BC Pentose Phosphate Pathway
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Questions and Answers

Which pathway is often referred to as a Hexose monophosphate shunt?

  • Krebs cycle
  • Pentose Phosphate Pathway (correct)
  • Glycolysis
  • Gluconeogenesis

    • Which of the following is NOT a product of the pentose phosphate pathway?

  • NADPH
  • ATP (correct)
  • Reduced glutathione
  • Fatty acids

    • Which phase of the pentose phosphate pathway generates NADPH?

  • Non-oxidative Phase
  • Glycolytic Phase
  • Krebs cycle
  • Oxidative Phase (correct)

    • What is the main function of NADPH in the pentose phosphate pathway?

    <p>To be used in anabolic reactions requiring electrons</p> Signup and view all the answers

    Which of the following is a tissue with active pentose phosphate pathway?

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

    Which glycolytic intermediate does the pentose phosphate pathway begin with?

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

    Which of the following is a product of the pentose phosphate pathway?

    <p>Glyceraldehyde 3-P</p> Signup and view all the answers

    What is the main function of reduced glutathione synthesized by the pentose phosphate pathway?

    <p>To protect cells from oxidative damage</p> Signup and view all the answers

    What is the pentose sugar produced by the pentose phosphate pathway?

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

    Where does the pentose phosphate pathway take place?

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

    Which enzyme is highly specific for NADP+ and is the first site for NADPH formation in the pentose phosphate pathway?

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

    Which enzyme is responsible for converting ribulose-5-P into xylulose-5-P in the nonoxidative phase of the pentose phosphate pathway?

    <p>Ribulose-5-P-epimerase</p> Signup and view all the answers

    Which coenzyme is required by transketolase and pyruvate dehydrogenase in their respective reactions?

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

    Which enzyme in the citric acid cycle also has a requirement for thiamine pyrophosphate?

    <p>α-Ketoglutarate oxidoreductase</p> Signup and view all the answers

    What is the product of the reaction between sedoheptulose 7-P and glyceraldehyde-3-P in the pentose phosphate pathway?

    <p>Fructose-6-P + Erythrose-4-P</p> Signup and view all the answers

    Which enzyme is most directly impaired in individuals suffering from G6PD deficiency?

    <p>Glutathione peroxidase</p> Signup and view all the answers

    Which enzyme is responsible for breaking the bond between C2-C3 of a keto sugar in the pentose phosphate pathway?

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

    A man is given antibiotics to treat a bacterial infection and develops an episode of red blood cell lysis. Which of the following enzymes is most likely defective in this patient?

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

    Which enzyme is responsible for breaking the bond between C3-C4 of a keto sugar in the pentose phosphate pathway?

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

    What is the regulatory enzyme in the Pentose Phosphate Pathway?

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

    Which pathway can account for the complete oxidation of glucose?

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

    What is the tri-peptide composed of glutamate, cysteine, and glycine?

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

    Which vitamin deficiency can lead to beri-beri, a debilitating disease?

    <p>Vitamin B1</p> Signup and view all the answers

    What is the function of reduced glutathione (GSH) in red blood cells?

    <p>Maintain cysteine residues in hemoglobin</p> Signup and view all the answers

    Which brain function is affected by thiamine deficiency?

    <p>All of the above</p> Signup and view all the answers

    Which condition is often clinically seen as black urine under certain conditions?

    <p>G6PD deficiency</p> Signup and view all the answers

    Which enzyme converts oxidized glutathione (G-S-S-G) to reduced glutathione (G-SH)?

    <p>Glutathione reductase</p> Signup and view all the answers

    What is the main role of NADPH in the Pentose Phosphate Pathway?

    <p>To regenerate GSH from GSSG</p> Signup and view all the answers

    What is the ratio that usually inhibits the Glucose 6-phosphate dehydrogenase enzyme?

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

    What is the role of glutathione peroxidase in the presence of reduced glutathione (GSH)?

    <p>Break down hydrogen peroxide</p> Signup and view all the answers

    Study Notes

    Pentose Phosphate Pathway

    • The pentose phosphate pathway is also referred to as the Hexose monophosphate shunt.
    • ATP is NOT a product of the pentose phosphate pathway.
    • The oxidative phase of the pentose phosphate pathway generates NADPH.
    • The main function of NADPH in the pentose phosphate pathway is to provide reducing power for various biochemical reactions.

    Tissues and Function

    • Erythrocytes, testes, and lactating mammary glands are tissues with active pentose phosphate pathway.
    • The pentose phosphate pathway begins with glucose-6-phosphate, a glycolytic intermediate.

    Products and Byproducts

    • Ribose-5-phosphate is a product of the pentose phosphate pathway.
    • The main function of reduced glutathione synthesized by the pentose phosphate pathway is to protect RBCs against oxidative damage.

    Enzymes and Coenzymes

    • Glucose-6-phosphate dehydrogenase is the first site for NADPH formation in the pentose phosphate pathway and is highly specific for NADP+.
    • Phosphopentomutase is the enzyme responsible for converting ribulose-5-P into xylulose-5-P in the nonoxidative phase of the pentose phosphate pathway.
    • Thiamine pyrophosphate is the coenzyme required by transketolase and pyruvate dehydrogenase in their respective reactions.
    • α-Ketoglutarate dehydrogenase is the enzyme in the citric acid cycle that also has a requirement for thiamine pyrophosphate.

    Pathway Reactions

    • The reaction between sedoheptulose 7-P and glyceraldehyde-3-P in the pentose phosphate pathway produces erythrose 4-phosphate and fructose 6-phosphate.
    • Aldolase is the enzyme responsible for breaking the bond between C2-C3 of a keto sugar in the pentose phosphate pathway.
    • Aldolase is also responsible for breaking the bond between C3-C4 of a keto sugar in the pentose phosphate pathway.

    Deficiencies and Diseases

    • Glucose-6-phosphate dehydrogenase (G6PD) deficiency can lead to hemolytic anemia, which can cause red blood cell lysis.
    • G6PD deficiency is often clinically seen as black urine under certain conditions.

    Vitamin Deficiencies

    • Thiamine (Vitamin B1) deficiency can lead to beri-beri, a debilitating disease.
    • Wernicke-Korsakoff syndrome is a brain disorder caused by thiamine deficiency.

    Glutathione

    • Glutathione is a tri-peptide composed of glutamate, cysteine, and glycine.
    • Reduced glutathione (GSH) protects RBCs against oxidative damage.
    • Glutathione reductase is the enzyme that converts oxidized glutathione (G-S-S-G) to reduced glutathione (G-SH).
    • Glutathione peroxidase, in the presence of reduced glutathione (GSH), reduces hydrogen peroxide to water.

    Regulation and Ratio

    • Glucose-6-phosphate dehydrogenase is the regulatory enzyme in the Pentose Phosphate Pathway.
    • A high NADPH/NADP+ ratio usually inhibits the Glucose 6-phosphate dehydrogenase enzyme.

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