Question

Which one of the following statements concerning gluconeogenesis is correct?

• A. It occurs in muscle
• B. It is stimulated by fructose 2,6-bisphosphate
• C. It is inhibited by elevated levels of acetyl CoA
• D. It is important in maintaining blood glucose during the normal overnight fast

Hint:

Liver makes glucose to keep levels normal between meals.

Answer 1

The Correct Option is D

Step 1: Gluconeogenesis is the synthesis of glucose from non-carbohydrate precursors. It occurs mainly in the liver (and to a smaller extent the kidney) and is essential for keeping blood glucose normal between meals.

Step 2: During an overnight fast, both glycogenolysis and gluconeogenesis maintain blood glucose. After roughly 30 hours liver glycogen is largely depleted, and gluconeogenesis becomes the only source of glucose. So option 4 is correct.

Step 3: Option 1 is wrong because muscle lacks glucose-6-phosphatase and cannot release free glucose, so it does not perform true gluconeogenesis. Option 2 is wrong because fructose 2,6-bisphosphate stimulates glycolysis and inhibits gluconeogenesis.

Step 4: Option 3 is wrong because acetyl CoA actually activates pyruvate carboxylase, the first committed gluconeogenic enzyme, thereby promoting (not inhibiting) gluconeogenesis.