How do cells regulate the activity of enzymes?

Cells regulate enzyme activity through two methods: allosteric inhibition and competitive inhibition. Allosteric inhibition is when something (an ion, an organic chemical, etc..) bonds to a site on the enzyme (not on the active site), and changes the shape of the enzyme. Competitive inhibition is when something (an ion, an organic chemical, etc..) enters the active site so that the true substrate can not enter into the enzyme to have a reaction.