Plant Biology: Oxygenic Photosynthesis
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Questions and Answers

What is the primary function of photosynthesis?

  • Conversion of chemical energy into light energy
  • Production of oxygen as a waste product
  • Conversion of light energy into chemical energy (correct)
  • Formation of carbon dioxide from glucose

    • NADP+ reductase is responsible for forming ATP during photosynthesis.

    False

    What are the two types of photosystems involved in photosynthesis?

    Photosystems I and II

    The process of ___ is involved in the generation of an H+ gradient during photosynthesis.

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

    Match the following components of photosynthesis with their roles:

    <p>Chloroplast = Site of photosynthesis ATP = Energy currency of the cell NADPH = Reducing power for biosynthetic reactions Herbicides = Compounds that can target photosynthesis</p> Signup and view all the answers

    What percentage of the Earth's atmosphere is composed of oxygen?

    <p>20%</p> Signup and view all the answers

    The oxygen level in the atmosphere has always been above 20%.

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

    What process is responsible for generating oxygen in the atmosphere?

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

    The percentage of oxygen in the atmosphere is approximately _____ percent.

    <p>20</p> Signup and view all the answers

    Match the following terms with their descriptions:

    <p>Oxygen = Essential for respiration in animals Photosynthesis = Process by which plants produce oxygen Atmosphere = Layer of gases surrounding the Earth Carbon Dioxide = Gas consumed by plants during photosynthesis</p> Signup and view all the answers

    At what point in time did oxygen levels begin to rise significantly in the atmosphere?

    <p>Around 2 billion years ago</p> Signup and view all the answers

    Photosynthesis has no effect on the amount of oxygen in the atmosphere.

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

    What role does photosynthesis play in maintaining atmospheric oxygen levels?

    <p>It produces oxygen as a byproduct.</p> Signup and view all the answers

    What is primarily affected by high light and low temperature in Photosystem II?

    <p>Rate of electron transport</p> Signup and view all the answers

    Photosystem I contributes to the production of NADP+.

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

    What does the term 'non-photochemical quenching' refer to in the context of excess light?

    <p>The process that dissipates excess energy as heat to protect the plant from damage.</p> Signup and view all the answers

    In the thylakoid lumen, the reaction involving water produces oxygen and _____.

    <p>protons (H+)</p> Signup and view all the answers

    Match the following components of the photosynthetic process with their roles:

    <p>P680 = Primary electron donor in Photosystem II Cyt b6f = Connects Photosystem II and I P700 = Primary electron donor in Photosystem I NADP+ = Final electron acceptor</p> Signup and view all the answers

    What is generated as a byproduct of splitting water in photosynthesis?

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

    Photosystem I primarily participates in cyclic photosynthesis.

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

    What is the main role of Cyt b6f in photosynthesis?

    <p>It facilitates the transfer of electrons between photosystem II and photosystem I.</p> Signup and view all the answers

    The process of ______ is primarily affected by the herbicide atrazine.

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

    Match the following components of the photosynthesis process with their functions:

    <p>NADP+ = Electron carrier P680 = Reaction center of Photosystem II PC = Plastocyanin APX = Decomposes H2O2</p> Signup and view all the answers

    Which element is generated during the process of cyclic photosynthesis?

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

    Excess light leads to a mechanism referred to as the water-water cycle.

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

    What role does ascorbate play in the photosynthetic process?

    <p>It acts as an antioxidant.</p> Signup and view all the answers

    Chlorophyll b primarily absorbs light at the wavelength of 680 nm.

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

    What is the role of NADP+ in photosynthesis?

    <p>It serves as an electron carrier and reduces to NADPH.</p> Signup and view all the answers

    The process of _______ creates an electrochemical gradient during photosynthesis.

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

    Match the following pigments with their characteristics:

    <p>Chlorophyll a = Amax ~ 670 nm Chlorophyll b = Amax ~ 650 nm Accessory pigments = Enhance light harvesting capabilities RC Chlorophyll a = Amax ~ 680 nm (PSII)</p> Signup and view all the answers

    During the light reactions, which of the following occurs first?

    <p>Primary charge separation</p> Signup and view all the answers

    The Calvin cycle occurs during the light-dependent reactions of photosynthesis.

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

    What is the byproduct of water oxidation during photosynthesis?

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

    The primary electron transport chain in photosynthesis is located in the _______.

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

    Which of the following terms refers specifically to the absorption of specific wavelengths of light by chlorophyll?

    <p>Relative absorbance</p> Signup and view all the answers

    What is produced as a byproduct of photosynthesis?

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

    Cyclic photosynthesis involves two distinct light harvesting systems.

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

    In photosynthesis, which molecule is ultimately reduced to form NADPH?

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

    Photosynthesis converts light to ______ energy.

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

    Match the following processes involved in photosynthesis with their functions:

    <p>Chemiosmosis = ATP generation using a proton gradient Light-induced electron transfer = Harvester of light energy for photosynthesis Photosystem I = Involved in cyclic photophosphorylation Photosystem II = Splits water molecules to release oxygen</p> Signup and view all the answers

    Which of the following is NOT a product of aerobic respiration?

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

    Photosynthesis and aerobic respiration produce the same gases.

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

    What is the proton gradient used for in photosynthesis?

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

    Study Notes

    Oxygenic Photosynthesis

    • Oxygenic photosynthesis converts light energy into chemical energy and reducing power.
    • Chemiosmosis is used to create ATP.
    • NADP+ reductase converts NADP+ to NADPH.

