Q: Distinguish between competitive and non-competitive inhibition of enzymes

A competitive inhibitor is structurally similar to the substrate but a non-competitive inhibitor is often structurally different from the substrate. Hence, a competitive inhibitor will compete with the substrate for an active site but a non competitive inhibitor will bind to the allosteric site of the enzyme, away from the active site. A competitive inhibitor does not change the three dimensional (secondary and tertiary structure) of an enzyme, but a non-competitive inhibitor always changes its structure. A competitive inhibitor will not affect the active site of the enzyme, but a non-competitive inhibitor will alter the active site of the enzyme such that it is no longer complementary in size, shape, and charge to the substrate. The effects of competitive inhibition can be overcome but increasing substrate concentration, thus increasing the chance of forming enzyme-substrate complex but the effects of non-competitive inhibition cannot be overcome by increasing substrate concentration, but only by increasing enzyme concentration. The effects of competitive inhibition are usually temporary but the effects of the non-competitive inhibition are permanent.