Why temperature affects enzymes

Collisions between all molecules increase as temperature increases. This is due to the increase in velocity and kinetic energy that follows temperature increases. With faster velocities, there will be less time between collisions. This results in more molecules reaching the activation energy, which increases the rate of the reactions. Since the molecules are also moving faster, collisions between enzymes and substrates also increase.

Thus the lower the kinetic energy, the lower the temperature of the system and, likewise, the higher the kinetic energy, the greater the temperature of the system. As the temperature of the system is increased, the internal energy of the molecules in the system will increase. The internal energy of the molecules may include the translational energy, vibrational energy and rotational energy of the molecules, the energy involved in chemical bonding of the molecules as well as the energy involved in nonbonding interactions.

Some of this heat may be converted into chemical potential energy. If this chemical potential energy increase is great enough some of the weak bonds that determine the three-dimensional shape of the active proteins may be broken. This could lead to thermal denaturation of the protein and thus inactivate the protein. Thus too much heat can cause the rate of an enzyme-catalyzed reaction to decrease because the enzyme or substrate becomes denatured and inactive. Each enzyme has a temperature range in which a maximal rate of reaction is achieved.

This maximum is known as the temperature optimum of the enzyme. PDF version of Introduction to Enzymes. Introduction to Enzymes Video. Place Order. Introduction to Enzymes The following has been excerpted from a very popular Worthington publication which was originally published in as the Manual of Clinical Enzyme Measurements. Temperature Effects Like most chemical reactions, the rate of an enzyme-catalyzed reaction increases as the temperature is raised.

An optimum activity is reached at the enzyme's optimum temperature. A continued increase in temperature results in a sharp decrease in activity as the enzyme's active site changes shape. It is now denatured. Each enzyme work bests at a specific pH value.

The optimum pH for an enzyme depends on where it normally works. For example, enzymes in the small intestine have an optimum pH of about 7.