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Plant Respiration and Bioenergetics
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Plant Respiration and Bioenergetics

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Questions and Answers

What does the succinyl-coA synthetase step produce in the Krebs Cycle of plant aerobic respiration?

  • ADP
  • GTP
  • ATP (correct)
  • NADH

    • What unique feature allows plant mitochondria to operate an alternative pathway for metabolism of PEP?

  • Presence of succinyl-coA synthetase
  • Significant NAD+-malic enzyme activity (correct)
  • High levels of GTP
  • Rotenone-sensitive NADH dehydrogenase

    • What is the main external feature of the dehydrogenase in the Electron Transport System of plants?

  • It oxidizes cystolic NADPH (correct)
  • It faces the mitochondrial matrix
  • It oxidizes pyruvate
  • It produces ATP from NADH

    • Which of the following statements regarding the inhibition of aerobic respiration in plants is correct?

    <p>It is strongly inhibited by certain agents.</p> Signup and view all the answers

    How many molecules of NADH are produced during glycolysis from one molecule of hexose in plant respiration?

    <p>2</p> Signup and view all the answers

    What mechanism is responsible for ATP formation during oxidative phosphorylation?

    <p>Controlled movement of H+ ions through ATP synthase</p> Signup and view all the answers

    What role do reduced coenzymes like FADH2 or NADH play in oxidative phosphorylation?

    <p>They provide high-energy electrons that drive electron transport.</p> Signup and view all the answers

    What is the primary function of the ATP-synthesizing enzyme during chemiosmotic phosphorylation?

    <p>To utilize the energy from electron transport to phosphorylate ADP.</p> Signup and view all the answers

    How does the chemiosmotic theory explain the formation of ATP?

    <p>It states that a proton concentration difference drives ATP synthesis.</p> Signup and view all the answers

    Which of the following compounds are known to inhibit oxidative phosphorylation?

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

    What happens to electrons as they move through the electron transport chain?

    <p>They result in the pumping of H+ ions across the membrane.</p> Signup and view all the answers

    What is the effect of uncoupling agents like dinitrophenol on oxidative phosphorylation?

    <p>They prevent the formation of a proton gradient.</p> Signup and view all the answers

    What is substrate-level phosphorylation?

    <p>ATP production driven by the transfer of a phosphate group from a donor molecule.</p> Signup and view all the answers

    What is the primary source of proteins encoded in the chloroplasts?

    <p>More than 95% are nuclear-encoded</p> Signup and view all the answers

    Which process directly requires molecular oxygen for normal plant metabolism?

    <p>Aerobic respiration</p> Signup and view all the answers

    What is a feature of the oxidation of hexose in aerobic respiration?

    <p>Controlled series of reactions</p> Signup and view all the answers

    What percentage of proteins in chloroplasts are encoded by the chloroplast genome?

    <p>About 5%</p> Signup and view all the answers

    What is one of the main roles of plant respiration?

    <p>Converts energy to metabolically useful forms</p> Signup and view all the answers

    Why do higher plants oxidize photoassimilates?

    <p>To obtain energy and carbon for growth</p> Signup and view all the answers

    Which of the following accurately describes aerobic respiration in higher plants?

    <p>It involves the oxidation of organic compounds</p> Signup and view all the answers

    In the oxidation of hexose, what is a significant outcome?

    <p>Energy is released in a controlled manner</p> Signup and view all the answers

    What effect does substrate starvation have on respiration in plants?

    <p>Leads to the utilization of proteins and fats.</p> Signup and view all the answers

    What happens to the Q10 value in most plants when temperatures exceed 30°C?

    <p>It decreases.</p> Signup and view all the answers

    What does increased temperature lead to in respiration rates, according to the content?

    <p>Decreased rates due to enzyme denaturation if prolonged.</p> Signup and view all the answers

    What indicates a lowering of aerobic respiration in plants on flooded soils?

    <p>Decreased O2 penetration and hypoxia/anoxia.</p> Signup and view all the answers

    What occurs during sundown in relation to photosynthates in plant leaves?

    <p>Accumulation of high sugar levels.</p> Signup and view all the answers

    What is the primary function of the alternative pathway in plant respiration?

    <p>Synthesizes ATP when the cytochrome pathway is saturated</p> Signup and view all the answers

    Which of the following plants is known for utilizing the alternative pathway during its floral development?

    <p>Skunk cabbage</p> Signup and view all the answers

    Which substrate is primarily used in the pentose phosphate pathway for the production of nucleic acids?

