Calvin cycle where the CO2 acceptor, ribulose-1,5-bisphosphate (RuBP), is regenerated.

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    Why are 6 turns of the Calvin cycle needed to produce one glucose molecule?

    Each turn of the Calvin cycle fixes one molecule of CO2. Since glucose has six carbon atoms, six turns are required to assemble the necessary carbon atoms.

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    How does the Calvin cycle rely on the light-dependent reactions?

    The Calvin cycle relies on the light-dependent reactions to provide the ATP and NADPH needed to power the reactions that convert CO2 into sugar.

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    What is the difference between C3 and C4 plants?

    C3 plants are the most common type and fix CO2 directly into a 3-carbon compound. C4 plants have an additional step that concentrates CO2 in a specialized cell, increasing the efficiency of photosynthesis. This makes them more efficient in hot, sunny environments.

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    PEP Carboxylase (PEPcase)

    The enzyme responsible for initially fixing carbon dioxide in C4 plants. It catalyzes the conversion of PEP to oxaloacetate, a 4-carbon compound.

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    RuBisCO's Dual Nature

    RuBisCO, the enzyme responsible for carbon fixation, can bind to both CO2 and O2. Its affinity for CO2 is higher, but in C3 plants, some O2 can bind, leading to photorespiration.

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    Why does Photorespiration decrease at high CO2 levels?

    At high CO2 levels, RuBisCO is more likely to bind to CO2, decreasing the chance of it binding to O2, which reduces photorespiration. This is because CO2 and O2 are competing for binding sites on RuBisCO.

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    What is the advantage of C4 plants over C3 plants in hot environments?

    C4 plants have adapted to minimize photorespiration by efficiently concentrating CO2 in their bundle sheath cells. This allows RuBisCO to function more efficiently in hot conditions, leading to higher photosynthetic rates.

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    Stroma lamellae

    The thylakoid membranes in chloroplasts that lack PS II and NADP reductase. This allows for cyclic photophosphorylation to occur.

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    Proton gradient in chloroplasts

    A difference in proton concentrations across the thylakoid membrane. Protons accumulate inside due to electron transport, creating a potential energy source.

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    Where is ATP produced?

    ATP synthesis is linked to the proton gradient across the thylakoid membrane in chloroplasts. This is analogous to the mitochondrial membrane in respiration.

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    How does PS II differ from PS I?

    Photosystem II (PS II) absorbs light energy and uses it to split water molecules, releasing oxygen and transferring electrons. Photosystem I (PS I) captures light energy and uses it to create NADPH + H+.

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    What drives electron flow in photosynthesis?

    Electron flow in photosynthesis is driven by a series of redox reactions as electrons move from molecules with lower redox potential to those with higher redox potential.

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    Proton Gradient Across Thylakoid Membrane

    The difference in proton concentration between the lumen (inside) of the thylakoid and the stroma (outside). This gradient is created by the movement of protons across the membrane during the light-dependent reactions.

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    Proton Movement During Electron Transport

    As electrons move through the electron transport chain, protons are transported across the thylakoid membrane. This occurs because an H+ carrier accepts electrons and releases protons into the lumen.

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    NADP+ Reductase

    An enzyme responsible for reducing NADP+ to NADPH using electrons from PS I and protons from the stroma.

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    pH Gradient

    The proton gradient across the thylakoid membrane results in a lower pH (more acidic) in the lumen compared to the stroma.

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    Proton Gradient and ATP Synthesis

    The proton gradient provides the energy for ATP synthesis. As protons move from the lumen to the stroma through the ATP synthase, energy is released, driving the formation of ATP.

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    ATP Synthase Structure

    ATP synthase is composed of two parts: CF0 embedded in the thylakoid membrane and CF1 protruding into the stroma. CF0 forms a channel for proton movement, while CF1 performs ATP synthesis.

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    Role of ATP in Photosynthesis

    ATP is the energy currency of the cell. It is produced during the light-dependent reactions and used in the Calvin cycle to convert CO2 into sugar.

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    Role of Sunlight in Proton Gradient

    Sunlight initiates the flow of electrons and protons across the thylakoid membrane, ultimately creating the proton gradient that drives ATP synthesis.

