Question

Which one of the following does not digest milk with rennin?
A. Man
B. Frog
C. Rabbit
D. A calf

Answer 1

Hint: Chymosin is another name for rennin. The rennin is a proteolytic enzyme that is present in the stomach of mammals. It is very important for the digestion of milk in young ones. It helps in the curdling of milk.

Complete answer
Enzymes are the biological catalysts that carry out various biochemical reactions in the body. They help in the breakdown of substances into simpler products. They are very essential in a number of metabolic processes.
The stomach mainly helps in the digestion of proteins. It produces enzymes that help in the digestion of proteins. Rennin is a proteolytic enzyme (protein breakdown) that is produced by the chief cells of the stomach. It is present only in young mammals to help them in the digestion of mother's milk. Rennin is present in an inactive form in the stomach. The hydrochloric acid of the stomach converts it from prorenin into rennin.
After the birth of a child, the concentration or production of rennin increases to facilitate the digestion of milk proteins. In the presence of calcium present in milk, the rennin interacts with three of the four molecules present in the milk and coagulates it.
With time, the concentration of rennin decreases. The pepsin enzyme replaces rennin.
Mammals are animals that are characterized by the presence of mammary glands and body hairs. Examples of mammals are- humans, rabbits, cows etc.

Thus the answer of the above question is (B) Frog as it is an amphibian means it can live on both land and in water. No digestion of milk having rennin protein takes place in animals except mammals.

Note:
Digestion is the process in which complex substances that are present in food break into simpler ones. For example- the proteins are broken down to form amino acids. The nutrients obtained after the process of digestion are used for cell growth, energy production, cell repair etc.