Four factors that affect enzyme activity are:
To consider how these factors affect enzyme activity, it is important to know how to calculate the rates of a chemical reaction.
So to calculate the rate of an enzyme-catalysed reaction, we are measuring either the rate at which the substrate is used up or the rate at which the substrate is formed.
As the temperature increases, the rate of enzyme activity increases. Or in other words, as the temperature increases, the rate of reaction increases. A higher temperature results in higher kinetic energy. As the kinetic energy increases, there are more collisions between the enzymes and substrates.
However, this only happens up until an optimum point, which is the point at which enzymes are working at their fastest. At this point, there is the maximum frequency of collisions between the enzymes and substrates.
Once the temperature increases past the optimum, the rate of reaction decreases rapidly. Then the reaction will eventually stop as the temperature becomes too high.
At this point, the bonds that hold the enzyme together will begin to break, so the shape of the active site is altered. Therefore, the substrate can no longer bind with the enzyme and the enzyme is said to be denatured, which means it can no longer catalyse the reaction.
Most enzymes have an optimum pH of 7, which is neutral. However:
The bonds that hold the amino acid chains in the enzyme together are affected by the pH. If we make the pH more acidic or alkaline, then the enzyme activity drops to zero. This is because the shape of the active site has changed.
If the active site changes, then the substrate can no longer fit in the enzyme’s active site. So, the enzyme is denatured, meaning that it can no longer work.
In a fixed concentration of enzymes, as the substrate concentration increases, the rate of reaction will also increase.
However, this is up until a certain point. Eventually, the active sites of the enzymes will become occupied, which is the saturation point. After this point, the rate of reaction will remain constant, even if there is plenty of substrate remaining.
An optimum substrate concentration is needed for enzymes to work properly.
In a fixed concentration of substrate, as the enzyme concentration increases, the rate of reaction will also increase up to a particular point.
In this case, the concentration refers to the concentration of the substance binding to the enzyme. This is due to the fact that as the substrate concentration increases, the rate at which enzymes collide with substrates also increases. However, once all the substrate has been used up, the reaction will stop.