Photosynthesis Overview and Reactions (C2)
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Photosynthesis Overview and Reactions (C2)

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Questions and Answers

What are the main products generated by the light-dependent reactions of photosynthesis?

  • Glucose and O2
  • ATP and glucose
  • NADPH and O2
  • ATP and NADPH (correct)

    • In which part of the chloroplast do the light-independent reactions occur?

  • Inner membrane
  • Thylakoid membranes
  • Granum
  • Stroma (correct)

    • Which of the following statements is true regarding carbon fixation?

  • It requires ATP and does not involve NADPH
  • It occurs exclusively in the light-dependent reactions
  • It produces glucose directly from sunlight
  • It integrates CO2 into carbohydrate molecules (correct)

    • What role does chlorophyll play in photosynthesis?

    <p>It traps solar energy</p> Signup and view all the answers

    What is the primary function of the ATP produced during photosynthesis?

    <p>To power light-independent reactions</p> Signup and view all the answers

    Which process describes the conversion of solar energy into chemical energy during photosynthesis?

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

    Which of the following compounds is reduced during the light-dependent reactions?

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

    What are the reactants required for photosynthesis?

    <p>CO2, H2O, and light energy</p> Signup and view all the answers

    What is the primary function of ATP synthase?

    <p>To bond ADP and free phosphates to form ATP</p> Signup and view all the answers

    What is the end result of the light-dependent reactions during photosynthesis?

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

    Which step in the Calvin Cycle primarily utilizes CO2?

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

    How are G3P molecules related to glucose synthesis?

    <p>Two G3P molecules combine to form one glucose molecule</p> Signup and view all the answers

    What compound is reduced during the light reactions to form NADPH?

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

    What happens to the 5 G3P molecules produced after reduction?

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

    Which of the following statements is true about light-independent reactions?

    <p>They can take place without light but typically occur during the day.</p> Signup and view all the answers

    What is the role of rubisco in the Calvin Cycle?

    <p>To assist in the binding of CO2 to RuBP</p> Signup and view all the answers

    What is the primary role of photosystem II (PSII) in the light-dependent reactions?

    <p>Producing ATP through chemiosmosis</p> Signup and view all the answers

    What happens to the electron after it leaves the reaction center of PSII?

    <p>It joins an electron acceptor molecule</p> Signup and view all the answers

    What is the source of electrons that replaces the electron lost from PSII?

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

    In the context of photosynthesis, what is the purpose of the concentration gradient of H+ ions?

    <p>To produce ATP from ADP</p> Signup and view all the answers

    What is the function of ATP synthase in the light-dependent reactions?

    <p>To convert ADP and inorganic phosphate into ATP</p> Signup and view all the answers

    What effect does the movement of energized electrons through the electron transport system have on H+ ions?

    <p>It increases the concentration of H+ ions in the thylakoid space</p> Signup and view all the answers

    Which term describes the process that links the movement of H+ ions to ATP production?

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

    What is produced as a byproduct during the breakdown of water molecules in photosynthesis?

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

    Study Notes

    Photosynthesis Overview

    • Photosynthesis is the process by which plants, algae, and some bacteria use sunlight to convert carbon dioxide and water into glucose and oxygen.
    • The chemical equation for photosynthesis is: 6 CO2 + 6 H2O + light energy → 6 O2 + C6H12O6
    • Photosynthesis takes place in chloroplasts, which are organelles found in plant cells.
    • Photosynthesis consists of two sets of reactions: light-dependent reactions and light-independent reactions.

    Light-Dependent Reactions

    • Light-dependent reactions generate ATP and NADPH, which are used to power the light-independent reactions.
    • Light-dependent reactions occur in the thylakoid membranes of chloroplasts.
    • Light energy is absorbed by chlorophyll molecules in photosystems I and II (PSI and PSII).
    • This energy excites electrons in chlorophyll, causing them to move to electron acceptors.

    Photosystem II (PSII)

    • PSII uses a process called chemiosmosis to produce ATP.
    • When an electron leaves PSII, it creates an "electron hole".
    • Water is split to replace the electron in PSII, releasing H+ ions, electrons, and oxygen gas (O2).
    • The electrons from water move through an electron transport chain, losing energy along the way.
    • The lost energy is used to pump H+ ions into the thylakoid space, generating a concentration gradient.
    • H+ ions flow down the concentration gradient through ATP synthase, generating ATP from ADP and Pi.

    Photosystem I (PSI)

    • PSI also absorbs light energy, exciting electrons and passing them to an electron acceptor.
    • The electrons from PSII replace those lost from PSI.
    • The electrons from PSI are used to reduce NADP+ to NADPH.

    Light-Independent Reactions (Calvin Cycle)

    • The energy from ATP and NADPH is used in the light-independent reactions to synthesize glucose.
    • Light-independent reactions occur in the stroma of chloroplasts.
    • They consist of three main steps: carbon fixation, reduction, and regeneration of RuBP.

    Carbon Fixation

    • Carbon dioxide (CO2) combines with RuBP (ribulose bisphosphate) in the stroma, catalyzed by the enzyme rubisco.
    • This creates an unstable 6-carbon compound that immediately breaks down into two 3-carbon compounds called 3-PGA (3-phosphoglycerate).

    Reduction

    • 3-PGA is converted to G3P (glyceraldehyde-3-phosphate) by using energy from ATP and NADPH.
    • Two G3P molecules can combine to form one glucose molecule.

    Regeneration of RuBP

    • Five out of six G3P molecules are used to regenerate RuBP, requiring additional ATP.
    • The Calvin cycle must repeat to produce one full glucose molecule.

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    Description

    This quiz explores the process of photosynthesis, highlighting its significance in converting sunlight into energy for plants and other organisms. It delves into both light-dependent and light-independent reactions, emphasizing the roles of chloroplasts and photosystems. Test your knowledge on chemical equations and the mechanisms involved in this vital biological process.

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