Final answer:
Glucagon levels rise during low blood sugar to stimulate glucose release into the bloodstream, requiring the inactivation of Pyruvate Kinase (PK) in hepatocytes to prevent glucose consumption and thereby increase blood glucose levels.
Step-by-step explanation:
When glucagon levels rise in our bloodstream, it indicates that our blood glucose levels are below normal, often due to fasting or increased energy demands. To counteract this, glucagon inhibits the uptake of glucose by the liver and muscle cells and stimulates the liver to produce glucose through glycogenolysis and gluconeogenesis. Hepatocytes must inactivate Pyruvate Kinase (PK) during this process because PK is an enzyme involved in glycolysis, which converts glucose into energy. Inactivating PK helps to prevent glucose from being consumed for energy within the liver, thus favoring the release of glucose into the bloodstream to raise blood glucose levels back to the normal range.