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Enzymes and temperature can work together to allow certain, necessary reactions to take place quicker than they would without the presence of enzymes. As the temperature increases, the enzymes and substrates — the name given to reactants in an enzyme reaction — collide more frequently so the enzymes have more opportunity to catalyze reactions. This phenomenon increases until optimum temperature is reached. Further increase in temperature will denature enzymes and render them useless for catalyzing reactions. At a low temperature, there is not enough energy for reactions to take place, and the enzymes are not able to do their work.
For a reaction to take place, reactants must collide with enough energy for them to break bonds and create new ones. This is called the activation energy. While an enzyme reduces the amount of activation energy needed for a reaction to take place, a certain amount of energy is still needed. Kinetic energy, the energy a molecule has because of its motion, can increase with the increase of temperature. This is one of the main reasons there is a connection between enzymes and temperature.
As temperature increases, the enzymes and substrates collide and interact more and more. This means that as temperature increases, an enzyme reaction occurs faster. In fact, the increase in activity of the enzymes and temperature increase have an almost linear correlation. This phenomenon continues until optimum temperature is reached for the enzyme. At this temperature, the enzyme reaction is proceeding as quickly as it can.
Most enzymes have their optimal temperature somewhere between 32 to 104°F (0 to 40°C). Once the temperature rises beyond optimal, the connection between enzymes and temperature changes because enzymes start to denature — the bonds that hold the enzyme into shape begin to break. When this happens, the activation sites the substrates use no longer exist in the correct shape, and substrates cannot fit into them. It is possible for enzymes to survive higher than optimal temperatures, but this usually happens only if they are exposed to this higher temperature for a short period.
A connection between enzymes and temperature also exists when it comes to lower temperatures. With low temperatures, the substrates and enzymes do not have much kinetic energy. Even if they collide, there may not be enough energy for the reaction to take place. Thus, at a relatively low temperature, enzymes are not able to do their work. This is one of the reasons the human body strives to keep within a certain temperature: too hot and proteins, including enzymes, denature; too cold and enzyme reactions take place too slowly.