factors that affect enzyme reactions


Factors that affect enzyme reactivity


The pH of a solution is a measure of its hydrogen ion concentration. each enzyme has an optimum pH, that pH is the concentration the enzyme works fastest at. The pH of a solution is calculated using the formula pH=-log10[H+]. A hydrogen ion (H+) concentration of 1X10-9 therefore has a pH of 9. In a similar way to a chnage in temperature affecting the rate of ezyme action,  a change in pH away from the optimum affects the rate of enzyme action. An increase or decrease in pH reduces the rate of enxyme action. If the change in pH is more extreme then, beyond a certain pH, enxyme becomes denatured.

The pH affects how an enzyme works in many ways;

-A change in pH alters the charges on the amino acids that make up the active site of the enzyme. As a result, the substrate can no longer become attached to the active site and so the enzyme-substrate complex cannot be formed.

-Depending on how signifcant the change in pH is, it may cause the bonds maintaining the enzyme's tertiary structure to break. The active site therefore changes shape.

The arrangment of the ctive site determined by the hydrogen and ionic bonds between -NH2 and -COOH groups of the plypeptides that make up the enzyme. The change in H+ ions affects this bonding, causing the active site to change shape.

It is important to note that pH fluctutions inside organisms are usually small, this means they are far more likely to reduce an enzyme's activity than to denature it.


A rise in temperature increases the kinetic energy of molecules. As a result, the molecules move around more rapidly and collide with each other more often. In an enzyme-catalysed reaction, this means that the enzymes and substrate molecules come together more often in a given time. There are more effective collisions resulting in more enxyme-substrate complexes being formed and so the rate of reaction increases.

Shown on a graph, this gives a rising curve. However, the temperature rise also begins to cause the hydrogen and other bonds in the enzyme molecule to break. This results in the enzyme, including its active site, changing shape. At first, the substrate fits less easily into thsi changed active site, slowing the rate of reaction. For…


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