Questions and Answers
What is the product of the dehydrogenation and phosphorylation reaction in step 5 of glycolysis?
What is the function of NAD+ in step 5 of glycolysis?
What type of phosphorylation occurs in step 6 of glycolysis?
What is the function of phosphoglucomutase in step 7 of glycolysis?
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What is the effect of fluoride on enolase in step 8 of glycolysis?
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What is the product of the reaction catalyzed by pyruvate kinase?
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Why is fluoride added to blood when taking it for sugar estimation?
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Why is step 10 of glycolysis necessary in anaerobic conditions?
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What is the reactant that is converted to pyruvate in step 9 of glycolysis?
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What is the significance of lactate production in glycolysis?
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What is the type of reaction that occurs in step 6 and step 8 of glycolysis?
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What is the purpose of the reaction catalyzed by lactate dehydrogenase?
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Why does the cell need to couple steps 5 and 10 of glycolysis?
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What is the end product of anaerobic glycolysis?
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Why do red blood cells derive energy only through glycolysis?
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What is the fate of lactate produced in anaerobic glycolysis?
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Study Notes
Step 5 of Glycolysis
- Glyceraldehyde-3-phosphate is dehydrogenated and phosphorylated to 1,3-bisphosphoglycerate (1,3-BPG) with the help of NAD+.
- This reaction is reversible and has a high-energy bond.
- The enzyme involved is glyceraldehyde-3-phosphate dehydrogenase.
- NAD+ is reduced to NADH during this reaction.
Step 6 of Glycolysis
- The energy of 1,3-BPG is trapped to synthesize one ATP molecule with the help of bisphosphoglycerate kinase.
- This is an example of substrate-level phosphorylation.
- The reaction is reversible.
Step 7 of Glycolysis
- 3-phosphoglycerate is isomerized to 2-phosphoglycerate by shifting the phosphate group from the 3rd to the 2nd carbon atom.
- The enzyme involved is phosphoglucomutase.
- This reaction is readily reversible.
Step 8 of Glycolysis
- 2-phosphoglycerate is converted to phosphoenolpyruvate by the enzyme enolase.
- One water molecule is removed, and a high-energy phosphate bond is produced.
- The reaction is reversible, and enolase requires Mg++.
- Fluoride inhibits enolase irreversibly.
Step 9 of Glycolysis
- Phosphoenolpyruvate (PEP) is dephosphorylated to pyruvate by pyruvate kinase.
- One mole of ATP is generated during this reaction.
- This is an example of substrate-level phosphorylation.
- The pyruvate kinase is a key glycolytic enzyme, and this step is irreversible.
Step 10 of Glycolysis
- In anaerobic conditions, pyruvate is reduced to lactate by lactate dehydrogenase (LDH).
- LDH has five iso-enzymes, and the cardiac iso-enzyme will be increased in myocardial infarcts.
Significance of Lactate Production
- Steps 5 and 10 are coupled, and the regeneration of NAD+ is essential for smooth operation of the glycolytic pathway.
- In aerobic conditions, pyruvate enters the citric acid cycle for complete oxidation, while in anaerobic conditions, lactate enters the Cori's cycle.
- In RBCs, which lack mitochondria, glycolysis is the only source of energy production, and the end product is lactic acid.
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Description
Learn about the 5th step of glycolysis, where glyceraldehyde-3-phosphate is dehydrogenated and phosphorylated to 1,3-bisphosphoglycerate with the help of NAD+. Understand the role of glyceraldehyde-3-phosphate dehydrogenase and the high energy bond formation.
