Question

Chief function of HCl is
A. To maintain a low pH to promote the growth of microorganism
B. To facilitate absorption
C. To maintain low pH to activate pepsinogen to form pepsin
D. To dissolve enzyme secreted in the stomach

Answer 1

Hint: The breakdown of the peptide bonds in our stomach requires a highly acidic environment.

Complete answer:
The mucosal glands present in the stomach secretes a thin serous gastric acid or gastric juice. The gastric juice consists of HCl; electrolytes like sodium chloride, and potassium chloride; digestive enzymes like amylase, pepsinogen, and lipase; intrinsic factors; water; and mucus. Our stomach secretes about 1.5 liters of gastric juice per day.
> HCl- The hydrochloric acid is the major constituent of gastric secretion and is secreted by the ‘Parietal cells'. It maintains the acidic pH of the stomach which is essential for the conversion of inactivated pepsinogen to active pepsin. HCl also results in denaturation of protein structure which makes it liable to digestion. It also kills the harmful pathogens thriving in the stomach.
> Na+ and K+ present as sodium and potassium chloride in the secretion maintain a favorable pH and ionic potential of the gastric acid.
> Pepsinogen- It is secreted by the chief or peptic cells and is responsible for the breakdown of proteins.
> Gastric amylase- It is not secreted by gastric glands. In fact, it is the secretion of the salivary gland that has reached the stomach. It actively participates in the breakdown of carbohydrates but remains inactivated in the acidic environment of the stomach.
> Gastric lipase- It is secreted by the oxyntic or parietal cells and helps in the breakdown of fats.
> Castle intrinsic factor- It helps in the absorption of Vitamin B 12 and Folic acid.
> Mucus- It is secreted by mucous neck cells and prevents the gastric epithelium from erosion by highly acidic HCl.

So, the correct answer is ‘To maintain low pH to activate pepsinogen to form pepsin’.

Note:
- The role of gastric juice in digestion was first established by William Beaumont and Alexis Martin.
- The acidic environment in the duodenum is neutralized by sodium bicarbonate which is compulsory for the activity of pancreatic amylase.
- The pH of the stomach ranges from 2-2.5.
- The regurgitation of the acidic content of the stomach into the esophagus leads to heartburn or cardiac achalasia.