Question

Pepsin converts _________
A. Starch into sugar
B. Proteins into polypeptides
C. Proteins into amino acids
D. Fats into fatty acids

Answer 1

Hint: Pepsin is an enzyme that is present in the stomach of a person. The gastric chief cells secrete pepsin as an inactive enzyme that is called pepsinogen. It helps in the digestion of food that is done for energy.

Complete answer:
The process of digestion is accomplished by mechanical and chemical processes. Food digestion is the process of breakdown of large food particles into smaller absorbable nutrients that are needed for energy production, growth as well as cellular repair. It takes place in the gastrointestinal tract in two principal forms: mechanical and chemical.

The stomach plays a crucial role in the early stage of food digestion where it is stored for 4 to 5 hours. Apart from squeezing and churning the food bolus, it secretes a mixture of "gastric juices". Gastric juice comprises hydrochloric acid, water, mucous, pepsin as well as intrinsic factor. Out of the five pepsin is considered the principal enzyme that is involved in the digestion of proteins.

FUNCTION- Pepsin helps in the breakdown of proteins into smaller peptides and amino acids that get absorbed into the small intestine. It functions by the peptide chemical bonds that are found in them. In response to many stimuli, there are small basophilic cells that are present in the gastric glands, known as chief cells that produce pepsinogen.

ISSUES IN CONCERN- Pepsin depends on an acidic environment for the process of protein digestion to take place. It thus works in an acidic medium is approx. 1.5 to 2. Low pH helps pepsinogen to cleave itself to form an active protein. On reaching the duodenum, it becomes inactive as the pH reaches 6. Nonetheless, protein digestion continues to take place throughout the small intestine through the effects of many pancreatic enzymes like trypsin, chymotrypsin, elastase and carboxypeptidase. Protein digestion is an important function and it can take place at a pH of 8.

Thus the correct answer is option ‘B’.

Note: Stomach is the place that provides the ideal environment for the pepsin to operate for digestion of proteins. Doing so helps in breaking down proteins into smaller nutrients but at the same time puts the stomach at risk of autodigestion. Mucus lining loaded with bicarbonate helps to protect it from HCL and creates up a neutral pH environment that deactivates pepsin.