In human body, the digestion of protein begins in which of the following organs?

1. A

   Liver

   (a) Liver. The liver makes bile for fat emulsification; it is not where protein digestion begins.

2. B

   Mouth

   (b) Mouth. Salivary amylase starts starch digestion; pepsin is absent in saliva, so protein does not begin here.

3. C

   Small intestine

   (c) Small intestine. Trypsin and chymotrypsin continue protein digestion, but they do not start it.

4. D

   Stomach

   (d) Stomach. Gastric pepsin (from pepsinogen plus HCl) begins protein digestion in the stomach. That organ is the official key.

Summary. Official key is (d). Protein digestion begins in the stomach with pepsin. The mouth starts starch, the liver makes bile, the small intestine continues proteins.