Compare and contrast competitive and non-competitive enzymes inhibitors

Both competitive and non-competitive inhibitors interfere with the functioning of the enzyme's active site, reducing the number of enzyme-substrate complexes that can form. Competitive inhibitors have a shape similar to the substrate and therefore bind directly to the enzyme's active site. They therefore compete with the substrate for the active site. When the competitive inhibitor binds to the active site the substrate can no longer bind. On the other hand, Non-competitive inhibitors do not have a molecular shape similar to the substrate because they do not bind to the enzyme's active site. Instead they occupy an alternative region on the enzyme known as the 'allosteric site'. Upon attachment the inhibitor alters the shape of the enzyme; thus changing the shape of it's active site meaning the substrate can no longer bind. As the substrate and inhibitor are not in competition for the active site, an increase in substrate concentration does not decrease the effect of the inhibitor, which it would do in the case of competitive inhibition.