HOW ENZYMES PROBABLY WORK

Enzymes are globular proteins. Proteins have specific shapes, depending upon which amino acids are linked together and in what order. The way an enzyme is shaped presents an ACTIVE SITE (sometimes called active cleft).

This provides a platform for reactants or substrates, with such a specific shape that only substrates with the exact complementary shape can fit. The enzyme and substrates together are known as the ENZYME-SUBSTRATE COMPLEX.

By bringing the substrates so close together in an enzyme, the amount of energy required to react them together can be reduced. Thus the reaction takes place. Without the enzyme, the substrates would probably not even collide together and there would be no reaction at all.

The enzyme can be thought of as a lock and the substrate(s) as the key(s). Thus: the LOCK AND KEY model.Possibly the presence of the substrates changes the shape of an enzyme, so that they can fit into a newly formed active site. This is called the INDUCED FIT model.

Once the substrates have reacted together, they no longer fit in the active site of the enzyme and are released. This is the PRODUCT of the reaction.

The enzyme is thus available to repeat the same reaction.

Some reactions bring substrates together and make a complex product. These are known as SYNTHESIS reactions. Other reactions bring a complex into the active site and break it down into two or more products DEGRADATION reactions.John Osborne April 2015