    <p>Ribose-5-phosphate</p> Signup and view all the answers

    What byproduct results from the pentose phosphate pathway besides NADPH?

    <p>Erythrose-4-phosphate</p> Signup and view all the answers

    What is a primary trigger for the activation of the alternative pathway?

    <p>Sufficient carbohydrates availability</p> Signup and view all the answers

    Which of the following is NOT a function of the pentose phosphate pathway?

    <p>Degrading glucose for ATP production</p> Signup and view all the answers

    What effect does temperature have on plant respiration?

    <p>Varies with the type and age of the plant</p> Signup and view all the answers

    How does the alternative pathway contribute to thermogenesis in plants?

    <p>By converting energy to heat instead of ATP</p> Signup and view all the answers

    In what way does NADP+ function differently in the pentose phosphate pathway compared to other pathways?

    <p>Serves as an electron acceptor</p> Signup and view all the answers

    What occurs during a respiratory crisis in the tissues of plants like skunk cabbage?

    <p>Surge in oxygen consumption</p> Signup and view all the answers

    Which component is NOT produced in the pentose phosphate pathway?

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

    Which condition can trigger the use of the alternative pathway in plants?

    <p>High levels of carbohydrates exceeding metabolic needs</p> Signup and view all the answers

    Which of the following best describes how temperature affects plant respiration?

    <p>Respiration rate is dependent on temperature and plant type</p> Signup and view all the answers

    What is the significance of the bulk of heat generated by certain pathways in plants?

    <p>It aids in pollination processes</p> Signup and view all the answers

    Study Notes

    Plant Respiration

    • Plants are aerobic organisms and need oxygen for respiration.
    • They use glucose to produce ATP through a controlled oxidation process in a series of smaller steps.
    • Chemiosmotic phosphorylation, explains how pH gradient drives the formation of ATP.
    • Oxidative phosphorylation is the process when ATP formation is driven by the energy released from electrons removed during substrate oxidation.
    • There is an alternative pathway for the reduction of oxygen, leading to cyanide-resistant respiration.
    • Plant mitochondria have unique features including:
      • a succinyl-coA synthetase step producing ATP instead of GTP.
      • a significant NAD+-malic enzyme activity for alternative metabolism of phosphoenolpyruvate.
      • an external dehydogenase that oxidizes cystolic NADPH.
      • a rotenone-insensitive NADH dehydrogenase.

    Bioenergetics of Respiration

    • For every glucose molecule, glycolysis produces 2 NADH.
    • The alternative pathway oxidase (AOX) is a homodimer spanning the inner mitochondrial membrane.
    • It functions as a ubiquinone O2 oxidoreductase, accepting electrons from the UQ-pool and transferring them directly to oxygen.
    • The energy that would have been conserved as ATP is converted to heat instead.

    Skunk Cabbage

    • Tissues of the spadix in skunk cabbage experience a surge in oxygen consumption, called respiratory crisis, causing a higher temperature.
    • This volatizes amines that attract insect pollinators.
    • The alternative pathway is generally not active, but becomes active when the cytochrome pathway is saturated, and the supply of carbohydrates increases.

    Pentose Phosphate Pathway

    • Also known as the hexose monophosphate shunt, oxidative pentose phosphate pathway, and phosphogluconate pathway.
    • The electron acceptor is NADP+ rather than NAD+.
    • The pathway's products include: NADPH, erythrose-4-phosphate, and ribose-5-phosphate.
    • NADPH is used for fatty acid biosynthesis.
    • Erythrose-4-phosphate is used for the production of phenolic compounds like anthocyanins and lignins.
    • Ribose-5-phosphate is used in nucleotides, RNA, and DNA.

    Factors Affecting Respiration

    • Substrate availability: Plants deficient in sugars or low substrate have low respiration rates.
    • Oxygen availability: Variations in oxygen content are generally small enough to not influence respiration. Oxygen penetration is generally sufficient to maintain normal respiration levels in mitochondria.
    • Temperature:
      • Respiration is temperature dependent.
      • The temperature coefficient (Q10) describes the effect of temperature.
      • Decreasing oxygen can minimize aerobic respiration without stimulating anaerobic respiration.
      • Pasteur effect describes the effect of oxygen on respiration during storage.
      • The rate of respiration decreases at high temperatures due to enzyme denaturation.

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    Explore the fascinating processes of plant respiration and bioenergetics. This quiz covers essential topics such as ATP production, chemiosmotic phosphorylation, and unique mitochondrial features in plants. Test your knowledge on how plants utilize glucose for energy and their alternative respiration pathways.

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