is a substance that reduces or decreases the activity of an enzyme. It inhibits the proper functioning of enzyme.
competitive inhibitors are those which mimics the shape of the actual substrate and binds to the active site.
Figure below explains the functioning, substrate comes and binds to enzyme undergoes product formation and releases the site, making it available for new substrate to come and bind.
when a competitive inhibitor is present which mimics the substrate and binds with the enzyme but is not converted to any product and competes for the enzyme active site with actual substrate.
in simple terms enzymes activity decrease in presence of Competitive inhibitor
in the figure below the enzyme kinetics is low at low concentration of substrate but as the substrate amount increases its activity also reaches back to its normal
Non-competitive inhibitors do not compete for the active site with substrate but does not allow substrate to bind at the active site.
These are actually of two types
1. Allosteric as shown in first figure BELOW, they bind at different position but actually causes change in the active site so new substrate moity cannot bind.
2. in the second figure BELOW the substrate is sterically hindered, blocking the active site so as substrate can not interact with the enzyme.
Figure 2 (sorry couldn't find any better resolution)
in simple terms Non-Competitive Inhibitors do not allow the substrate to bind at the active site.
in the figure below the enzyme activity is low at low concentration of substrate but as the substrate amount increases its activity cannot reach the normal level unlike the competitive inhibitor.