Concept:Protein digestion begins in the stomach due to the action of pepsin.
Explanation:The stomach secretes gastric juice containing hydrochloric acid (
HCl) and pepsinogen.
In the acidic environment, pepsinogen is converted into the active enzyme pepsin.
Pepsin breaks down large protein molecules into smaller peptides.
This is the first step of protein digestion.
The small intestine continues the process, but the digestion of proteins starts in the stomach.
The mouth is not involved in protein digestion, and the large intestine mainly absorbs water.
Answer:B. stomach