Photosynthesis and Photorespiration Quiz
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Questions and Answers

What occurs during photorespiration that makes it considered wasteful?

  • It produces more energy than required.
  • It fixes more carbon than photosynthesis.
  • It consumes ATP without producing any sugar. (correct)
  • It enhances the rate of photosynthesis.
  • Which compound is primarily lost as a result of photorespiration?

  • Oxygen
  • Carbon dioxide (correct)
  • Glycine
  • Glucose
  • What is the role of rubisco in the process when photorespiration occurs?

  • It binds to O2 instead of CO2. (correct)
  • It catalyzes the conversion of glycolate to glycine.
  • It fixes CO2 to produce glucose.
  • It increases RuBP availability.
  • What is Kranz anatomy characteristic of?

    <p>C4 plants (C)</p> Signup and view all the answers

    Which mechanisms have developed in plants to minimize photorespiration?

    <p>C4 and CAM photosynthesis (D)</p> Signup and view all the answers

    How does photorespiration affect photosynthetic efficiency?

    <p>It diverts resources away from the Calvin cycle. (D)</p> Signup and view all the answers

    Which plant type is primarily associated with tropical regions due to adaptations to avoid photorespiration?

    <p>C4 plants (A)</p> Signup and view all the answers

    What is a consequence of photorespiration on plant growth?

    <p>It leads to reduced plant growth due to energy diversion. (B)</p> Signup and view all the answers

    What characteristic of chlorophyll contributes to the green color of most plants?

    <p>Chlorophyll reflects blue and red wavelengths. (B)</p> Signup and view all the answers

    Which type of radiation has the highest energy according to its wavelength?

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

    What is the primary function of carotenoids in photosynthesis?

    <p>To absorb wavelengths mainly in the blue-violet region. (D)</p> Signup and view all the answers

    What is the primary function of the energy carried by electrons during photosynthesis?

    <p>To create a potential energy store by moving hydrogen ions (C)</p> Signup and view all the answers

    What do the absorption and action spectra of photosynthetic pigments indicate?

    <p>Both spectra have peaks at similar wavelengths. (C)</p> Signup and view all the answers

    Which molecule is directly produced when water is split during photosynthesis?

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

    How does photon energy correlate with the wavelength of electromagnetic radiation?

    <p>Shorter wavelengths have higher energy photons. (D)</p> Signup and view all the answers

    What is the significance of chloroplasts being arranged at right angles to light sources?

    <p>To maximize the absorption of light. (C)</p> Signup and view all the answers

    What role does Rubisco play in the light-independent reactions of photosynthesis?

    <p>It fixes carbon dioxide into 3-carbon molecules (C)</p> Signup and view all the answers

    Which statement accurately describes the behavior of light as electromagnetic radiation?

    <p>Light can behave as both waves and particles under different conditions. (A)</p> Signup and view all the answers

    In the process of making sugars during photosynthesis, what happens to most of the 3C molecules (G3P) produced?

    <p>They are recycled to regenerate RuBP. (D)</p> Signup and view all the answers

    What defines an absorption spectrum in the context of photosynthetic pigments?

    <p>It indicates specific wavelengths absorbed by a pigment. (B)</p> Signup and view all the answers

    What is the main waste product generated during the light-independent stage of photosynthesis?

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

    Which factor is NOT mentioned as affecting the rate of photosynthesis?

    <p>Soil moisture levels (A)</p> Signup and view all the answers

    What happens to the energy from ATP in the light-independent reactions?

    <p>It phosphorylates 3C molecules to increase energy. (D)</p> Signup and view all the answers

    Which chloroplast pigment is primarily responsible for capturing light energy during photosynthesis?

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

    What is the primary function of the stomata in the lower epidermis of a leaf?

    <p>Regulate gas exchange (C)</p> Signup and view all the answers

    What is referred to as the compensation point in photosynthesis?

    <p>The point where carbon dioxide uptake equals oxygen release (C)</p> Signup and view all the answers

    Which of the following statements correctly distinguishes between absorption and action spectra?

    <p>Absorption spectra indicate colors absorbed; action spectra indicate colors used in photosynthesis. (D)</p> Signup and view all the answers

    What structure in the chloroplast allows for the primary and accessory pigments to compete for light absorption?

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

    Which type of mesophyll cell is mainly responsible for photosynthesis due to its high chloroplast content?

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

    What is the role of carotenoids in photosynthesis, aside from light absorption?

