Explain why typical fatty acids cannot participate in gluconeogenesis.

Question

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Answer 1

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Typical fatty acids cannot be turned into glucose because those with an even number of carbons-the typical form in the body-break down into acetyl- CoA molecules. Acetyl-CoA can never re-form into pyruvate; the step between pyruvate and acetyl-CoA is irreversible. The options for acetyl-CoA are forming ketones and/or combining with oxaloacetate in the citric acid cycle.

At the end of 1 cycle, no carbons from acetyl-CoA are left to turn into glucose; it is impossible to convert typical fatty acids into glucose.

The glycerol portion of a triglyceride is the part that can become glucose. Glycerol enters the glycolysis pathway and can follow the gluconeogenesis pathway from glyceraldehyde 3-phosphate to glucose. Glucose yield from glycerol is insignificant.