Photosynthesis Quiz: Mechanisms and Functions
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Questions and Answers

What form of energy is captured during photosynthesis?

  • Nuclear energy
  • Chemical energy (correct)
  • Kinetic energy
  • Thermal energy

    • Which molecules are used to convert carbon dioxide to hexose phosphates during photosynthesis?

  • ATP and NADPH (correct)
  • GTP and NADH
  • AMP and NADH
  • ADP and NADP+

    • What is the primary role of phototrophs in an ecosystem?

  • Converting solar energy into chemical energy (correct)
  • Recycling nutrients from dead organisms
  • Decomposing organic matter
  • Consuming other organisms

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

    <p>Within membrane-bound structures (A)</p> Signup and view all the answers

    What is the primary function of the hydride ion (H:-) during the light-dependent reactions?

    <p>To reduce NADP+ to NADPH (B)</p> Signup and view all the answers

    Which of the following occurs during the dark (light-independent) reactions of photosynthesis?

    <p>Carbon dioxide is reduced to carbohydrate (B)</p> Signup and view all the answers

    What is the typical diameter of a chloroplast?

    <p>4-8 mm (A)</p> Signup and view all the answers

    What is the role of chlorophyll in photosynthesis?

    <p>Capturing light energy (A)</p> Signup and view all the answers

    Which metal ion is found within the tetrapyrrole ring of chlorophyll?

    <p>Magnesium (Mg2+) (C)</p> Signup and view all the answers

    What is the primary role of antenna pigments in photosynthesis?

    <p>To capture and transfer light energy to chlorophyll. (C)</p> Signup and view all the answers

    What connects Photosystem I (PSI) and Photosystem II (PSII) in the light-dependent reactions of photosynthesis?

    <p>Cytochrome <em>bf</em> complex (C)</p> Signup and view all the answers

    At which wavelength does P700, the reaction center chlorophyll in Photosystem I (PSI), absorb light maximally?

    <p>700 nm (C)</p> Signup and view all the answers

    What is the role of light energy in the Z-scheme of photosynthesis?

    <p>To convert P680 and P700 into excited molecules that are good reducing agents. (C)</p> Signup and view all the answers

    During the oxidation of 2 water molecules (2 H2O) in photosynthesis, how many molecules of NADPH are produced?

    <p>2 NADPH (B)</p> Signup and view all the answers

    What is the electrochemical gradient (ΔµH) primarily composed of?

    <p>A combination of membrane potential (ΔΨ) and pH differential (ΔpH). (D)</p> Signup and view all the answers

    What is the function of the CFo portion of the chloroplast ATP synthase?

    <p>It spans the thylakoid membrane and forms a pore for H+. (C)</p> Signup and view all the answers

    How many ATP and NADPH molecules are required for each CO2 molecule to be reduced to (CH2O) in carbohydrate synthesis?

    <p>3 ATP and 2 NADPH (C)</p> Signup and view all the answers

    What is the primary purpose of cyclic electron transport in photosynthesis?

    <p>To balance the ATP to NADPH ratio by producing ATP without NADPH. (A)</p> Signup and view all the answers

    In cyclic electron flow, which molecule donates electrons back to the plastoquinone (PQ) pool?

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

    What is the ultimate fate of the proton gradient (µH) generated during the light-dependent reactions of photosynthesis?

    <p>It is used by H+-ATP synthase to phosphorylate ADP. (A)</p> Signup and view all the answers

    Which of the following best describes the role of light in photosynthesis?

    <p>Light drives photosynthetic electron transport to generate µH. (A)</p> Signup and view all the answers

    Which of the following is the main role of light reactions in photosynthesis?

    <p>To generate ATP and NADPH. (A)</p> Signup and view all the answers

    Flashcards

    Photosynthesis

    Process converting CO2 and H2O into carbohydrates using solar energy.

    Light Reactions

    Membrane-bound reactions capturing solar energy, producing O2, ATP, and NADPH.

    Dark Reactions

    Light-independent reactions that convert CO2 into carbohydrates using ATP and NADPH.

    Chloroplast Structure

    Organelle with two membranes and extensive internal stacking for photosynthesis.

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    Chemiosmosis

    Process where H+ ions create ATP during light reactions.

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    Chlorophyll

    Photosynthetic pigment that captures light energy, mostly in chloroplasts.

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    NADPH

    Energy carrier produced during light reactions, used in dark reactions to convert CO2.

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    Z Scheme

    Illustration of electron flow during light reactions of photosynthesis.

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    Bacteriochlorophyll

    Pigments found in anaerobic photosynthetic bacteria, similar to chlorophyll.

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    Antenna pigments

    Pigments like carotenoids that help capture light energy for photosynthesis.

