The most important metabolic crossroads include glucose 6-phosphate, pyruvate, and acetyl CoA.

Glucose 6-phosphate results from the phosphorylation of intercellular glucose. One of the following then occurs: glycogen synthesis, glycolysis, or formation of ribose 5-phosphate for the pentose phosphate pathway. The liver and kidneys possess glucose 6-phosphatase, which enables glucose to be released into the blood.

Pyruvate interconverts with lactic acid to shift metabolic burden from muscle to liver. Pyruvate may be transaminated to alanine. May be carboxylated to oxaloacetate then to phosphoenolpyruvate then to glucose 6-phosphate in gluconeogenesis. Pyruvate be oxidatively decarboxylated to acetyl CoA, which is irreversible, committing the pathway to the citric acid cycle or to the synthesis of lipids.

Acetyl CoA is formed by oxidative decarboxylation of pyruvate and the β-oxidation of fatty acids. Acetyl CoA is either completely oxidized in the citric acid cycle or taken up in the biosynthesis of cholesterol, ketone bodies (for transporting acyl units), or citrate for fatty acid synthesis.












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