Lecture 31 – Gluconeogenesis and Pentose Phosphate Pathway
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Questions and Answers

What is the primary purpose of gluconeogenesis?

  • To convert pyruvate into glucose (correct)
  • To produce ATP
  • To generate NADPH
  • To break down glucose for energy

    • Which enzyme catalyzes the phosphorylation of glucose to glucose-6-phosphate in glycolysis?

  • Hexokinase (correct)
  • Pyruvate kinase
  • Phosphofructokinase
  • Glyceraldehyde-3-phosphate dehydrogenase

    • What is the nature of reactions with a large negative ΔG in metabolic pathways?

  • They are reversible.
  • They are independent of substrate concentration.
  • They are irreversible. (correct)
  • They require ATP.

    • Which compound can serve as a starting material for gluconeogenesis?

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

    What is the role of NADPH in the pentose phosphate pathway (PPP)?

    <p>Biosynthesis and antioxidant defense</p> Signup and view all the answers

    What are the two main stages of the pentose phosphate pathway?

    <p>Oxidative and non-oxidative</p> Signup and view all the answers

    Which enzyme catalyzes the conversion of glucose-6-phosphate to ribulose-5-phosphate?

    <p>Glucose-6-phosphate dehydrogenase</p> Signup and view all the answers

    In the oxidative phase of the PPP, how many NADPH molecules are produced from one molecule of glucose-6-phosphate?

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

    Which enzyme catalyzes the conversion of glucose-6-phosphate to ribulose-5-phosphate?

    <p>Glucose-6-phosphate dehydrogenase</p> Signup and view all the answers

    What is the outcome of the non-oxidative phase of the PPP?

    <p>Production of ribose-5-phosphate and glycolytic intermediates</p> Signup and view all the answers

    What is the main regulatory step in the pentose phosphate pathway?

    <p>Conversion of glucose-6-phosphate to ribulose-5-phosphate</p> Signup and view all the answers

    What is the primary function of ribose-5-phosphate produced in the PPP?

    <p>DNA and RNA synthesis</p> Signup and view all the answers

    In which mode of the PPP is ribose-5-phosphate maximized?

    <p>Mode 1</p> Signup and view all the answers

    Which pathway produces ribose-5-phosphate needed for nucleotide synthesis?

    <p>Pentose phosphate pathway</p> Signup and view all the answers

    What condition leads to the activation of glycolytic intermediates in the PPP?

    <p>High ribose-5-phosphate demand</p> Signup and view all the answers

    Favism is associated with a deficiency in which enzyme?

    <p>Glucose-6-phosphate dehydrogenase</p> Signup and view all the answers

    What is a consequence of glucose-6-phosphate dehydrogenase deficiency?

    <p>Hemolytic anemia</p> Signup and view all the answers

    Which compound is NOT a substrate for gluconeogenesis?

    <p>Acetyl-CoA</p> Signup and view all the answers

    What is the net reaction for the oxidative phase of the PPP?

    <p>Glucose-6-P + 12 NADP+ + 7 H2O → 6 CO2 + 12 NADPH + 12 H+ + Pi</p> Signup and view all the answers

    What is the role of NADP+ in the oxidative phase of the PPP?

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

    In which cellular location does gluconeogenesis primarily occur?

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

    Which of the following best describes a futile cycle?

    <p>A cycle that consumes energy without producing useful work</p> Signup and view all the answers

    What is the end product of the oxidative phase of the PPP?

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

    What is the significance of the cyclic mode of the PPP?

    <p>It maximizes ATP production.</p> Signup and view all the answers

    In which scenario would a cell primarily utilize Mode 3 of the PPP?

    <p>Adipose tissue or red blood cells needing NADPH</p> Signup and view all the answers

    Which of the following is an example of an anaplerotic reaction?

    <p>Conversion of pyruvate to oxaloacetate</p> Signup and view all the answers

    What is the main energy cost associated with gluconeogenesis?

    <p>Consumption of ATP and GTP</p> Signup and view all the answers

    Which of the following processes is directly inhibited by malonate?

    <p>Citric acid cycle</p> Signup and view all the answers

    What happens to the levels of NADPH during oxidative stress?

    <p>They remain unchanged.</p> Signup and view all the answers

    What is the primary function of the non-oxidative phase of the PPP?

    <p>Production of intermediates for nucleotide synthesis</p> Signup and view all the answers

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