Pathways for the Metabolism of Carbohydrates

CARBOHYDRATE BIOCHEMISTRY A. Pathways for the Metabolism of Carbohydrates a. Introduction 

The term glycolysis was used to denote the disappearance of carbohydrate during metabolic activity. Warburg used the term to indicate the production of lactic acid from glucose in animal tissue. Glycolysis has also been used as a term to describe the sequence of reactions taking place in cells 

Acetaldehyde + CO2 ---------Pyruvic, phospho-enol-pyruvic acid  

The best-known glycolytic pathway is that studied especially in muscle tissue and yeast cells. This pathway, sometimes known as the Embden-Meyerhof-Parnas (EMP) scheme, is shown in Fig. 8. The reactions take place under anaerobic conditions. In yeast the end-products are ethanol and carbon dioxide, whereas in muscle tissue the end-product is L-lactic acid. The EMP scheme is operative in a great many tissues and organisms and apparently represents the major pathway of carbohydrate breakdown. 

The existence of the EMP pathway is based on several lines of evidence the presence of the intermediates in the system, the isolation and characterization of one or more of the enzymes involved, and the metabolism or disappearance of one or more of the intermediates when added to a tissue extract. 

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