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    Action Spectrum

    The action spectrum shows the effectiveness of different wavelengths of light in driving photosynthesis. It aligns strongly with the absorption spectrum of chlorophyll a and b.

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    Chlorophyll a & b

    The primary pigments in photosynthesis. Chlorophyll a absorbs mainly blue and red light, chlorophyll b absorbs mainly blue and orange light.

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    Accessory Pigments

    Pigments other than chlorophyll a that help capture light energy and transfer it to chlorophyll a. These pigments include chlorophyll b, carotenoids, and xanthophylls.

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    Photo-oxidation

    Damage to chlorophyll a caused by excessive light exposure. Accessory pigments protect chlorophyll a from this damage.

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    ATP & NADPH

    High-energy molecules produced during the light reactions. ATP is the cell's primary energy currency, and NADPH carries reducing power for reactions.

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    Chemiosmosis

    The process of using a proton gradient to drive ATP synthesis, involving a membrane, a proton pump, a proton gradient, and ATP synthase.

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    Biosynthetic Phase of Photosynthesis

    The process of using ATP and NADPH from the light-dependent reactions to synthesize sugar in the Calvin cycle.

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    What are the advantages of C4 plants?

    C4 plants benefit from their specialized pathway, which allows them to thrive in hot, dry environments. They maximize photosynthetic efficiency by concentrating CO2 in bundle sheath cells, minimizing photorespiration. This allows them to outcompete C3 plants in these harsh conditions.

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    Z scheme

    The pathway of electron flow during the light-dependent reactions of photosynthesis, characterized by its zigzag shape when plotted on a redox potential scale.

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    Water splitting

    The process in which water molecules are broken down to release electrons, protons, and oxygen during the light-dependent reactions of photosynthesis.

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    Non-cyclic photo-phosphorylation

    The synthesis of ATP using light energy by the flow of electrons from Photosystem II through an electron transport chain to Photosystem I, ultimately reducing NADP+ to NADPH.

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    Photo-phosphorylation

    The process of ATP synthesis using light energy in chloroplasts.

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    Redox potential

    A measure of a molecule's tendency to gain or lose electrons. A higher redox potential indicates a greater tendency to gain electrons.

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    Thylakoid lumen

    The space inside the thylakoid membrane in chloroplasts where protons accumulate during the light-dependent reactions.

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    Proton Movement

    Protons move across the thylakoid membrane from the lumen (high concentration) to the stroma (low concentration) through the CF0 channel of ATP synthase.

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    Electron Transport Chain

    Protons are transported across the membrane as electrons move through the photosystems, particularly during the transfer from the primary electron acceptor to the H carrier.

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    C4 vs C3 Plants

    C4 plants have evolved a special pathway that minimizes photorespiration, making them more efficient in hot, dry climates. C3 plants are the most common type and are less efficient in hot, dry conditions.

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    C3 Plants and CO2

    C3 plants show increased photosynthesis rates and higher productivity when exposed to higher CO2 concentrations. This is used in greenhouses for crops like tomatoes and bell peppers.

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    Temperature & Photosynthesis

    Enzymatic reactions, like the dark reactions of photosynthesis, are temperature-sensitive. C4 plants thrive in higher temperatures, while C3 plants have a lower temperature optimum.

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    Water Stress Effects

    Water stress causes stomata to close, reducing CO2 availability. This, combined with wilting leaves, hinders photosynthesis.

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    Light Reaction Site

    The light-dependent reactions of photosynthesis happen on the membranes within chloroplasts.

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    Stroma & Carbon Fixation

    The stroma within chloroplasts is where the carbon-fixing reactions (Calvin cycle) occur, transforming CO2 into sugars.

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    Photosystems: PS I & PS II

    There are two photosystems (PS I and PS II) in photosynthesis. PS I uses P700 chlorophyll, while PS II uses P680 chlorophyll for light absorption.

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    Electron Flow & NADPH

    Light energy excites electrons, which travel through PS II and PS I, ending up on NADP+ to form NADPH.

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    CO2 Fixation

    The process of incorporating carbon dioxide into an organic molecule, primarily RuBP in the Calvin Cycle, to create a stable carbon compound.

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    Light of Wavelengths Beyond 680 nm

    Cyclic photophosphorylation can occur when only light of wavelengths beyond 680 nm are available for excitation. This suggests PS II is not active, leading to a 'short circuit' of electron flow.

