A Level Biology "Non-Competitive Inhibitors" | Freesciencelessons YouTube Video Summary

Non-Competitive Inhibitors on Enzymes

This video explains the effect of non-competitive inhibitors on enzyme catalysed reactions, and that by the end of the video viewers should be able to describe the effect of non-competitive inhibitors on the rate of an enzyme catalysed reaction.

Competitive Inhibitors Structure

The video refers to a previous video that looked at competitive inhibitors. Competitive inhibitors have a structure similar to the structure of the substrate molecule. A competitive inhibitor can bind to the active site of an enzyme and prevent the substrate molecule from binding there. The effect of this is to reduce the rate of the enzyme catalysed reaction. The effect of a competitive inhibitor can be reduced by increasing the concentration of the substrate. This increases the chance that a substrate molecule will enter the active site and form an enzyme-substrate complex before the competitive inhibitor enters, and remember that this only applies if the competitive inhibitor does not bind permanently to the active site.

Non-Competitive Inhibitors

Unlike a competitive inhibitor, non-competitive inhibitors do not bind to the active site of an enzyme. Instead, a non-competitive inhibitor binds to a different site on the enzyme molecule, called the allosteric site. When the non-competitive inhibitor binds to the allosteric site it causes the tertiary structure of the enzyme to change, and this means that the shape of the active site changes, so it is no longer complementary to the substrate. Now the substrate molecule cannot bind to the active site to form the enzyme-substrate complex. The effect of this is to reduce the rate of the reaction.

Non-Competitive Inhibitors Facts

Unlike a competitive inhibitor, a non-competitive inhibitor does not have a similar structure to the substrate. The effect of a non-competitive inhibitor cannot be overcome by increasing the substrate concentration, that’s because the non-competitive inhibitor causes the shape of the active site to change so even if we increase the concentration of substrate the substrate molecules still cannot bind successfully with the active site.