23 Mar

Metabolism

The total sum of the chemical reactions that occur in a cell are referred to as metabolism and the individual reactions make up the metabolic pathways.  Proteins called enzymes catalyze or speed up the rate of these metabolic pathways.  Most enzymes catalyze reactions inside the cell and carry out the breakdown or catabolism of food and the biosynthesis of cell constituents or anabolism.  Bacteria can’t phagocytose or engulf nutrients due to their cell wall therefore they are forced to excrete enzymes that degrade molecules outside of the cell.  Exoenzymes break down polysaccharides and proteins into monosaccharides and amino acids which are then transported into the cell.  Protease, DNase and amylase are examples of exoenzymes.  Some enzymes are assisted by coenzymes.  Coenzymes transfer small molecules from one molecule to another.  Most co enzymes derive from vitamins.  NAD+ is derived from niacin and FAD comes from folic acid.  Coenzymes are only required by a cell in small amounts.