Figure 77-4 Gluconeogenesis from various precursors. The diagram shows the stages in which amino acids (e.g., alanine), glycerol, and lactate join the pathway of gluconeogenesis. The reactions common to gluconeogenesis and glycolysis are those indicated by the straight arrows; the downward arrows show the direction of gluconeogenesis, the upward arrows the direction of glycolysis. The curved arrows represent the reactions (i.e., pyruvate carboxylase, phosphoenolpyruvate carboxykinase, fructose-1,6-diphosphatase, and glucose-6-phosphatase) circumventing the energy barriers obstructing the direct reversal of glycolysis. (Adapted from Biebuyck JF: Anaesthesia and hepatic metabolism: Current concepts of carbohydrate homeostasis. Anesthesiology 39:188, 1973.)