Describe competitive and non-competitive inhibition of enzyme action.

To start with, let’s just quickly define an enzyme. An enzyme is a biological molecule that is able to speed up a reaction. Without the presence of enzymes, certain reactions just wouldn’t be able to take place at all. Importantly, enzymes are able to remain unchanged at the end of reactions and this means they can then be re-used by other molecules. The substrates are the molecules that enzymes act one and have binding sites for their specific enzymes. It is the shape of these sites which confers the specificity to these reactions. The shape of an enzyme is said to be complementary to its substrate and the fit together in what is commonly known as a lock and key mechanism. Inhibitors stop the action of enzymes and they do this by altering their shape and preventing interactions of their active sites. Inhibitors can bind to the active site of an enzyme which stops it being able to bind to the substrate. This is known as competitive inhibition as both the inhibitor and the substrate are competing for the active site of the enzyme. Alternatively, enzymes can bind allosterically at another site to the active one. The binding of this inhibitor causes a conformational shape change of the enzyme, rendering it permanently unable to bind its substrate and catalyse the reaction. An important factor to remember is that for competitive inhibition, once the inhibitor in unbound then the enzyme can act as normal. But for non-competitive inhibition this is not the case and the enzyme is rendered useless.