Sunday, February 27, 2011

Enzyme: Biological Catalysts

Enzymes are one of the most important forms of protein in every organism's metabolic processes. The purpose of enzymes is to speed up chemical reactions, and they are involved in almost all chemical reactions in a living organism.
The concept of enzyme is that they speed up reactions by lower the activation energy needed for that reaction but without being consumed by the reaction.

Each enzyme has its very own distinct molecules that fit into it, this molecules is referred  as the substrate. The binding site of the substrate is called the active site.

The Induced-fit Model

After the substrate binds to the active site, the enzyme will automatically change its shape to further assist in the chemical reaction. This enzyme-substrate interaction is called induced-fit model. The result is a enzyme-substrate complex,  where the chemical reaction is ready to take place. 

Certain enzyme will require either inorganic cofactors or organic coenzymes before they can function properly. These may bind to the active site or bind weakly with the substrate. Similarly, each enzyme has its own unique inhibitors/activators to control each enzyme activity. These chemicals can switch the enzyme between the active form/inactive form, and therefore regulating the rate of chemical reactions within a cell.

Competitive inhibitors - these inhibitors are similar to the substrate as they bind to the active site of the enzyme and therefore competing with the substrate.

Noncompetitive inhibitors - these inhibitors attach to another site of the enzyme and changes the shape of the enzyme, deactivating the enzyme.

Allosteric regulation- this is one method of the cell to control the rate of chemical reactions. Each enzyme has sites called allosteric sites some distance away from the active site. Binding an activator to the allosteric site will result in the stability of an enzyme in its active form. However, an allosteric inhibitor will stabilize the inactive form of the enzyme

Feedback inhibition- this is one of the major method a cell use to control its metabolic pathways. In a chain reaction, where the product of one reaction becomes the reactant of the next, the final product of the chain can act as an inhibitor that inhibits the activity of a enzyme earlier in the chain. Therefore, the increase in the concentration of products will result in the decrease in the rate of further reaction.

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