Question

At which pH lysosomal enzymes remain active?
A. pH 5
B. pH 7
C. pH 8
D. pH 10

Answer 1

Lysosomes are organelles present in animal cells and are also commonly known as “suicide bags of the cell”. They have an internal acidic environment and are filled with hydrolytic enzymes.

Complete answer:
Lysosomes have almost 40 types of hydrolytic enzymes. Some of these enzymes are proteases, lipases, sulfatases and glycosidases. These enzymes help in the intracellular digestion of macromolecules.

Let us analyse the options to find the correct answer.
Option A: Lysosomal enzymes are acid hydrolases and are active at a pH of 5.0. Hence, this is the correct option. These enzymes remain active at acidic pH of 5.0 which is maintained in lysosomes by a vacuolar $H^+$ ATPase present in the lysosomal membrane. ATP is hydrolysed to pump $H^+$ ions into the lysosome which is responsible for maintaining the acidic pH in the lysosomes.

Option B: pH 7 provides a neutral environment and lysosomal enzymes are not active at this pH. Hence, this is an incorrect option.

Option C: pH 8 provides an alkaline or a basic environment and lysosomal enzymes are not active at this pH also. Hence, this is an incorrect option.

Option D: pH 10 also is an alkaline or a basic pH which is again not an optimal pH for lysosomal enzymes. Hence this is an incorrect option.

Thus, the correct option is A) pH 5.

Note: pH is short for power of hydrogen. A pH scale of 1-14 is used to denote the acidity or basicity of an aqueous solution with pH 1 being the most acidic and pH 14 being the most basic or alkaline.