Question

The initial step in the digestion of milk in humans is carried out by which of the given enzymes?
A. Lipases
B. Trypsin
C. Rennin
D. Pepsin

Answer 1

Hint: The digestion of carbohydrates starts for the mouth or oral cavity by the enzyme amylase likewise, the digestion of milk which is a protein (casein) starts from the stomach by the specific enzyme. A special enzyme is also present in younger ones for the digestion of milk.

Complete answer: Here, we are asked about the enzyme that helps in the initial digestion of the milk in humans. We know milk is rich in protein and thus for the digestion of proteins, a protein-digesting enzyme can only work.
So, the lipase enzyme can be eliminated as it helps in the breakdown of fats. Now, we are left with the trypsin, renin, and pepsin. All these three enzymes are proteolytic enzymes.
Trypsin has high specificity and acts only on the lysine and arginine amino acid residue. Since trypsin is secreted by the pancreas and the milk is digested in the stomach so trypsin can not be the right answer.
Moreover, we are asked about the enzyme that helps in the initial digestion of the milk in humans. In humans, it is pepsin that helps in the initial digestion whereas in calves or animals it is rennin.
Therefore, the correct answer is Option D-Pepsin

Note: Remember, we are asked about the enzyme in humans and the answer will differ from humans to calves. Since both of these organisms have a different type of proteolytic enzyme for milk digestion. In humans and calves, it is pepsin and rennin respectively that helps in the milk digestion.