Principles of Biochemistry

3.4.1.3.Carbohydrate metabolism

1. Carbohydrate metabolism

It is centered on the provision and fate of glucose. Glucose is metabolized to pyruvate and lactate in all mammalian cells by the pathway of glycolysis. Glucose is a unique substrate because glycolysis can outline of the pathways for the catabolism of dietary carbohydrate, protein, and fat. All the pathways lead to the production of acetyl-CoA, which is oxidized in the citric acid cycle, ultimately yielding ATP in the process of oxidative phosphorylation. Occur in the absence of oxygen (anaerobic)are able to metabolize pyruvate to acetyl-CoA, which can enter the citric acid cycle for complete oxidation to CO₂  and H₂O, with liberation of much free energy as ATP in the process of oxidative phosphorylation.

Glucose is a major fuel of many tissues. But it (and some of its metabolites) also takes part in other processes,

e.g. (1) Glycogenesis- the conversion to its storage polymer, glycogen, particularly in skeletal muscle and liver.

(2) the pentose phosphate pathway, which arises from intermediates of glycolysis.  It is a source of reducing equivalents (2H) for biosynthesis e.g., of fatty acids-and it is also the source of ribose, which is important for nucleotide and nucleic acid formation.

(3) Triose phosphate gives rise to the glycerol moiety of acylglycerols (fat). (4) Pyruvate and intermediates of the citric acid cycle provide the carbon skeletons for the synthesis of amino acids, and acetyl-CoA is the building block for long-chain fatty acids and cholesterol, the precursor of all steroids synthesized in the body.

(5)Gluconeogenesis is the process that produces glucose from non-carbohydrate precursors, e.g. lactate, amino acids, and glycerol.