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By Jamie Hale
The following article takes a look at the basic concepts applying to human metabolism.
Metabolism- sum of all the chemical changes occurring in a cell, a tissue, or the body.
Reactions occur through various pathways. In these pathways a cascade of events occur as one reaction results in another reaction. Most pathways can be classified as Catabolic( break down of complex molecules into simpler molecules) or Anabolic (complex products are formed from simple precursors). Each pathway is composed of multienzyme sequences, and each enzyme, in turn may exhibit important catalytic or regulatory features.
Catabolic reactions occur to capture chemical energy in the form of ATP from the degradation of energy rich fuel molecules. Catabolism also allows molecules in the diet or nutrient molecules stored in cells to be converted into building blocks needed for the synthesis of complex molecules. Catabolism provides the chemical energy necessary for the maintenance of the living cell. Generally, energy generation from degradation of complex molecules occurs in three stages.
Stages of Catabolism
1) complex molecules are broken down into simpler substances, proteins are degraded to amino acids, polysaccharides are degraded to monosaccharides, and triaglycerols to free fatty acids and glycerol
2) In the second stage, these diverse building blocks are further degraded to acetyl coa and a few other simpler molecules. Some energy is captured as ATP, but the amount is small compared with energy produced during third stage of catabolism
3) The tricarboxylic acid cycle is the final common pathway in the oxidation of fuel molecules such as acetyl CoA
Because it is counterproductive to have anabolic and catabolic processes occurring in cells simultaneously, (this is why it is hard to gain muscle to a significant degree while losing fat, different processes) there are many signals that switch on anabolic processes while switching off catabolic processes and vice versa. Most of the known signals are hormones and the molecules involved in metabolism itself. Endocrinologists have traditionally classified many of the hormones as anabolic or catabolic.
Cortisol is a corticosteroid hormone that is involved in the response to stress; it increases blood pressure and blood sugar levels and suppresses the immune system. Synthetic