Question:
Which of the following steps is specific for gluconeogenesis?
Which of the following steps is specific for gluconeogenesis?
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Look for the PEP carboxykinase bypass reaction.
Updated On: Jun 24, 2026
- Pyruvate to acetyl CoA
- Oxaloacetate to citrate
- Oxaloacetate to phosphoenolpyruvate (PEP)
- Malate to oxaloacetate
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The Correct Option is C
Solution and Explanation
Step 1: Gluconeogenesis is the making of glucose from non-carbohydrate sources. It largely reverses glycolysis but must bypass the three irreversible glycolytic steps using its own unique enzymes.
Step 2: One of these unique bypass reactions is the conversion of oxaloacetate to phosphoenolpyruvate (PEP), catalysed by PEP carboxykinase. This step belongs to gluconeogenesis and has no role in glycolysis or the citric acid cycle, so it is specific.
Step 3: Pyruvate to acetyl CoA (option a) is an irreversible step of pyruvate oxidation, not gluconeogenesis. Oxaloacetate to citrate (option b) and malate to oxaloacetate (option d) are steps of the citric acid cycle, which are shared with other pathways.
Step 4: Therefore the step specific for gluconeogenesis is oxaloacetate to PEP, making option c correct.
Step 2: One of these unique bypass reactions is the conversion of oxaloacetate to phosphoenolpyruvate (PEP), catalysed by PEP carboxykinase. This step belongs to gluconeogenesis and has no role in glycolysis or the citric acid cycle, so it is specific.
Step 3: Pyruvate to acetyl CoA (option a) is an irreversible step of pyruvate oxidation, not gluconeogenesis. Oxaloacetate to citrate (option b) and malate to oxaloacetate (option d) are steps of the citric acid cycle, which are shared with other pathways.
Step 4: Therefore the step specific for gluconeogenesis is oxaloacetate to PEP, making option c correct.
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