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    PS I Functional Only

    Cyclic photophosphorylation is observed when only PS I is functional. The electron is circulated within the photosystem, leading to ATP synthesis without NADPH production.

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    Location of Cyclic Photophosphorylation

    Cyclic photophosphorylation likely occurs in the stroma lamellae, which lack PS II and NADP reductase, suggesting a specialized pathway for ATP production.

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    What are carotenoids and xanthophylls?

    Carotenoids are pigments that absorb blue-violet light, appearing yellow-orange. Xanthophylls are yellow pigments that mostly absorb blue-violet light.

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    Why do leaves change color in autumn?

    Chlorophyll breaks down in cooler temperatures, revealing the yellow carotenoids and xanthophylls already present in the leaves.

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    What is the action spectrum?

    The action spectrum shows the efficiency of different wavelengths of light in driving photosynthesis. It resembles the absorption spectrum of chlorophyll a and b, indicating their role in light absorption.

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    What is cyclic photophosphorylation?

    A process where electrons cycle back to photosystem I, producing ATP but not NADPH.

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    What is the role of the stroma lamellae?

    The stroma lamellae are thylakoid membranes lacking PS II and NADP reductase, allowing for cyclic photophosphorylation.

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    What drives ATP synthesis in chloroplasts?

    ATP synthesis is linked to the proton gradient across the thylakoid membrane, similar to how it works in mitochondria.

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    Calvin Cycle Stages

    The Calvin cycle, a part of photosynthesis in plants, occurs in three stages: carboxylation, reduction, and regeneration.

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    Carboxylation in Calvin Cycle

    Carboxylation is the first stage of the Calvin cycle. It involves the addition of CO2 to RuBP (ribulose-1,5-bisphosphate), catalyzed by RuBisCO, forming an unstable 6-carbon compound that quickly breaks down into two 3-carbon compounds (3-PGA).

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    Reduction in Calvin Cycle

    In reduction, 3-PGA is converted to glyceraldehyde-3-phosphate (G3P), utilizing ATP and NADPH produced during light-dependent reactions. G3P is the final product of the Calvin cycle. It's a building block for glucose.

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    Regeneration in Calvin Cycle

    The regeneration phase of the Calvin cycle recycles 5 out of 6 G3P molecules to regenerate RuBP, the CO2 acceptor, ensuring the cycle's continuation. This step requires ATP.

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    RuBisCO: The Key Enzyme

    RuBisCO is a critical enzyme for photosynthesis. It catalyzes the carboxylation of RuBP in the Calvin cycle, incorporating CO2 into organic molecules.

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    ATP and NADPH in Calvin Cycle

    ATP is the energy currency, providing energy for the reactions in the Calvin cycle. NADPH is the electron donor and reducing power, required for the conversion of 3-PGA to G3P.

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    Glucose Production in Calvin Cycle

    Each turn of the Calvin cycle fixes one carbon atom. Six turns are needed to produce one glucose molecule (with six carbon atoms) from CO2.

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    Calvin Cycle Dependence on Light Reactions

    The Calvin cycle is dependent on the light-dependent reactions for the supply of ATP and NADPH. It cannot occur without these products.

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    Water Stress and Photosynthesis

    Water stress affects photosynthesis indirectly. It causes stomata to close, reducing CO2 uptake and wilting, decreasing leaf surface area and metabolic activity.

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    Dark Reactions (Calvin Cycle)

    This stage uses the energy carriers from light reactions to convert CO2 into glucose (sugar) for the plant's energy needs.

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    Photosystems I and II (PS I & PS II)

    These are protein complexes within the chloroplast that absorb light energy. PS I absorbs red light at 700 nm, while PS II absorbs red light at 680 nm.

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    Light-Independent Reactions (Calvin Cycle)

    The second stage of photosynthesis that occurs in the stroma of chloroplasts, using ATP and NADPH from the light-dependent reactions to convert CO2 into sugar.

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    ATP and NADPH use

    ATP and NADPH produced during the light-dependent reactions are used to power the biosynthetic phase of photosynthesis, specifically the Calvin cycle.

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    First CO2 Fixation Product

    The initial stable organic compound formed when carbon dioxide is incorporated into a plant during photosynthesis is a 3-carbon organic acid called 3-phosphoglyceric acid (PGA).

