Which of the following processes is primarily responsible for the increase in plasma glucose upon glucagon secretion?

The process primarily responsible for the increase in plasma glucose upon glucagon secretion is glycogenolysis. Glycogenolysis is the biochemical pathway through which glycogen, a stored form of glucose in the liver and muscle tissues, is broken down into glucose-1-phosphate. This process occurs primarily in the liver, where glucagon stimulates the conversion of glycogen to glucose.

When glucagon is secreted, particularly during fasting or low blood glucose levels, it binds to its receptors on liver cells, activating signaling pathways that enhance glycogenolysis. As glycogen is degraded, glucose is released into the bloodstream, thereby raising the plasma glucose levels.

Other processes mentioned, such as glycolysis, gluconeogenesis, and translation, while important metabolic pathways, do not primarily contribute to the immediate increase in plasma glucose in response to glucagon. Glycolysis involves the breakdown of glucose to produce energy, gluconeogenesis synthesizes glucose from non-carbohydrate substrates, and translation refers to protein synthesis. None of these directly increase the availability of glucose from glycogen stores in the liver in the context of glucagon's action.