    <p>They act as a protective antioxidant. (B)</p> Signup and view all the answers

    How does the structure of the upper epidermis contribute to its primary function?

    <p>It's covered with a waxy cuticle for protection and to prevent water loss. (A)</p> Signup and view all the answers

    Which of the following best describes the role of guard cells?

    <p>They regulate the opening and closing of stomata. (D)</p> Signup and view all the answers

    What is the effect of increasing light intensity on the rate of photosynthesis?

    <p>It increases the rate depending on the distance from the light source. (C)</p> Signup and view all the answers

    Which component must be altered in the water to investigate the limiting factor of carbon dioxide concentration in photosynthesis?

    <p>Amount of NaHCO3 (A)</p> Signup and view all the answers

    What differentiates C3 plants from C4 plants in terms of carbon fixation?

    <p>C3 plants form glucose directly, whereas C4 plants fix carbon into a four-carbon compound initially. (B)</p> Signup and view all the answers

    How do C4 plants avoid photorespiration?

    <p>By separating carbon fixation and the Calvin cycle in different cell types. (D)</p> Signup and view all the answers

    What is a key characteristic of CAM plants in their photosynthesis process?

    <p>They fix carbon dioxide at night and store it for use during the day. (C)</p> Signup and view all the answers

    What is the primary stable compound produced by C3 plants during photosynthesis?

    <p>Glyceraldehyde 3-phosphate (D)</p> Signup and view all the answers

    What is indicated by the relationship 'intensity ∝ 1/d^2' in regards to light intensity?

    <p>As distance increases, light intensity decreases quadratically. (A)</p> Signup and view all the answers

    Why is it important to keep control variables constant when investigating photosynthesis?

    <p>To isolate the effects of the limiting factors being tested. (D)</p> Signup and view all the answers

    What is the primary function of the bundle sheath cells in C4 plants?

    <p>Fixing atmospheric CO2 (B)</p> Signup and view all the answers

    Which of the following statements correctly describes the chloroplasts in mesophyll cells?

    <p>They have grana and are involved in light-dependent reactions (C)</p> Signup and view all the answers

    What is the role of PEP carboxylase in the C4 pathway?

    <p>To fix atmospheric CO2 into a 4-carbon compound (B)</p> Signup and view all the answers

    Which statement accurately describes the starch content between mesophyll and bundle sheath cells?

    <p>Bundle sheath cells are rich in starch while mesophyll cells contain minimal amounts (C)</p> Signup and view all the answers

    What distinguishes the light-dependent reactions in mesophyll cells from those in bundle sheath cells?

    <p>Bundle sheath cells have no light-dependent reactions at all (A)</p> Signup and view all the answers

    What is transported through plasmodesmata between the mesophyll and bundle sheath cells?

    <p>Metabolites including malate and pyruvate (A)</p> Signup and view all the answers

    Which of the following best describes the Calvin cycle's location in C4 plants?

    <p>It takes place in the bundle-sheath cells (D)</p> Signup and view all the answers

    What happens to pyruvate after it is produced in the bundle sheath cells?

    <p>It is converted back to PEP in mesophyll cells (D)</p> Signup and view all the answers

    Flashcards

    Cutin

    A waxy, waterproof layer covering the external walls of the upper and lower epidermis of a leaf, protecting it from water loss and infection.

    Stomata

    Tiny pores on the lower epidermis of a leaf that allow for gas exchange (CO2 in, O2 out).

    Guard cells

    Specialized cells surrounding each stoma that control its opening and closing, regulating gas exchange.

    Palisade mesophyll

    Column-shaped cells in the mesophyll layer of a leaf, packed with chloroplasts for maximum photosynthesis.

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    Spongy mesophyll

    Irregularly shaped cells in the mesophyll layer, creating air spaces for gas diffusion and containing fewer chloroplasts than palisade cells.

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    Chlorophyll

    Green pigments that absorb light energy for photosynthesis.

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    Accessory pigments

    Pigments that capture light energy and transfer it to chlorophyll, expanding the range of light used in photosynthesis.

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    Absorption spectrum

    The spectrum of wavelengths of light absorbed by a pigment.

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    Visible Spectrum

    The portion of the electromagnetic spectrum that our eyes can detect, ranging from approximately 400 to 700 nanometers in wavelength.

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    Photons

    Packets of energy that make up electromagnetic radiation.