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    Why 'Dark Reaction' Misnomer?

    The term 'dark reaction' is a misnomer because while the Calvin cycle doesn't directly need light, it relies on the products of the light-dependent reactions (ATP and NADPH).

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    14C Experiments

    Melvin Calvin used radioactive carbon-14 (14C) to trace the path of carbon dioxide during photosynthesis in algae, revealing the Calvin cycle.

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    Energy for ATP Synthase

    The proton gradient across the thylakoid membrane provides enough energy to drive a conformational change in the CF1 particle of ATP synthase, leading to the production of ATP.

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    CO2 fixation rate

    The speed at which a plant converts carbon dioxide into sugars during photosynthesis.

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    Why is RuBisCO unique?

    RuBisCO has a dual function – it can bind to both CO2 and O2, making its activity dependent on the relative concentrations of these gases.

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    Light Harvesting Complex

    A network of pigments, mostly chlorophyll, that capture light energy and funnel it to the reaction center of a photosystem.

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    Reaction Center

    The site within a photosystem where light energy is converted into chemical energy. It contains a special chlorophyll a molecule that absorbs light and releases excited electrons.

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    Chloroplasts: Photosynthesis Site

    Chloroplasts are the organelles responsible for photosynthesis in plant cells. They have a membrane system for light reactions and a stroma for dark reactions.

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    C4 Plants vs. C3 Plants

    C4 plants have a different initial CO2 fixation pathway, concentrating CO2 in specific cells to minimize photorespiration. This makes them more efficient in hot environments.

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    What is the importance of Engelmann's experiment?

    Engelmann's experiment, using a prism and aerobic bacteria, helped to discover the action spectrum of photosynthesis. It revealed that certain wavelengths of light are more effective than others in driving the process.

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    Temperature optimum for photosynthesis

    The temperature range where photosynthesis occurs at its peak rate, typically between 30-40°C for most plants.

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    Identifying C4 plants

    Examine cross-sections of leaves under a microscope to observe the presence of Kranz anatomy—a ring of mesophyll cells encircling a bundle sheath cell.

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    Where Photosynthesis Occurs

    Photosynthesis primarily occurs in the chloroplasts of green leaves, but it can also occur in other green parts of plants like stems.

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    What is the first stable product formed when CO2 is fixed in photosynthesis?

    The first stable product is 3-phosphoglyceric acid (PGA), a 3-carbon organic acid.

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    How is the Calvin cycle dependent on light reactions?

    The Calvin cycle relies on ATP and NADPH, which are produced during the light-dependent reactions, to drive the synthesis of glucose from CO2.

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    What is the role of RuBisCO in photosynthesis?

    RuBisCO is the enzyme that catalyzes the fixation of CO2 into a 3-carbon compound in the Calvin cycle.

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    Why is the Calvin cycle also called the dark reaction?

    The Calvin cycle does not directly require light; it uses the products (ATP and NADPH) of the light reactions to function.

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    What is the purpose of photorespiration?

    Photorespiration is a wasteful process where RuBisCO binds to oxygen instead of carbon dioxide, leading to the release of CO2 and a loss of energy.

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    Study Notes

    Melvin Calvin

    • Born in Minnesota in 1911
    • Received a Ph.D. in Chemistry from the University of Minnesota
    • Served as Professor of Chemistry at the University of California, Berkeley
    • After World War II, used radioactivity to study plant reactions (specifically, the reactions in green plants that create sugar and other substances from raw materials)
    • Studied carbon dioxide reactions using C¹⁴-labeled carbon dioxide, water, and minerals in plants
    • Proposed that plants convert light energy to chemical energy by transferring electrons in organized pigment molecules and other substances
    • Mapped the pathway of carbon assimilation in photosynthesis
    • Awarded the Nobel Prize in 1961 for his work in photosynthesis
    • Research focuses on renewable resources for energy and materials, and basic solar energy research

