Citric Acid Cycle Functions Quiz
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Questions and Answers

Which enzyme condenses oxaloacetate with acetyl-CoA to form citrate in the citric acid cycle?

  • Aconitase
  • Pyruvate dehydrogenase
  • ATP-citrate lyase
  • Citrate synthase (correct)

    • What is the main function of the citric acid cycle?

  • Synthesize fatty acids
  • Oxidize acetyl-CoA to CO2 (correct)
  • Produce ATP from glucose
  • Convert pyruvate to lactate

    • Which process links glycolysis with the citric acid cycle?

  • Oxidative decarboxylation of pyruvate to acetyl-CoA (correct)
  • Isomerization of citrate to isocitrate
  • Conversion of succinyl-CoA to succinate
  • Formation of alpha-ketoglutarate from isocitrate

    • What is the amphibolic role of the citric acid cycle?

    <p>Link between catabolic and anabolic pathways</p> Signup and view all the answers

    Where are all the enzymes of the citric acid cycle located?

    <p>$ ext{Mitochondria}$</p> Signup and view all the answers

    Which enzyme is responsible for the irreversible hydrolysis of the thioester bond in acetyl-CoA?

    <p>ATP-citrate lyase</p> Signup and view all the answers

    Which enzyme catalyzes the formation of succinyl-CoA, an irreversible step in the citric acid cycle?

    <p>Alpha ketoglutarate dehydrogenase</p> Signup and view all the answers

    Which enzyme is responsible for the isomerization of citrate to isocitrate in the citric acid cycle?

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

    Which enzyme complex in the citric acid cycle is similar to the pyruvate dehydrogenase complex?

    <p>$ ext{Alpha ketoglutarate dehydrogenase}$</p> Signup and view all the answers

    Which molecule is liberated during the conversion of isocitrate to alpha ketoglutarate in the citric acid cycle?

    <p>$ ext{CO}_2$</p> Signup and view all the answers

    Malate is formed from fumarate by the enzyme

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

    Malate is oxidized to oxaloacetate by the enzyme

    <p>malate dehydrogenase</p> Signup and view all the answers

    During the citric acid cycle, two carbon dioxide molecules are removed in the following reactions: A. Step 3, oxalosuccinate to alpha ketoglutarate B. Step 4, ______

    <p>alpha ketoglutarate to succinyl-CoA</p> Signup and view all the answers

    Oxaloacetate may be viewed as a catalyst, which enters into the reaction, causes complete oxidation of acetyl- CoA and comes out of it without any change. Oxalo-acetate is an important junction point in

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

    The succinate dehydrogenase is competitively inhibited by

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

    Study Notes

    Citric Acid Cycle

    • The enzyme citrate synthase condenses oxaloacetate with acetyl-CoA to form citrate in the citric acid cycle.

    Function of Citric Acid Cycle

    • The main function of the citric acid cycle is to generate energy for the cell through the breakdown of acetyl-CoA derived from carbohydrates, fats, and proteins.

    Linking Glycolysis with Citric Acid Cycle

    • The process that links glycolysis with the citric acid cycle is the conversion of pyruvate to acetyl-CoA.

    Amphibolic Role of Citric Acid Cycle

    • The citric acid cycle plays an amphibolic role, meaning it is involved in both catabolic and anabolic processes.

    Location of Citric Acid Cycle Enzymes

    • All the enzymes of the citric acid cycle are located in the mitochondrial matrix.

    Enzymes of Citric Acid Cycle

    • The enzyme acetyl-CoA synthetase is responsible for the irreversible hydrolysis of the thioester bond in acetyl-CoA.
    • The enzyme α-ketoglutarate dehydrogenase catalyzes the formation of succinyl-CoA, an irreversible step in the citric acid cycle.
    • The enzyme aconitase is responsible for the isomerization of citrate to isocitrate in the citric acid cycle.
    • The enzyme complex α-ketoglutarate dehydrogenase in the citric acid cycle is similar to the pyruvate dehydrogenase complex.

    Citric Acid Cycle Reactions

    • During the citric acid cycle, two carbon dioxide molecules are removed in the reactions: Step 3, oxalosuccinate to alpha-ketoglutarate and Step 4, isocitrate to alpha-ketoglutarate.

    Importance of Oxaloacetate

    • Oxaloacetate may be viewed as a catalyst, which enters into the reaction, causes complete oxidation of acetyl-CoA and comes out of it without any change.
    • Oxaloacetate is an important junction point in carbohydrate, fat, and protein metabolism.

    Inhibition of Succinate Dehydrogenase

    • The succinate dehydrogenase is competitively inhibited by malonate.

    Conversion of Fumarate to Malate and Oxaloacetate

    • Malate is formed from fumarate by the enzyme fumarase.
    • Malate is oxidized to oxaloacetate by the enzyme malate dehydrogenase.

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    Description

    Test your knowledge of the functions of the citric acid cycle, including its role in oxidation, production of coenzymes, connection between catabolic and anabolic pathways, and synthesis of amino acids and nucleotides.

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