Temperature, substrate concentration, and pH are three factors that can affect enzyme activity. Enzymes are catalysts -- substances that increase the rates of reactions. Without them, many essential processes, such as digestion, would occur too slowly for life to continue. Many enzymes have an optimal temperature and an optimal pH. The optimal temperature and optimal pH of an enzyme is the temperature and pH range in which the enzyme can work best without becoming inactive or denatured, a phenomenon that occurs when proteins start to unravel.
One of the main conditions that can affect enzyme activity is temperature. As heat increases, molecules usually start to move faster and faster, and this increased activity means that the molecules are more likely to collide with the enzyme. The higher collision rate allows the reaction rate to increase but only up to a certain point. Should the temperature increase too much, the enzyme’s protein can begin to denature, a potentially permanent process. The optimal temperature for many enzymes falls within a temperature range of 77-104°F (25-40°C), but some enzymes, for example those found within animals living in cold sea water or in hot springs, may have a higher or lower optimal temperature to allow them to do their work successfully.
Temperature is not the only factor that can affect enzyme activity. If the enzyme concentration remains the same, an increased concentration of substrate, which are the molecules involved in the reaction, can also affect how quickly an enzyme works. As substrate concentration increases, the rate of the reaction initially increases because there are more than enough enzymes to facilitate the reaction. After a certain point, however, the addition of more substrate does not affect enzyme activity because there are only so many enzymes available. Instead, the reaction rate will remain constant because the additional substrate has to wait for available enzymes to facilitate the reaction.
The pH level of a solution can also affect enzyme activity. Many enzymes can only work within a narrow pH range. If an enzyme finds itself in a hostile pH range, it could become denatured. The optimal pH for many enzymes is 7.0-7.5, but this is not always the case. Some enzymes, such as some in the human stomach, work best at an acidic pH of 1.5, while others, such as some found in the intestine, work best at a more alkaline pH of 8.0.
