There are two types of inhibitors. Competitive inhibitors have a similar tertiary structure to the substrate and so can bind temporarily to the enzyme’s active site. This blocks the active site meaning the substrate can’t bind. The rate of reaction decreases as fewer reactions take place. Often increasing the substrate concentration can reverse these effects as the probability of the substrate binding is greater. Non-competitive inhibitors bind to other regions of the enzyme (ie not the active site). When they bind they change the shape of the enzyme altering the shape of the active site. The substrate can no longer bind to the active site so the rate of reaction decreases. The enzymes are inactive and so increasing the substrate concentration has no impact.