Citric Acid Cycle Overview
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Questions and Answers

What is another name for the citric acid cycle?

  • Tricarboxylic acid cycle (correct)
  • Glycolysis cycle
  • Beta-oxidation cycle
  • Oxidative phosphorylation cycle
  • Where does the citric acid cycle occur in the cell?

  • Cytosol
  • Nucleus
  • Mitochondria (correct)
  • Endoplasmic reticulum
  • Which molecule is the major source of acetyl CoA for the citric acid cycle?

  • Fructose
  • Glycerol
  • Pyruvate (correct)
  • Glucose
  • What is the final electron acceptor in the citric acid cycle?

    <p>Oxygen (O2) (A)</p> Signup and view all the answers

    Which of the following is converted to CO2 in the citric acid cycle?

    <p>Carbon skeletons of carbohydrates, amino acids, and fatty acids (D)</p> Signup and view all the answers

    What is the overall importance of the citric acid cycle in metabolism?

    <p>Oxidative catabolism of carbohydrates, amino acids, and fatty acids (A)</p> Signup and view all the answers

    What is the role of the pyruvate dehydrogenase complex (PDH complex)?

    <p>To convert pyruvate to acetyl CoA in the mitochondria (C)</p> Signup and view all the answers

    Which coenzyme is required for the enzyme pyruvate carboxylase (E1) in the PDH complex?

    <p>Thiamine pyrophosphate (TPP) (C)</p> Signup and view all the answers

    What is the role of citrate synthase in the citric acid cycle?

    <p>To catalyze the condensation of acetyl CoA and oxaloacetate to form citrate (D)</p> Signup and view all the answers

    Which statement about aconitase is correct?

    <p>It isomerizes citrate to isocitrate (A)</p> Signup and view all the answers

    What is the primary means of regulation for citrate synthase?

    <p>Substrate availability (C)</p> Signup and view all the answers

    Which of the following is NOT a coenzyme required by the PDH complex?

    <p>Adenosine triphosphate (ATP) (D)</p> Signup and view all the answers

    What is the role of aconitase in the TCA cycle?

    <p>Aconitase is inhibited by the plant toxin fluoroacetate. (C)</p> Signup and view all the answers

    What is the role of isocitrate dehydrogenase in the TCA cycle?

    <p>Isocitrate dehydrogenase catalyzes the irreversible oxidative decarboxylation of isocitrate. (A)</p> Signup and view all the answers

    What is the role of the α-ketoglutarate dehydrogenase complex in the TCA cycle?

    <p>The α-ketoglutarate dehydrogenase complex is inhibited by its products, NADH and succinyl CoA. (C)</p> Signup and view all the answers

    What is the role of succinate thiokinase in the TCA cycle?

    <p>Succinate thiokinase is a substrate-level phosphorylation reaction in the TCA cycle. (D)</p> Signup and view all the answers

    What is the role of succinate dehydrogenase in the TCA cycle?

    <p>Succinate dehydrogenase catalyzes the oxidation of succinate to fumarate. (C)</p> Signup and view all the answers

    Which statement about the TCA cycle is true?

    <p>The TCA cycle releases three CO2 molecules. (D)</p> Signup and view all the answers

    What is the role of fumarase in the citric acid cycle?

    <p>It catalyzes the hydration of fumarate to malate (C)</p> Signup and view all the answers

    How many pairs of electrons are transferred during one turn of the citric acid cycle?

    <p>Four pairs, three reducing $NAD^+$ and one reducing $FAD$ (C)</p> Signup and view all the answers

    What is the primary factor that regulates the citric acid cycle?

    <p>The supply of oxidized cofactors ($NAD^+$ and $FAD$) (D)</p> Signup and view all the answers

    Which of the following enzymes is NOT mentioned as being important for the regulation of the citric acid cycle?

    <p>Malate dehydrogenase (C)</p> Signup and view all the answers

    What is the fate of the two carbon atoms that enter the citric acid cycle as acetyl-CoA?

    <p>They are released as $CO_2$ (B)</p> Signup and view all the answers

    What is the primary factor that determines the rate of ATP utilization, which in turn regulates the citric acid cycle?

    <p>The rate of chemical and physical work in the cell (B)</p> Signup and view all the answers

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