Friday, January 29, 2010

Metabolic Pathways

Metabolic pathways are series of chemical reactions which take place within a cell. In each metabolic pathway, a principal chemical is modified by chemical reactions. Enzymes catalyze these reactions, and often require dietary minerals, vitamins, and other cofactors in order to function properly. Because of the many chemicals that may be involved, metabolic pathways can be quite elaborate. In addition, many pathways can exist within a cell. This collection of pathways is called the metabolic network. Pathways are important to the maintenance of homeostasis within an organism.

There is a very large number of metabolic pathways. In humans, the most important metabolic pathways are:

1) glycolysis, which is glucose oxidation in order to obtain Adenosine triphosphate (ATP); 2) citric acid cycle (Krebs' cycle), which is acetyl-CoA oxidation in order to obtain GTP and valuable intermediates; 3) oxidative phosphorylation, which is the disposal of the electrons released by glycolysis and citric acid cycle; 4) pentose phosphate pathway, which is the synthesis of pentoses and release of the reducing power needed for anabolic reactions; 5) urea cycle, which is the disposal of NH4+ in less toxic forms; 6) fatty acid b-oxidation, which is the breakdown of fatty acids into acetyl-CoA, to be used by the Krebs' cycle; 7) gluconeogenesis, which is glucose synthesis from smaller percursors, to be used by the brain.