Enzymes are protein molecules essential to all living systems in regulating and increasing the rates of chemical reactions to produce specific products. Maintaining the correct balance of enzymes in a living system is vital to its health and reduces the system's need for energy. The activity of these specialised biological catalysts is affected by the temperature of the environment.
Lower temperatures mean that molecules in a living system are moving more slowly and have lower kinetic energy. Molecules must collide for reactions to occur, so if the temperature is too low and particles are moving slowly, the chance for an enzyme molecule to collide with its substrate (the specific chemical it can react with) is much lower. The temperature at which an enzyme begins to react is called "activation energy." At low temperatures, enzyme reactions occur more slowly, and if the temperature is too low, reactions may not happen at all.
Higher temperatures in a living system mean that the chance for activation energy to be reached is increased because the kinetic energy of the system is greater. Greater kinetic energy means more collisions are possible between enzymes and substrates, and the rate of an enzyme's reaction increases. At very high temperatures enzymes can "denature," which means the heat causes them to lose their original shape necessary for them to react. Therefore, if temperatures are too high, a decrease in reaction rate occurs as a result of the enzymes denaturing.
The temperature at which the maximum rate of an enzyme's reaction occurs is called the "temperature optimum" of the enzyme, and every enzyme has a different temperature optimum. Living systems are adapted to their environments; an Alaskan shrimp will endure much colder temperatures than bacteria living in the geyser of a hot spring. The geyser's bacteria could not exist easily in the cold Alaskan seas because not only would its enzymes never reach their temperature optimum, but the enzymes may never reach their activation energy. Conversely, the Alaskan shrimp would not do very well living in the hot springs because their enzymes would probably denature and cease to react. An experiment to examine how temperature affects enzyme activity is in the resources.
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