    Photosynthesis Summary

    • Photosynthesis converts light energy into chemical energy and reducing power.
    • Chemiosmosis generates ATP.
    • NADP+ reductase forms NADPH.
    • Smith, & Smith, A. M. (Alison M. 2010). Plant biology. Garland Science. ISBN: 9780815340256
    • 3 copies available in the Main Library, General Shelving; 580 P 713.

    Photosynthesis Learning Objectives

    • Understand photosynthetic use of different wavelengths of light.
    • Know the structure of chloroplasts.
    • Understand the structure, function and molecular mechanism of photosystems I and II.
    • Förster resonant energy transfer.
    • Convert light into chemical energy.
    • Generate H+ gradients.
    • Understand electron transport.
    • Recognize how herbicides target photosynthesis.
    • Understand how chloroplasts adjust to environmental changes.

    What has Photosynthesis Ever Done for Us?

    • Graph showing oxygen levels in the atmosphere throughout time.
    • Photosynthesis's role in creating the Earth's oxygen-rich atmosphere and supporting life.

    Cyanobacteria and Chloroplasts

    • Cyanobacteria are photosynthetic organisms.
    • Chloroplasts have similar structural features to cyanobacteria, suggesting a common ancestry.
    • Images comparing cyanobacteria and chloroplast structure.

    Chloroplast Structure

    • The chloroplast contains stroma, thylakoid (inner and outer bilayer membranes), grana, and lumen.

    Thylakoid Structure

    • The thylakoid membrane contains photosystems II and I, cytochrome b6f complex, and ATP synthase.

    The Structure of a Thylakoid

    • The diagram shows the movement of electrons and protons through photosystems, to generate ATP and NADPH used in the Calvin cycle.

    Why are Chloroplasts Green?

    • Chlorophyll absorbs light most strongly in the blue and red regions of the spectrum, reflecting green light.

    Photosynthetically Active Radiation (PAR)

    • Graph demonstrating different wavelengths of light absorbed by different types of chlorophyll.

    Photosynthesis Summary (Alternative)

    • Conversion of light energy into chemical energy and reducing power.
    • Chemiosmosis produces ATP.
    • NADP+ reductase forms NADPH.

    Photosynthesis Summary (Diagram)

    • The diagram illustrates the steps in photosynthesis, including light excitation, energy transfer, charge separation, electron transfer, and ATP synthesis.

    Chlorophyll

    • Chlorophyll a and b are key pigment molecules in photosynthesis, with slightly different absorption spectra.
    • Chemistry diagrams show the chemical structure of chlorophyll.

    Structure of a Photosystem

    • Diagram showing the light harvesting complex surrounding the core complex of chlorophyll a molecules that drive the electron transfer.

    Light Harvesting Complex

    • Accessory pigments enhance light harvesting efficiency.
    • Diagram shows how accessory pigments capture light and transfer the energy to a central chlorophyll.

    Chlorophyll Energy Transfer

    • Förster resonance energy transfer, transferring energy from one chlorophyll molecule to another.

    Photosystems, ETC, and ATP Synthesis

    • Diagram illustrating the electron transport chain (ETC) and ATP synthesis in the thylakoid membrane.

    The Z-Scheme

    • Diagram outlines the Z-scheme, the overall process of light-driven electron transport.

    Photosystems, ETC, and ATP Synthesis (Alternative)

    • Diagram illustrating the ETC, showing electron flow and proton gradient across the thylakoid membrane, driving ATP synthesis.

    Photosystem II-Oxygen Producing

    • Diagram shows the components of photosystem II and the step-by-step process that split water molecules to release electrons and oxygen.

    Photosystem I - NADPH Producing

    • Diagram illustrates the components of photosystem I and the transfer of electrons for NADPH production.

    Photosynthesis and the Environment

    • Factors like day/night cycles, cloud cover, canopy cover, and high exposure influence photosynthesis rates.

    Too much Light - PSII

    • Explanation of rate limiting steps in photosynthesis.

    Too much Light - Non-photochemical Quenching

    • Explanation of the mechanism of non-photochemical quenching, and how the plant protects itself from excessive light.

    Too much Light- PSI

    • Explanation of rate limiting steps in photosynthesis when photosystem I is impacted by too much light.

    Too Much Light - The Water-Water Cycle

    • Diagram illustrating the mechanism of cyclic electron transport, and roles of different enzymes in response to excessive light.

    Herbicides

    • Effects of herbicides on photosynthetic processes.

    ###Herbicide Deactivation

    • Diagram showing how herbicides disrupt electron transport in photosynthesis.

    Cyclic Photosynthesis

    • Cyclic photosynthesis pathway in plants.
    • Diagram illustrates the cyclic electron pathway without water being split.

    Cyclic Photosynthesis (Alternative)

    • Mechanism of cyclic photosynthesis used by purple and green bacteria, and under certain conditions in plants.

    Comparison with Aerobic Respiration

    • Photosynthesis vs. aerobic respiration, highlighting the contrasting input/output requirements.

    Summary

    • Photosynthesis converts light to chemical energy.
    • ATP is formed via chemiosmosis during electron transfer.
    • Two linked photosystems are crucial for efficient electron transfer from water to NADPH.

    Further Reading

    • Additional topics to explore regarding photosynthesis, including why there's only one electron path in PSII, cyclic photosynthesis, effects of blue light absorption, and differences in plant compensation points between species.

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    Photosynthesis - Hemsley - 2024 PDF

    Description

    This quiz covers key concepts in oxygenic photosynthesis, including the conversion of light energy into chemical energy, the role of chemiosmosis in ATP generation, and the function of NADP+ reductase. Explore the structure of chloroplasts and the mechanisms of photosystems I and II. Test your understanding of photosynthetic processes and their applications.

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