A cell’s physical and chemical environment affects enzyme activity. The activity of an enzyme is affected by general environmental conditions, such as temperature and pH. Each enzyme works best at certain optimal conditions, which favor the most active conformation for the enzyme molecule. Temperature has a major impact on reaction rate. As temperature increases, collisions between substrates and active sites occur more frequently as molecules move more rapidly. As temperature increases further, thermal agitation begins to disrupt the weak bonds that stabilize the protein’s active conformation, and the protein denatures. Each enzyme has an optimal temperature. Most human enzymes have optimal temperatures of about 35–40°C. Bacteria that live in hot springs contain enzymes with optimal temperatures of 70°C or above. Each enzyme also has an optimal pH.
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