What is the process of forming glucose from various metabolic intermediates called?

The process of forming glucose from various metabolic intermediates is called gluconeogenesis. This pathway allows the body to synthesize glucose from non-carbohydrate sources, such as amino acids or glycerol, particularly during periods of fasting or intense exercise when glucose levels in the blood may drop. Gluconeogenesis primarily occurs in the liver and, to a lesser extent, in the kidneys.

During this process, precursors are converted through a series of enzymatic reactions that essentially reverse some steps of glycolysis, albeit using different enzymes for the irreversible steps of glycolysis. This is crucial for maintaining blood glucose levels and ensuring that cells, particularly in the brain and red blood cells, have a steady supply of glucose for energy.

The other processes listed do not serve the same function. Glycolysis is the breakdown of glucose to produce energy, whereas the citric acid cycle is responsible for further breaking down the products of glycolysis. Fermentation is an anaerobic process that generates energy without oxygen but does not produce glucose from non-carbohydrate sources. Thus, gluconeogenesis is distinct in its role as a glucose-producing pathway.