Photosynthesis Overview: Light Reactions and Calvin Cycle
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Questions and Answers

Which of these statements best describes the relationship between the light reactions and the Calvin cycle?

  • The Calvin cycle provides the light reactions with ATP and NADPH, which are then used to split water.
  • The light reactions provide the Calvin cycle with ATP and NADPH, which are then used to fix carbon dioxide. (correct)
  • The light reactions use carbon dioxide to generate glucose, which is then used by the Calvin cycle to produce ATP and NADPH.
  • The Calvin cycle produces oxygen as a byproduct, which is then used by the light reactions to power electron transport.

    • Which of the following is NOT a component of the light-dependent reactions of photosynthesis?

  • Rubisco (correct)
  • Photosystem II
  • Photosystem I
  • Cytochrome b6-f complex

    • What is the primary role of the light reactions in photosynthesis?

  • To convert light energy into chemical energy in the form of ATP and NADPH. (correct)
  • To fix carbon dioxide into glucose.
  • To release oxygen as a byproduct.
  • To produce water molecules.

    • Which of these statements accurately describes the role of water in the light reactions of photosynthesis?

    <p>Water is split to provide electrons for the electron transport chain and releases oxygen as a byproduct.</p> Signup and view all the answers

    Which of these organisms are considered photoautotrophs?

    <p>Plants that obtain energy from sunlight</p> Signup and view all the answers

    Which of these is NOT a synonym for the Calvin Cycle?

    <p>Light Reactions</p> Signup and view all the answers

    What is the primary source of chemical energy for a cell?

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

    What is the primary source of reducing power for a cell?

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

    What type of chlorophyll is found in prokaryotes?

    <p>Only chlorophyll a</p> Signup and view all the answers

    What is the ultimate source of electrons in green and purple sulfur bacteria?

    <p>H2S</p> Signup and view all the answers

    What is the byproduct of photosynthesis in green and purple sulfur bacteria?

    <p>Elemental S</p> Signup and view all the answers

    What is the structural basis of chlorophyll?

    <p>Tetrapyrrole ring of porphyrins</p> Signup and view all the answers

    What is the role of most pigments in a chloroplast?

    <p>Light absorption</p> Signup and view all the answers

    What is the term for organisms that contain bacteriochlorophyll?

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

    What is the name of the process that converts light energy into chemical energy?

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

    Which of the following is NOT a characteristic of photoautotrophs?

    <p>They obtain their energy from consuming other organisms.</p> Signup and view all the answers

    Where in the chloroplast do the light-dependent reactions of photosynthesis take place?

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

    What is the main product of the Calvin cycle?

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

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

    <p>They provide energy and reducing power for carbon fixation.</p> Signup and view all the answers

    What is the primary source of electrons for the light-dependent reactions of photosynthesis?

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

    How are the light-dependent reactions of photosynthesis similar to the electron transport chain in cellular respiration?

    <p>They both utilize a proton gradient to generate ATP.</p> Signup and view all the answers

    What are the two photosystems involved in the light-dependent reactions, and what are their functions?

    <p>Photosystem I - reduces NADP+ to NADPH; Photosystem II - oxidizes water to produce oxygen.</p> Signup and view all the answers

    Study Notes

    Photosynthesis Overview

    • Photosynthesis involves light-dependent (light reactions) and light-independent reactions (Calvin Cycle).
    • Light reactions occur in thylakoid membranes; Calvin Cycle takes place in the stroma.
    • Light energy drives the production of ATP and NADPH, which are utilized for synthesizing organic compounds (e.g., carbohydrates).

    Phase 1: Light Reactions

    • Light reactions categorized as light reactions (Photosystem I & II) and are crucial for energy production.
    • Photosystem II splits water, producing oxygen through an oxygen-evolving complex and transferring electrons through several carriers: Phaeophytin, Plastoquinone, and Cytochrome b6-f complex.
    • Electron transport in Photosystem I leads to the reduction of NADP+ to NADPH, involving ferredoxin and cyclic electron transport.
    • Photosystems are membrane-bound protein complexes, essential for harnessing solar energy.

    Photosystem Functions

    • Photosystem I is excited by certain wavelengths of light and drives the reduction of NADP+.
    • The connection between Photosystems I and II is crucial for the electron transport chain, facilitating ATP production.
    • Thylakoid membranes contain chlorophyll and other pigments to capture light energy.

    Light vs. Dark Reactions

    • Light reactions convert light energy to chemical energy, yielding ATP (energy source) and NADPH (reducing power).
    • Dark reactions utilize ATP and NADPH generated from the light reactions to fix CO2 into carbohydrates.

    Chlorophyll

    • Primary photosynthetic pigment; two main types: chlorophyll a (dominant in eukaryotes) and chlorophyll b (found in plants and algae).
    • Prokaryotes (e.g., cyanobacteria) contain only chlorophyll a.
    • Bacteriochlorophyll, present in some photosynthetic bacteria, replaces chlorophyll and does not produce oxygen during photosynthesis.

    Photosynthetic Bacteria

    • Green and purple sulfur bacteria contain bacteriochlorophylls and utilize H2S instead of water, producing elemental sulfur instead of oxygen.
    • These organisms are anaerobic and possess a single photosystem.

    Pigments and Reaction Centers

    • Not all chlorophyll molecules are involved in energy conversion; some aid solely in light absorption.
    • Chlorophyll structures resemble the heme group found in myoglobin and hemoglobin, differing primarily by the presence of magnesium instead of iron.

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    Description

    This quiz covers the basics of photosynthesis, including the light reactions and the Calvin cycle. Test your understanding of how light energy is converted into organic compounds.

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