This video explains how changes in temperature, changes in pH and the presence of chemical inhibitors can affect enzyme activity. Low temperatures slow enzymes and substrates down which reduces collisions between them. High temperatures and changes in pH change the shape of (denature) enzymes. Competitive inhibitors compete with the substrate and block the active site and non-competitive inhibitors bind at an alternative site on the enzyme which causes the enzyme to change shape so that the substrate can no longer bind to the active site. For more Biology video lessons check out www.anytimeeducation.com