    Photosynthesis in Higher Plants

    • All animals depend on plants for food
    • Green plants synthesize their own food through photosynthesis
    • Autotrophs (plants) produce food
    • Heterotrophs (animals) depend on plants for food
    • Plants use light energy to synthesize organic compounds
    • This process is crucial for life on Earth because it provides food and releases oxygen
    • Chlorophyll (a green pigment) is necessary for photosynthesis
    • Experiment: experiments show that chlorophyll, light, and CO2 are essential for photosynthesis to occur
    • Photosynthesis occurs only in the green parts of the leaves in the presence of light, experiments show that CO2 is needed for photosynthesis

    Early Experiments

    • Joseph Priestley (1733-1804) discovered oxygen in 1774
    • Experiments with burning candles, mice, and plants in closed spaces demonstrated the role of air in plant growth
    • Plants restore to the air what is removed through respiration from animals or through the combustion of candles
    • Jan Ingenhousz (1730-1799) showed that sunlight was essential to the process of purifying air that animals or candles foul
    • Observing aquatic plants and their reaction to sunlight, Ingenhousz found that oxygen is released only in sunlight (and only from the green part of plants)

    Other Experiments

    • Julius von Sachs (1854) demonstrated the production of glucose during plant growth- glucose is stored as starch
    • Chlorophyll is found in chloroplasts within plant cells
    • T.W Engelmann (1843–1909) identified the blue and red light regions of the spectrum from splitting light into spectral colors
    • identified bacteria accumulating in those areas; determined that absorption and action spectrum of chlorophyll a and b were similar

    Methods of Photosynthesis

    • The overall process of photosynthesis for oxygen-evolving organisms (using empirical equation) is CO₂ + H₂O → [CH₂O]+O₂ ([CH₂O] is a carbohydrate)
    • Plants convert light energy into chemical energy with processes that are dependent on the pigments present in a membrane
    • This pathway is called photosynthesis
    • Photosynthesis is divided into two processes; a light-dependent reaction (photochemical reactions) and a light-independent reaction (dark reactions or carbon reactions)
    • The process of photosynthesis occurs in the chloroplasts
    • There are several distinct photosystems (PS I and PS II) in the chloroplasts and they are connected by an electron transport system
    • Both ATP and NADP + H⁺ are produced during the light reactions, these products are utilized in biosynthetic reactions (that occurs within the stroma of chloroplasts) for carbohydrate synthesis—the dark reactions

    Factors Affecting Photosynthesis

    • Internal factors (number, size, age, and orientation of leaves, mesophyll cells, chloroplasts, internal CO₂ concentration, and amount of chlorophyll) and external factors (sunlight, CO₂ concentration, temperature, and water) affect photosynthesis
    • Limiting factors:
    • Blackman’s Law of Limiting Factors: if a chemical process is affected by multiple factors, the rate is dependent on the factor closest to its minimum value—meaning it can be changed, while the values of other factors remain unchanged. (Ex. low temperature, while other conditions are ideal, would limit the rate of photosynthesis)

    The Calvin Cycle

    • The Calvin cycle is a crucial part of photosynthesis in all plants

    • Contains three primary stages

      • Carboxylation: atmospheric CO₂ combines with RuBP (a 5-carbon acceptor molecule), forming two molecules of PGA (a 3-carbon molecule), with the help of the enzyme RuBisCo—a most abundant enzyme found commonly in plants
      • Reduction: The 3-PGA molecules are changed to triose sugars
      • Regeneration: RuBP is reformed from the 3-carbon molecules

    • The C₃ pathway: the original Calvin (and Benson-Calvin) pathway, where the first product of CO₂ fixation is a 3-carbon acid

    • The C₄ pathway: a pathway in which the first product of CO₂ fixation is a 4-carbon acid—the Calvin-cycle occurs in the bundle sheath cells of these plants

    Photorespiration

    • In C₃ plants, when CO₂ levels are low and O₂ levels are high, RuBisCO can add O₂ to RuBP, causing photorespiration—a competing process
    • Produces no usable energy (ATP and NADPH)
    • C₄ plants have a mechanism to concentrate CO₂ at the site of RuBisCo, minimizing photorespiration—this is a useful adaptation for these plants in high-temperature and low-CO₂ environments.

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    Photosynthesis in Higher Plants PDF

    Description

    Explore the groundbreaking work of Melvin Calvin, a pioneer in the study of photosynthesis. Dive into his research on how plants convert light energy into chemical energy, mapping the pathway of carbon assimilation. Discover the significance of his findings and their impact on renewable energy resources.

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