Question

Rennin acts on milk proteins and converts?
A) Caseinogen to casein
B) Casein to paracasein
C) Caseinogen into paracasein
D) Paracasein into caseinogen

Answer 1

Hint: Enzymes are the proteins which act as catalysts i.e. speed up the biological reaction in the human body. There are many digestive enzymes like amylase, trypsin, and chymotrypsin which are responsible for the digestion of food.

Complete answer:
Proteolytic enzymes are the group of enzymes that break down the proteins into shorter fragments or amino acids. Rennin or chymosin is the digestive enzyme found in newborn ruminant animals like calves for the digestion of milk.

Option A: The rennin is found in infant calves which help in the digestion of milk. The rennin helps in curdling the milk by converting the caseinogen into the insoluble form of casein. This ensures that the milk remains in the stomach for a long period of time Therefore this is the correct option.

Option B: Insoluble casein is converted into paracasein in the presence of calcium. The casein breaks down into the two molecules of paracasein after which it cannot be further broken
down. Therefore this is also a correct option.

Option C: Caseinogen is not directly converted into paracasein in presence of rennin. It is a multistep process. Therefore this is an incorrect option.

Option D: The rennin cannot convert paracasein into caseinogen i.e. this is not a reversible reaction. Therefore this is an incorrect option.

Thus, the correct option is B) Casein to paracasein.

Note: Rennet is the commercial form of rennin and this form of rennin is used for cheese production. Humans have a pseudogene for rennin but it does not produce any enzyme. Humans have pepsin and lipase to digest milk instead of rennin.