The most important metabolic pathways include glycolysis, the citric acid cycle, the pentose phosphate pathway, gluconeogenesis, and glycogen synthesis & degradation. Let us discuss some of these.

Glycolysis is regulated to perform its two rolls: 1) the conversion of glucose into pyruvate as part of ATP generation and 2) to serve as a source of biosynthetic precursors. A high level of ATP switches off phosphofructokinase, indicating that cellular energy needs are being met. A high level of citrate also switches off phosphofructokinase, indicating that the need for biosynthetic precursors is being met. Glycolysis is also deactivated by decreasing levels of F-2,6-BP in the liver, a change triggered in the liver by glucagon when blood glucose is low.

In the citric acid cycle, fuel enters as acetyl CoA. Oxidation is followed by chemiosmosis. Furthermore, the citric acid cycle provides many intermediates for biosynthesis.

The pentose phosphate pathway is important for the generation of NADPH for reductive biosynthesis and the formation of ribose 5-phosphate for nucleotide synthesis.

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