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    Photosynthetic Pigments

    Pigments that absorb specific wavelengths of light, allowing plants to capture energy for photosynthesis.

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    Carotenoids

    Pigments that absorb mainly blue-violet light and transfer that energy to chlorophyll, expanding the range of light used for photosynthesis.

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    Action Spectrum

    A graph illustrating the rate of photosynthesis at different wavelengths of light.

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    Photosynthesis

    The process where light energy is converted into chemical energy in the form of glucose, using carbon dioxide and water as reactants.

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    Light-dependent stage

    The first stage of photosynthesis, where light energy is captured and used to split water and produce ATP and NADPH.

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    Light-independent stage

    The second stage of photosynthesis, where carbon dioxide is fixed and converted into glucose using energy from ATP and NADPH.

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    Limiting factor

    A factor that limits the rate of photosynthesis when its amount is insufficient, even if other factors are optimal.

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    Light intensity

    The intensity of light that determines the rate of photosynthesis.

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    Wavelength of light

    Specific wavelengths of light that are most effective in driving photosynthesis.

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    Carbon dioxide concentration

    The amount of carbon dioxide in the air that determines the rate of photosynthesis.

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    Temperature

    The temperature that determines the rate of photosynthesis, as enzymes involved in the process have optimal temperatures.

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    C4 Plants

    Photosynthesis in these plants begins with fixing carbon dioxide into a four-carbon compound, hence the name. They are more efficient in hot, dry climates.

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    C3 Plants

    Plants that directly fix carbon dioxide into a three-carbon compound, glyceraldehyde 3-phosphate, during photosynthesis.

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    Photorespiration

    A process where plants use oxygen instead of carbon dioxide to fix carbon, resulting in a net loss of energy. It occurs when stomata are closed to conserve water, limiting CO2 uptake and increasing O2.

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    Two types of chloroplasts in a C4 leaf

    C4 plants have specialized cells called bundle sheath cells that contain chloroplasts where the Calvin cycle occurs. These chloroplasts are structurally different from those in mesophyll cells.

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    Internal leaf structure of C4 plants

    C4 plants have a special structure within their leaves where carbon fixation occurs, called the kranz anatomy, which includes mesophyll cells and bundle sheath cells with different chloroplasts.

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    CAM Plants

    These plants open their stomata at night to take in carbon dioxide, store it as an acid, and then release it during the day for photosynthesis when it's hot and dry, minimizing water loss.

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    Limiting factors in Photosynthesis

    These occur when a factor limits the rate of photosynthesis, even if other factors are optimal. For example, a lack of light will limit photosynthesis, even if there's plenty of water and carbon dioxide.

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    Carbon loss in photorespiration

    The loss of carbon dioxide during photorespiration, which is unproductive as it doesn't contribute to sugar production.

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    Energy expenditure in photorespiration

    The energy used in photorespiration is not used for growth or other essential processes, making it a wasteful process.

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    Reduced photosynthetic efficiency

    When photorespiration is active, it competes with photosynthesis for the same resources, reducing the overall efficiency of the process.

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    Kranz anatomy

    A type of leaf anatomy found in C4 plants, characterized by two concentric layers of cells: mesophyll cells and bundle sheath cells.

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    C4 photosynthesis

    A type of photosynthesis where carbon dioxide is first incorporated into a 4-carbon compound before entering the Calvin cycle, reducing photorespiration.

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    Mesophyll cells

    The outer layer of cells in Kranz anatomy, where the initial fixation of carbon dioxide occurs in C4 plants.

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    Spatial Separation in C4 Photosynthesis

    In C4 plants, the light-dependent reactions occur in the mesophyll cells, while the Calvin cycle occurs in the bundle-sheath cells. This spatial separation allows for more efficient carbon fixation.

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    PEP Carboxylase in C4 Plants

    In C4 plants, the enzyme PEP carboxylase is used to initially fix carbon dioxide into a 4-carbon organic acid called oxaloacetate. This enzyme does not bind with oxygen, preventing photorespiration.

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    Malate Transport in C4 Plants

    Oxaloacetate, a 4-carbon molecule produced in the mesophyll cells, is converted into malate. Malate then moves into the bundle-sheath cells, where it releases carbon dioxide and pyruvate.

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    Dimorphic Chloroplasts in C4 Plants

    C4 plants have specialized chloroplasts in both mesophyll and bundle sheath cells, each with different functions. Mesophyll chloroplasts have large grana for efficient light-dependent reactions, while bundle sheath chloroplasts lack grana and have high levels of rubisco for carbon fixation.

