(8 pts) Explain what happens to the following metabolic pathways in the liver du

Question

(8 pts) Explain what happens to the following metabolic pathways in the liver during a fasted state. Identify the key metabolic enzymes controlling the overall activity of each of the pathways listed and their phosphorylation state.

a.) Glycolysis and Gluconeogenesis

b.) Glycogenesis and Glycogenolysis

c.) What is the main source of blood glucose during the first 16 hrs of fasting and why is that the case?

d.) In muscle, the rate of pyruvate oxidation also decreases during this fast. What is controlling this process in muscle?

Explanation / Answer

Important Enzymes used in Glycolysis and Gluconeogenesis:

Hexokinase- Conversion of glucose to glucose 6 phosphate.

Phosphogluco isomerase- conversion of glucose-6-phosphate to fructose-6-phosphate (F6P)

Phosphofructokinase- conversion of fructose-6-phosphate to fructose- 1,6-bisphosphate (FBP)

3-phosphoglycerate kinase.

Aldolase- catalyzes the cleavage of FBP to yield two 3-carbon molecules.

Hepatic gluconeogenesis is the main source of blood glucose during the first 16 hrs of fasting.

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