Enzymes

Enzymes

Enzymes are biological catalysts. A catalyst is defined as a substance

that increases the rate of a chemical reaction without itself

undergoing any permanentchange. Enzymes do precisely this in living

things. Without them, the rate of the reactions would be so slow as to

cause serious, if not fatal, damage. Enzymes have two main functions:

To act as highly specific catalysts, and also to provide a way of

controlling reactions, the amount of enzyme determines how quickly the

reaction can proceed.

Enzymes are usually globular proteins (some have been found to be RNA

molecules that can act as enzymes) and have a specific

three-dimensional shape. Enzyme molecules have a complicated

three-dimensional shape due to the particular way the amino acid chain

that makes up the protein is folded. An enzymes three-dimensional

shape is called its tertiary structure. A few of the amino acids on

the surface of the molecule fold inwards to make a specific

indentation, called the active site, into which a particular substrate

can fit, this is the where the reactions occur. Enzymes are substrate

specific. The active site of each different enzyme has its own

particular tertiary structure, so only a substrate with a

complementary shape will fit; we say it has a highly specific shape.

In order to work, an enzyme must temporarily bond with a substrate;

the substrate binds to the active site mainly with hydrogen bonds.

Binding to the active site makes the substrate react more quickly. The

substance produced at the end of a reaction between an enzyme and a

substrate, is called the product. There may be more than one substrate

or more than one...

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...int has no effect because the substrate concentration

becomes the limiting factor. We call this the point of optimal

concentration. At a low substrate concentration there are many active

sites that are not occupied. This means that the reaction rate is low.

When more substrate molecules are added, more enzyme-substrate

complexes can be formed. As there are more active sites, and the rate

of reaction increases. Eventually, increasing the substrate

concentration yet further will have no effect. The active sites will

be saturated so no more enzyme-substrate complexes can be formed. We

call this the point of optimal concentration.

Enzymes are extremely valuable biological catalysts to living

organisms as they control biological processes and allow them to take

place in the conditions, which occur inside living organisms.