1.6 Enzymes (part 2)
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The function of enzymes is affected by temperature and pH.
Temperature
Enzymes in the human body have evolved to work best at body temperature, which is 37°C. At this temperature the rate of reaction is at its greatest, and we say that the enzymes optimal temperature is 37°C. A temperature above or below 37°C results in a lower rate of reaction.
Enzymes in the human body have evolved to work best at body temperature, which is 37°C. At this temperature the rate of reaction is at its greatest, and we say that the enzymes optimal temperature is 37°C. A temperature above or below 37°C results in a lower rate of reaction.
Let’s start from 0°C and start increasing our temperature and see what happens to the rate of reaction. As we increase the temperature from 0°C, the rate of reaction increases. This is because the molecules in the enzyme and the substrate have more energy. As they both have more energy, the likelihood of them colliding increases and so does the rate of reaction. The rate of reaction will continue increasing until the optimal temperature (37°C).
When the temperature rises above 37°C, the proteins that the enzymes are made up of start to break down because of the excessive heat. This process is known as denaturing and usually starts to occur when the temperature exceeds 40°C. We can see from the graph that the fall down in the rate of reaction is quite significant when the temperature rises above 40°C.
When the temperature rises above 37°C, the proteins that the enzymes are made up of start to break down because of the excessive heat. This process is known as denaturing and usually starts to occur when the temperature exceeds 40°C. We can see from the graph that the fall down in the rate of reaction is quite significant when the temperature rises above 40°C.
pH
In addition to temperature, enzymes are also affected by pH. Enzymes have evolved to work best at the pH level of the cell that they are operating in, which is usually neutral (pH of 7).
In addition to temperature, enzymes are also affected by pH. Enzymes have evolved to work best at the pH level of the cell that they are operating in, which is usually neutral (pH of 7).
If the pH level is above or below this, the rate of reaction falls. The rate of reaction falls because the pH interferes with the bonds holding the enzyme together. The pH where enzymes work best is known as the optimal pH. For most enzymes, the optimal pH is 7. However, the optimal pH depends on what cell the enzyme is in. For example, the stomach produces an enzyme called pepsin. The stomach produces hydrochloric acid, which makes the contents of the stomach very acidic. The enzyme pepsin has evolved to work at an optimal pH of 2, which is the pH of the stomach.