Biology Module 1 - 4.enzymes 4.2 explain the mode of action of enzymes in terms of an active site, enzyme and/or substrate complex, lowering activation energy and enzyme specificity

4.2 explain the mode of action of enzymes in terms of an active site, enzyme and/or substrate complex, lowering activation energy and enzyme specificity

• enzyme catalyses reactions where substrates are broken down to products. Enzyme has an active site which is a pocket in an enzyme molecule and it is shaped so that the substrate can fit closely into it. This is the idea of lock and key.

• as a substrate molecule fits into the active site the enzyme changes slightly to mould itself around the substrate for a better fit. This mode of action is known as induced fit and this combination forms the enzyme-substrate complex.

• enzymes are specific because of the shape of the active site which must be complementary to the shape of the substrate

• enzymes provide active sites where substrates molecules are positioned in such a way that the activation energy is overcome