Photosynthesis Mechanisms and Processes Quiz
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Questions and Answers

Which process involves only photosystem I (PSI) and recycles electrons?

  • Chemiosmosis
  • Photolysis
  • Non-cyclic photophosphorylation
  • Cyclic photophosphorylation (correct)

    • During photophosphorylation, what replaces the lost electrons in photosystem II?

  • Electrons from photosystem I
  • Electrons from NADPH
  • Electrons produced by the splitting of water (correct)
  • Electrons from the electron transport chain

    • What does cyclic photophosphorylation primarily produce?

  • NADPH and O2
  • O2 only
  • ATP only (correct)
  • ATP and NADPH

    • What enzymes are involved in the transfer of electrons to NADP+ during photophosphorylation?

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

    Which mechanism directly produces ATP during photophosphorylation?

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

    What is the primary product synthesized from glyceraldehyde 3-phosphate (GALP) in the Calvin cycle?

    <p>Simple sugars</p> Signup and view all the answers

    Which factor can cause a decrease in the rate of photosynthesis if it exceeds an optimum level?

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

    In the context of photosynthesis, what role does DCPIP play in the Hill Reaction experiment?

    <p>It serves as an electron acceptor.</p> Signup and view all the answers

    Which substance is produced when glycerate 3-phosphate (GP) is utilized during the Calvin cycle?

    <p>Nucleic acids</p> Signup and view all the answers

    What is the expected effect of increased light intensity on the Calvin cycle?

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

    Where does the Calvin cycle take place within the chloroplast?

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

    What is the primary product formed during the reduction phase of the Calvin cycle?

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

    What role does RuBisCO play in the Calvin cycle?

    <p>It combines CO₂ with RuBP</p> Signup and view all the answers

    What happens to most of the glyceraldehyde 3-phosphate (GALP) molecules produced in the Calvin cycle?

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

    Which compounds provide energy and electrons during the reduction phase of the Calvin cycle?

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

    What is the main function of the light-dependent reaction in photosynthesis?

    <p>To absorb sunlight and convert it to chemical energy</p> Signup and view all the answers

    Which reaction occurs during photolysis in photosynthesis?

    <p>H₂O → 2H⁺ + O₂</p> Signup and view all the answers

    Where do the light-independent reactions occur in the chloroplast?

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

    What is the role of ATP in the light-independent reactions?

    <p>To supply energy for synthesizing glucose</p> Signup and view all the answers

    What is generated during cyclic photophosphorylation?

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

    What process helps to create a proton gradient during the light-dependent reactions?

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

    What primarily excites the electrons in the chlorophyll during the light-dependent reaction?

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

    What is formed when NADP is reduced in photosynthesis?

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

    Which of the following statements is true about the products of the light-dependent reaction?

    <p>Reduced NADP provides hydrogen for the Calvin cycle</p> Signup and view all the answers

    What occurs during chemiosmosis in the thylakoid membrane?

    <p>Protons flow into the stroma through ATP synthase</p> Signup and view all the answers

    What is the purpose of grinding spinach leaves in the chloroplast extraction procedure?

    <p>To break down cell walls and release chloroplasts</p> Signup and view all the answers

    What happens to DCPIP during the Hill reaction?

    <p>It is reduced and loses its blue color</p> Signup and view all the answers

    Why is it important to zero the colorimeter with distilled water before measuring chloroplast extract?

    <p>To calibrate the device for accurate readings</p> Signup and view all the answers

    What is the effect of varying the distance of the tubes from the lamp in this experiment?

    <p>It impacts the light intensity and rate of photosynthesis</p> Signup and view all the answers

    What is indicated by a decrease in absorbance during the Hill reaction?

    <p>A reduction of DCPIP indicating increased photosynthesis activity</p> Signup and view all the answers

    What do the negative control tubes in this experiment demonstrate?

    <p>No change in absorbance without light exposure</p> Signup and view all the answers

    Which factor should remain constant when repeating the experiment to ensure reliable results?

    <p>The distance of the tubes from the lamp</p> Signup and view all the answers

    What is the purpose of resuspending the chloroplast pellet in chilled isolation solution?

    <p>To prevent degradation of chloroplasts before use</p> Signup and view all the answers

    Study Notes

    Photosynthesis: Light-Dependent Reactions

    • Photosynthesis is split into two stages: light-dependent and light-independent (Calvin cycle)
    • Light-dependent reactions need light energy
    • Light energy is absorbed by photosynthetic pigments in thylakoid membranes
    • Light energy is converted to chemical energy in the form of ATP and NADPH
    • Water is split, releasing H+ and electrons, producing oxygen as a waste product
    • ATP and NADPH are used in light-independent reactions
    • Light energy excites electrons in chlorophyll, which are transferred along an electron transport chain
    • Photolysis of water produces H+ (hydrogen ions), electrons, and O2
    • This process creates a proton gradient across the thylakoid membrane
    • The ATP synthase enzyme uses the proton gradient to make ATP from ADP and inorganic phosphate
    • Excited electrons lose energy as they move along the electron transport chain, this energy is used to make ATP
    • Electrons are transferred to NADP+, producing reduced NADP
    • Reduced NADP is used in light-independent reactions

    Photosynthesis: Light-Independent Reactions

    • Also called the Calvin cycle
    • Takes place in the stroma of chloroplasts
    • Doesn't directly use light energy
    • Uses the ATP and NADPH produced in light-dependent reactions
    • CO2 enters the leaf through the stomata and diffuses into the stroma of the chloroplast
    • CO2 is combined with ribulose bisphosphate (RuBP) by the enzyme RuBisCO
    • This forms an unstable 6-carbon compound, which quickly breaks down into two molecules of glycerate 3-phosphate (GP)
    • ATP and reduced NADP are required for the reduction of GP to glyceraldehyde 3-phosphate (GALP)
    • Two molecules of GALP can be used to make a hexose sugar (e.g., glucose)
    • RuBP is regenerated using the rest of the ATP produced by the light-dependent reaction

    Factors Affecting Photosynthesis

    • Light Intensity: Increases rate at first, then levels off
    • CO2 Availability: Increases rate at first, then levels off
    • Temperature: Increases rate to optimum, then decreases as enzymes denature

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    Description

    Test your knowledge on the various processes involved in photosynthesis, including the roles of photosystems, photophosphorylation, and the Calvin cycle. This quiz covers key questions about electron transfer, ATP production, and the effects of environmental factors on photosynthesis. Perfect for those studying plant biology or biochemistry!

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