Enzymes
A large number of chemical reactions take place in living cells all the time. These reactions would normally occur outside the cells only at temperatures high enough to literally burn up the cells or would occur so slowly as to be useless, being unable to sustain life. The enzymes make the biochemical reactions go at ordinary temperature and virtually instantaneously.
The enzymes help in many biological reactions. Enzymes digest food in alimentary canal of animals which will starve without the enzymes. The enzymes are also essential for respiration, blood clotting, muscle contraction, nerve impulse transmission and so on.
Enzyme streptokinase is used in dissolving blood clot formed inside blood vessels. Enzymes are used as digestive aids in patients with faulty digestive juices. Enzymes are used in genetic engineering. They also have great industrial value too. They are used in making alcoholic beverages.
Enzymes are also used for retting of fibers, degumming of silk, food processing and chemical synthesis. The DNA of each cell contains the information necessary for the production of all the enzymes it requires.
All enzymes are produced in the living cells. These are of two types with regard to the site where they act-
1. Intracellular enzymes.
2. Extracellular enzymes.
1. Intracellular enzymes- are the enzymes which remain and function inside the cells.
2. Extracellular enzymes- are those enzymes which leave the cells and function outside them. They mainly include the digestive enzymes.
Most enzymes are proteins. They have a specific three dimensional, tertiary structure. Many enzymes contain certain non protein substances associated with them. These substances are called cofactors. The enzymes which function without a cofactor are called simple enzymes.
Being protein macromolecules, the enzymes have very high molecular weights. The enzymes do not start a chemical reaction but only accelerate it. The enzymes combine temporarily with the substrate molecules but are not consumed or changed permanently in the reaction they catalyze.
They enzyme controlled reactions are reversible. Most enzymes have high turnover number. The higher the turnover number, the more efficient the enzyme is. Not all enzymes are fast acting. Some are very slow.
The enzymes are specific in action. An enzyme may catalyze only a particular kind of reaction or act on specific substrate only. The enzymes are thermolabile. The enzymes generally work in teams in a cell.
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