Question

HCI present in the gastric juice helps in digestion by converting
A. Protein to renin
B. Pepsinogen to pepsin
C. Proteins to peptides
D. Both A and C

Answer 1

Hint: Gastric juice is a digestive fluid produced by the stomach, which is composed of HCI and certain other compounds and its functions include acting as a reservoir, acid secretion and enzyme secretion.

Complete Answer:
Let's have a look at the options to find the correct answer.

Option A: The conversion of protein to renin is not done by HCl present in the gastric juice. Renin is an aspartic protease protein, and an enzyme secreted by the kidney, which takes part in our body's renin - angiotensin - aldosterone system (RAAS) which mediates the volume of extracellular fluids. Therefore, this is the incorrect option.

Option B: HCl present in the gastric juice helps in the digestion by converting pepsinogen to the enzyme pepsin, which then proceeds the digestion by breaking the amino acid bonds, by a process known as proteolysis. Because of the presence of HCl, the highly acidic environment in the stomach causes denaturation of proteins or the loosening of their characteristic folded structure. Therefore, this is the correct option.

Option C: The conversion of proteins to peptides is not done by HCl in the gastric juice. Enzymes which convert proteins to peptides are called proteases. Examples for proteases are trypsin, pepsin etc. Proteases are also called proteolytic enzymes or proteinases. The process of breakdown of proteins to smaller polypeptides or amino acids is called proteolysis. Low pH or high temperature favours proteolysis. Therefore, this is the incorrect option.

Option D: Since HCl in gastric juice does not convert proteins to renin or proteins to peptides, this is the incorrect option.

Thus, the correct option is B) Pepsinogen to pepsin.

Note: Because of HCl, the acidic environment created in the stomach also helps in inhibition or destruction of many microorganisms, preventing infections. The pH of gastric juice is maintained at 1.5 to 3.5, with the help of HCl.