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Questions and Answers
What is the role of Glucose-6-phosphate dehydrogenase (GPD) in the oxidative phase?
What is the role of Glucose-6-phosphate dehydrogenase (GPD) in the oxidative phase?
What is the product of the oxidative phase that is converted to intermediates of glycolysis?
What is the product of the oxidative phase that is converted to intermediates of glycolysis?
What is the role of NADPH+H in RBC membrane integrity?
What is the role of NADPH+H in RBC membrane integrity?
What is the result of oxidation of thiol groups in hemoglobin?
What is the result of oxidation of thiol groups in hemoglobin?
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What is the function of reduced glutathione?
What is the function of reduced glutathione?
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What is the result of oxidation of membrane proteins?
What is the result of oxidation of membrane proteins?
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What is the byproduct of partial reduction of molecular oxygen?
What is the byproduct of partial reduction of molecular oxygen?
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What is the function of NADPH+H in reductive biosynthesis?
What is the function of NADPH+H in reductive biosynthesis?
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What is the function of glutathione peroxidase enzyme?
What is the function of glutathione peroxidase enzyme?
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What is the source of reducing electrons for glutathione reductase enzyme?
What is the source of reducing electrons for glutathione reductase enzyme?
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What is the primary source of NADPH in RBCs?
What is the primary source of NADPH in RBCs?
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What is the effect of G6PD deficiency on RBCs?
What is the effect of G6PD deficiency on RBCs?
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Why do persons with G6PD deficiency show increased resistance to Malarial infection?
Why do persons with G6PD deficiency show increased resistance to Malarial infection?
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What is the function of glucose-6-phosphate dehydrogenase (G6PD) in the HMP-shunt pathway?
What is the function of glucose-6-phosphate dehydrogenase (G6PD) in the HMP-shunt pathway?
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What is the consequence of Favism in individuals with G6PD deficiency?
What is the consequence of Favism in individuals with G6PD deficiency?
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Why is the HMP-shunt pathway important for RBC membrane integrity?
Why is the HMP-shunt pathway important for RBC membrane integrity?
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What is the function of NADPH in the regulation of RBC membrane integrity?
What is the function of NADPH in the regulation of RBC membrane integrity?
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What is the primary function of the pentose phosphate pathway?
What is the primary function of the pentose phosphate pathway?
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What is the role of NADPH in reductive biosynthesis?
What is the role of NADPH in reductive biosynthesis?
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What is the purpose of the Cori cycle?
What is the purpose of the Cori cycle?
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What is the site of the pentose phosphate pathway?
What is the site of the pentose phosphate pathway?
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What is the role of NADPH in the regeneration of glutathione?
What is the role of NADPH in the regeneration of glutathione?
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What is the function of the hexose monophosphate shunt?
What is the function of the hexose monophosphate shunt?
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What is the percentage of glucose that enters the pentose phosphate pathway?
What is the percentage of glucose that enters the pentose phosphate pathway?
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Study Notes
Hexose Monophosphate (HMP) Shunt
- About 10% of glucose per day enters this pathway, with the liver and RBCs metabolizing about 30% of glucose through this pathway.
Phases of HMP Shunt
Phase 1 (Oxidative Phase)
- Glucose-6-phosphate is oxidized, generating 2 molecules of NADPH, 1 molecule of pentose phosphate, and liberating 1 molecule of CO2.
- First reaction is catalyzed by Glucose-6-phosphate dehydrogenase (GPD), which is the rate-limiting step.
Phase 2 (Non-Oxidative Phase)
- Pentose phosphate is converted to intermediates of glycolysis.
Functions of NADPH+H
- Reductive biosynthesis (de novo synthesis of fatty acids and steroids).
- Maintenance of RBC membrane integrity:
- Reduced glutathione (GSH) helps maintain the reduced state of SH groups in proteins, including hemoglobin and membrane proteins.
- Oxidation of thiol groups in hemoglobin leads to denaturation of proteins and precipitation of insoluble mass inside RBCs (Heinz bodies).
- Oxidation of membrane proteins makes RBCs rigid, leading to removal from circulation by macrophages.
- Reduction of glutathione:
- NADPH+H reduces GS-SG into GSH, protecting thiol groups of cellular proteins from oxidation.
- Reduction of H2O2:
- NADPH+H reduces H2O2, a reactive oxygen species (ROS) that can cause damage to DNA, proteins, unsaturated lipids, and cell membranes.
Deficiency of G6PD (Favism)
- Favism is a hemolytic anemia, especially after ingestion of fava beans and certain compounds, such as antibiotics, anti-malarial, and antipyretics, which increase oxidative stress.
- Deficiency of G6PD occurs in all cells, but is most severe in RBCs, where HMP-shunt is the only source of NADPH.
- Other cells have alternative NADPH sources, such as NADPH-dependent malate dehydrogenase and NADPH-dependent isocitrate dehydrogenase.
- Persons with G6PD deficiency show increased resistance to malarial infection.
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Description
This quiz covers the two phases of the pentose phosphate pathway, including the oxidative phase and non-oxidative phase. It involves the conversion of glucose-6-phosphate and the generation of NADPH and pentose phosphate.