Question

Explain the effect of pH on enzymes.

Answer 1

Enzymes are substances produced inside the body of living organisms that act as a catalyst for biochemical reactions. Enzymes are not consumed during biochemical reactions; hence they remain unaltered after reaction.

Complete answer:
• pH is used to show how many hydrogen ions or hydroxides are present in a sample. pH of a sample is dependent on its alkaline or acidic nature. pH of a sample can be measured using pH scale. An acid has a low pH (less than 7), while an alkali has a high pH (more than 7). A sample having pH of 7 is considered neutral.
• As the pH of a sample changes, it causes a number of changes in the sample. For example a change in pH can cause ionization of amino acids or molecules, and changes in structure and shape of proteins (conformational and structural changes). These changes affect the activities of proteins. Thus change in pH also affects the enzyme activity as enzymes are also proteins.
• Each enzyme has a particular pH value or pH range within which it can perform at its best i.e. ideal pH for an enzyme to work. This pH is called optimum pH or optimal pH. Optimum pH value differs from enzyme to enzyme.

The optimum pH value or range of some common enzymes are given in following table:

Enzyme	Optimum pH
Pepsin	1.5 to 1.6
Trypsin	7.8 to 8.7
Urease	7
Pancreatic Lipase	8
Gastric Lipase	4 to 5

Note: For most of the enzymes, very high or very low pH is not suitable. Extreme pH can destroy the enzymes making them inactive. Most of the enzymes work in neutral pH conditions except some digestive enzymes. Digestive enzymes like pepsin and trypsin work in acidic and alkaline pH environments respectively. Similar to pH, the activity of enzyme is also affected by other factors like temperature and concentration of enzyme and substrates.