Question

Biochemistry Question

In hypoglycemia, the liver is not utilizing glucose as an energy source while the rest of the body continues to use glycolysis to generate ATP. Explain in detail why this happens. Also, why is the liver not using glucose?

Answer 1

Glycogen is converted to glucose in the liver in presence of glucagon hormone. This glucose enters the blood form the liver. Glucagon is synthesized by the alpha cells of islets of Langerhans in the pancreas in response to low glucose. The liver stores glycogen, which is broken down when there are low sugar levels. Hence, blood sugar levels are restored to normal.

Hypoglycemia is the reduced amount of glucose in blood. Gluconeogenesis is enhanced during hypoglycemia. When there is hypoglycemia, glucose levels decreases in blood, possibly due to decreased insulin production. To restore glucose levels, glucagon is released. Glucagon will inhibit glycolysis and promote gluconeogenesis. PFK2 is in an inactive form. Hence, fructose-2,6-bisphosphate is converted back to fructose-6-phosphate, which then forms glucose. Phosphorylase a is the glucose sensor in the liver. In absence of glucose, the phosphorylase a is inactive. Glycogen then gets broken down to glucose, which enters the blood circulation and is transported to other organs to be used as energy source. As a result, glucose levels decrease in the liver. Hence, the liver has no glucose left to utilize as an energy source. The liver will try to make more sugars from amino acids, lactic acid, and glycerol. Ketone bodies are also made by the liver from fats in hypoglycemia, for organs that can use it. Rest glucose is transported to organs that need glucose. Glucagon only acts on liver cells. It has no effect on glycolysis in other organs.