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    Hatch-Slack Pathway

    The Hatch-Slack pathway is the specific metabolic pathway utilized by C4 plants for carbon fixation. In this pathway, CO2 is initially fixed into a 4-carbon compound, facilitating efficient carbon fixation.

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    Plasmodesmata Connection in C4 Plants

    The movement of metabolites between mesophyll and bundle sheath cells is facilitated by plasmodesmata, creating continuous connections and enabling molecule exchange for efficient photosynthesis.

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    Kranz Anatomy in C4 Plants

    C4 plants are characterized by Kranz anatomy, where the bundle sheath cells are large and closely surrounded by mesophyll cells. This structural arrangement optimizes the flow of metabolites and ensures efficient photosynthesis.

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    Specialization of Chloroplasts in C4 Plants

    While mesophyll chloroplasts have high rates of light-dependent reactions generating abundant ATP, NADPH, and oxygen, bundle sheath chloroplasts focus on carbon fixation. This specialization improves the overall efficiency of photosynthesis.

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    Study Notes

    Introduction to Photosynthesis

    • Photosynthesis is the process by which plants and some other organisms convert light energy into chemical energy in the form of sugars.
    • This chemical energy is then used to fuel the organisms' metabolic processes.

    Autotrophic Nutrition

    • Autotrophic nutrition is the synthesis of organic compounds from inorganic sources.
    • Plants use photosynthesis as a source of energy for autotrophic nutrition.
    • Chemosynthesis is another method of autotrophic nutrition, where organisms use the oxidation of inorganic molecules as an energy source.

    Photosynthesis

    • Photosynthesis is the process plants and some algae utilize to convert light energy into chemical energy.
    • This process involves two main stages: light-dependent reactions and light-independent reactions (Calvin cycle).

    Light-Dependent Reactions

    • These reactions occur in the thylakoid membranes of chloroplasts.
    • Light is absorbed by chlorophyll and other pigments, converting light energy into chemical energy.
    • Water is split, releasing oxygen as a byproduct (photolysis of water).
    • ATP and NADPH are produced, carrying the chemical energy for the next stage.
    • Cyclic and non-cyclic photophosphorylation are distinct pathways within these reactions, which generate ATP.

    Light-Independent Reactions (Calvin Cycle)

    • These reactions take place in the stroma of chloroplasts.
    • Carbon dioxide from the atmosphere is fixed (combined) with RuBP (ribulose bisphosphate), a 5-carbon molecule.
    • An enzyme called RuBisCO catalyzes this reaction, creating a 6-carbon molecule that quickly splits into two 3-carbon molecules (3-PGA).
    • ATP and NADPH from the light-dependent reactions provide energy and electrons to convert 3-PGA into G3P (glyceraldehyde-3-phosphate); a 3-carbon sugar.
    • Some G3P molecules are used to form glucose and other organic molecules.
    • RuBP is regenerated in the cycle to continue the process.

    Factors Affecting Photosynthesis

    • Light intensity: Higher intensity generally increases the rate of photosynthesis until a saturation point is reached.
    • Wavelength of light: Different wavelengths of light are absorbed differently by pigments, primarily chlorophyll.
    • Carbon dioxide concentration: Higher concentrations generally increase photosynthetic rate, though there is a saturation point.
    • Temperature: Optimum temperatures increase photosynthesis; high or low temperatures negatively affect the rate of photosynthesis.

    C3, C4, and CAM Plants

    • C3 plants use the Calvin cycle, whereas C4 plants have a different pathway (Hatch-Slack cycle) that minimizes photorespiration in hot, dry conditions.
    • CAM plants also have a specialized pathway to conserve water.

    Practical Aspects of Photosynthesis

    • Various techniques can be used to study the rate of photosynthesis, including chromatography and redox indicators.
    • Investigating the rate of photosynthesis can be done through experiments that involve aquatic plants (e.g., Elodea or Cabomba) measuring oxygen production as a measure of photosynthesis rate under different conditions.

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    Description

    This quiz explores the intricacies of photosynthesis and the process of photorespiration in plants. It includes questions about key compounds, mechanisms to minimize photorespiration, and the physiological impacts on plant growth. Test your knowledge on the chlorophyll characteristics and pigment functions involved in these processes.

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