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    Photosystem I (PSI)

    A photosystem that absorbs light maximally at 700nm and contributes to electron transport.

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    Photosystem II (PSII)

    A photosystem that absorbs light maximally at 680nm, initiating the light reactions.

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    Photophosphorylation

    The synthesis of ATP reliant on light energy through ATP synthase.

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    Cyclic electron flow

    A process producing ATP without generating NADPH by recycling electrons.

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    ATP synthase

    An enzyme that synthesizes ATP using a proton motive force from the electron transport chain.

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    Thylakoid membrane

    The membrane in chloroplasts where light reactions of photosynthesis occur.

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    Proton motive force (PMF)

    The energy gradient created by protons across the membrane used to drive ATP synthesis.

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    Study Notes

    Photosynthesis Overview

    • Photosynthesis is a process converting atmospheric carbon dioxide (CO2) and water (H2O) into carbohydrates.
    • Solar energy is captured as ATP and NADPH.
    • ATP and NADPH are used to convert carbon dioxide to hexose phosphates.
    • Phototrophs are photosynthetic organisms, including some bacteria, algae, and higher plants.

    Photosynthesis 1 - Light Reactions

    • Light and dark reactions are parts of photosynthesis.
    • Light energy is captured for biochemical processes.
    • Specific light wavelengths are important for photosynthesis.
    • Photosynthesis takes place in chloroplasts.
    • The Z-scheme is a model of the electron flow in light reactions.

    Light Reactions and Dark Reactions

    • Light-dependent reactions are membrane-bound.
    • Light reactions release oxygen from water molecules.
    • Light reactions produce ATP and NADPH.
    • Dark reactions occur in the solution (stroma).
    • Dark reactions convert carbon dioxide to carbohydrates.
    • Dark reactions use energy from NADPH and ATP.

    Chloroplast Structure

    • Chloroplasts are 4-8 mm diameter organelles in plant cells.
    • Chloroplasts have two surrounding membranes.
    • Internal membranes are stacked as thylakoid membranes.
    • Thylakoids are stacked into grana.
    • The space surrounding the thylakoids is called stroma.

    Chlorophyll and Other Pigments

    • Chlorophyll is a major, abundant light-harvesting pigment.
    • Tetrapyrrole ring structure is similar to heme but with magnesium (Mg2+) instead of iron.
    • Other pigments like carotenoids, phycoerythrin, and phycocyanin are antenna pigments.
    • Antenna pigments capture light energy, especially in the green spectrum.
    • Antenna pigments transfer light energy to chlorophylls.

    Light Absorption and Photosystems

    • Light absorption occurs in two photosystems (PSI and PSII).
    • Photosystems are groups of proteins and pigments in the thylakoid membrane.
    • PSI is paired for P700 (absorbs light maximally at 700 nm).
    • PSII is paired for P680 (absorbs light maximally at 680 nm).
    • A Z-scheme model illustrates the electron flow.
    • PSII to PSI to NADP+.

    Z-Scheme

    • Z-scheme describes the path of electron flow and reduction potentials of components in photosynthesis.
    • Light energy converts P680 and P700 to excited molecules that are better electron donors.
    • Electron flow drives electron transfer uphill.
    • NADP+ is the final electron acceptor.
    • Water is oxidized to produce oxygen (O2), while NADPH is produced.

    Chemiosmosis

    • Chemiosmosis theory explains energy conversion during photosynthesis.
    • The formation of a transmembrane electrochemical gradient is key.
    • Protons (H+) are transferred across a membrane to create this gradient.
    • The gradient is used to drive protons through ATP synthase.
    • ATP synthase creates ATP from ADP and Pi.

    Photophosphorylation — H+ ATP Synthase

    • Photophosphorylation is an ATP synthesis process dependent on light energy.
    • Chloroplast ATP synthase has two major parts, CF0 and CF1.
    • CF0 spans the membrane, acting as a proton channel.
    • CF1 protrudes into the stroma, catalyzing ATP synthesis.
    • ATP is made from ADP and Pi.

    Cyclic Electron Flow and Phosphorylation

    • Cyclic electron flow produces ATP, bypassing NADPH production.
    • Energy for CO2 reduction generates 2 NADPH and 3ATP.
    • Cyclic flow increases proton motive force for greater ATP production.

    Summary of Photosynthesis

    • Photosynthesis uses light energy to fix carbon into sugar.
    • Light reactions capture light energy to reduce NADP+ and phosphorylate ADP.
    • Photosynthesis takes place in chloroplasts.
    • ATP and NADPH are the energy sources for cellular reactions.

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    Description

    Test your knowledge about the processes and components involved in photosynthesis. This quiz covers topics such as energy capture, the role of phototrophs, and the function of chlorophyll. Ideal for students studying biology or environmental science.

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