Concept:Enzymatic digestion of proteins starts in the stomach.
Explanation:The part labelled I is the stomach.
Protein digestion is the chemical breakdown of protein molecules by enzymes.
This process begins in the stomach, not in the pancreas, liver, or gall bladder.
The stomach wall has chief cells that secrete an inactive enzyme called pepsinogen.
Parietal cells in the stomach release hydrochloric acid (
HCl).
The acid converts pepsinogen into the active enzyme pepsin.
Pepsin then starts breaking large protein molecules into smaller chains called polypeptides.
Thus, the labelled part where enzymatic digestion of protein begins is part I.
Answer:A. I
