Question

Enzymes are proteins. Proteins are long chains of aminoacids linked to each other by peptide bonds. Aminoacids have many functional groups in their structure. These functional groups are, many of them at least, ionisable. As they are weak acids and bases in chemical nature, this ionization is influenced by pH of the solution. For many enzymes, activity is influenced by surrounding pH. This is depicted in the curve below, explain briefly.

Answer 1

Plot

Given here is a plot between pH (in the x-axis) and the enzyme activity (y-axis). The graph shows the change in the activity of an enzyme with change in the value of pH.
A bell-shaped curve is observed between enzyme activity and pH.

Enzyme activity at optimal pH

A peak is represented by a pH value at which the enzyme activity is maximum (the optimal pH).
This is due to the retention of proper structural configuration and conformation of the enzyme which renders proper functionality to it.

Enzyme activity beyond optimal pH

When the pH rises more than the optimum pH or drops down the optimum pH, the enzymatic activity decreases as is evident from the decline in the reaction velocity. This corresponds to either side of the maxima.

This is because changes in pH results in the changes in the charge of many amino acids present in the protein (enzyme). This leads to the formation of new bonds and breakage of older bonds present in the enzymes.

This results in the changing of the shape/ conformation of the enzyme and hence, affects enzyme activity.