Explain what happens to the following metabolic pathways in the liver during a f

Question

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.

Glycolysis and Gluconeogenesis

Glycogenesis and Glycogenolysis

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

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

Explanation / Answer

Ans.) Glycolysis is a metabolic process which converts glucose into pyruvate and during the process, the free energy released is used to form ATP molecules and NADH. Now during fasting, the hepatocytes move over to the Fatty acid beta - oxidation for the energy requirements. The key metabolic enzyme controlling these is phosphofructo-kinase. The rate of glycolysis and glycogenesis decreases whereas that of gluconeogenesis and glycogenolysis increases due to the activity of this above mentioned enzyme during the fasting state. The net result is an increase in the hepatocyte glucose production or HGP.

The main source of energy during the first 16 hours of fasting is the glycogen stored in the hepatocytes.In muscle the rate of pyruvate oxidation decrease is caused by the enzyme pyruvate kinase as the body switches to the ketosis for energy consumption.

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