Pentose Phosphate Pathway - Lecture 23
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Questions and Answers

What is the primary function of the pentose phosphate pathway?

  • Oxidation of fatty acids
  • Production of glucose from non-carbohydrate sources
  • Generation of NADPH and ribose 5-phosphate (correct)
  • Synthesis of ATP
  • Which of the following tissues is NOT mentioned as being particularly important for the pentose phosphate pathway?

  • Adipose tissue
  • Liver
  • Muscle tissue (correct)
  • Testes
  • What is a product of the irreversible oxidative reactions in the pentose phosphate pathway?

  • Ribose 5-phosphate
  • 2 NADPH (correct)
  • Fructose 6-phosphate
  • Glyceraldehyde 3-phosphate
  • How does glucose 6-phosphate dehydrogenase facilitate the pentose phosphate pathway?

    <p>By oxidizing glucose 6-phosphate irreversibly</p> Signup and view all the answers

    Which metabolic process utilizes ribose 5-phosphate produced by the pentose phosphate pathway?

    <p>Nucleotide biosynthesis</p> Signup and view all the answers

    What is the primary regulation point of the pentose phosphate pathway?

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

    Which of the following is a clinical manifestation of G6PD deficiency?

    <p>Neonatal jaundice</p> Signup and view all the answers

    How is G6PD deficiency primarily inherited?

    <p>X-linked</p> Signup and view all the answers

    What evolutionary advantage has been associated with G6PD deficiency in female carriers?

    <p>Increased resistance to falciparum malaria</p> Signup and view all the answers

    What is the consequence of G6PD deficiency on red blood cells?

    <p>Impaired formation of NADPH</p> Signup and view all the answers

    Study Notes

    Pentose Phosphate Pathway (Lecture 23)

    • The pentose phosphate pathway, also called the hexose monophosphate pathway or 6-phosphogluconate pathway, occurs in the cytosol of cells.
    • It involves two irreversible oxidative reactions followed by reversible sugar-phosphate interconversions.
    • No ATP is directly consumed or produced in the pathway.

    Specific Objectives

    • Understand the function of the pentose shunt.
    • Explain the effect of glucose 6-P dehydrogenase deficiency.

    Pathway Overview

    • The pentose pathway is a shunt from glycolysis.
    • The pathway generates NADPH, a crucial biochemical reductant.
    • It produces ribose-5-phosphate, essential for nucleotide synthesis.
    • It provides a mechanism to utilize five-carbon sugars from the diet or carbohydrate breakdown.

    Irreversible Oxidative Reactions

    • The oxidative portion produces ribulose-5-phosphate, CO2, and two NADPH molecules per glucose-6-phosphate oxidized.
    • One glucose-6-phosphate oxidized yields two NADPH.

    Oxidative Stages

    • Glucose-6-phosphate is oxidized by glucose-6-phosphate dehydrogenase.
    • 6-phosphogluconolactone is hydrolyzed by gluconolactonase.
    • 6-phosphogluconate is oxidized by 6-phosphogluconate dehydrogenase, producing CO2.
    • Resulting ribulose-5-phosphate can be converted to ribose-5-phosphate (necessary for nucleotide synthesis).

    Site of Action

    • Important in liver, lactating mammary glands, and adipose tissue for fatty acid synthesis.
    • Important in testes, ovaries, placenta, and adrenal cortex for steroid hormone synthesis.
    • Important in red blood cells (RBCs) to maintain reduced glutathione.

    Reversible Nonoxidative Reactions

    • Occurs in all cell types synthesizing nucleotides and nucleic acids.
    • Enables ribulose-5-phosphate conversion to ribose-5-phosphate for nucleotide synthesis, or to glycolysis intermediates.

    Glucose-6-Phosphate Dehydrogenase (G6PD) Deficiency

    • G6PD deficiency is an inherited disease characterized by hemolytic anemia due to the inability to detoxify oxidizing agents.
    • G6PD deficiency inhibits RBCs from producing NADPH, which leads to hemolysis.
    • This deficiency is X-linked and results from multiple mutations.
    • Symptoms can include neonatal jaundice and a shorter lifespan in severe cases.
    • Resistance to falciparum malaria is observed in female carriers.

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    Description

    This quiz covers the pentose phosphate pathway, highlighting its significance in cellular metabolism. Understand the function of the pathway, its oxidative reactions, and the implications of glucose 6-P dehydrogenase deficiency. Test your knowledge on the generation of NADPH and ribose-5-phosphate.

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