The three-dimensional structure of an enzyme has many different crevices which will only allow certain substrates to join. Just like a lock and key, there must be a perfect fit between the enzyme and substrate for the reaction to occur. Once this combination occurs, the biological reaction will be able to take place at an extremely higher rate. The forces which maintain the shape of the enzyme include salt bridges, hydrogen bonds, disulfide bonds, and hydrophobic interactions. Any chemicals or temperature changes can alter these forces within the enzyme, and limit the ability of the enzyme to catalyze a reaction.
Heat denatures all enzymes.
The effects of ion concentration and pH on the activity of an enzyme depend on the particular enzyme. Many enzymes are also affected my chemicals known as inhibitors. There are two types of inhibitors, competitive inhibitors, which occupy the active site on the enzyme blocking the substrate, and noncompetitive inhibitors which bind at some other site in the enzyme causing a conformational change near the active site. Both types denature the enzyme and therefore limit its usefulness and power. In this experiment, catalysis of the decomposition of hydrogen peroxide will be studied with the use of a potato extract.