In human digestion, pepsin is an enzyme present in gastric juice. Pepsin mainly helps in the digestion of which class of food?

Introduction / Context:

Digestive enzymes are specialised proteins that help break down complex food molecules into simpler forms that the body can absorb. Each enzyme works best on a particular type of nutrient, such as proteins, carbohydrates, or fats. Pepsin is one of the most important enzymes in gastric juice and is often mentioned in school biology when describing the role of the stomach. This question tests whether learners can correctly associate pepsin with the type of food it digests.

Given Data / Assumptions:

• The enzyme mentioned is pepsin.
• Pepsin is known to be present in the acidic environment of the stomach.
• Options cover different food groups such as proteins, carbohydrates, fats, and vitamins.
• We assume normal human digestive physiology and standard school textbook descriptions.

Concept / Approach:

Pepsin is a proteolytic enzyme, which means it breaks down proteins. It is secreted in an inactive form called pepsinogen by cells in the stomach wall and is activated by hydrochloric acid present in gastric juice. Once activated, pepsin begins the digestion of proteins by breaking them into smaller polypeptides. Carbohydrates like starch start to be digested in the mouth by salivary amylase, and fats are mainly digested in the small intestine by pancreatic lipase with the help of bile. Vitamins do not require digestion; they are absorbed in relatively simple forms. Therefore, pepsin is correctly associated with protein digestion.

Step-by-Step Solution:

Step 1: Identify pepsin as an enzyme produced in the stomach as part of gastric juice. Step 2: Recall that pepsin belongs to the group of proteases, enzymes that act on proteins. Step 3: Remember that pepsin breaks large protein molecules into smaller peptide chains in acidic conditions. Step 4: Compare this role with the digestion of carbohydrates and fats, which mainly takes place in other parts of the digestive tract. Step 5: Choose proteins as the food group digested by pepsin.

Verification / Alternative check:

Digestive system charts in biology textbooks summarise the action of enzymes by organ. Under stomach, they list pepsin and note that it acts on proteins. In contrast, salivary amylase and pancreatic amylase are shown acting on starch, and lipase is tied to fat digestion in the intestine. Clinical discussions of peptic ulcers and protein digestion also mention pepsin as the main gastric protease enzyme. These sources consistently confirm the link between pepsin and proteins.

Why Other Options Are Wrong:

Option B, Starch, is wrong because starch is primarily digested by amylases in the mouth and small intestine, not by pepsin in the stomach. Option C, Carbohydrates other than starch, are handled by other enzymes and do not rely on pepsin. Option D, Fats and oils, are mainly emulsified by bile and then digested by lipase in the small intestine. Option E, Vitamins, are not digested by pepsin or other enzymes; they are absorbed in their basic forms. Therefore, none of these options accurately describe the function of pepsin.

Common Pitfalls:

Students sometimes confuse the roles of different digestive enzymes and may think every enzyme in the stomach works on all food types. Others may misremember that because gastric juice is strongly acidic, it helps digest fats or starch directly. To avoid such errors, learners should memorise simple associations, for example: pepsin with proteins, amylase with starch, and lipase with fats. Creating a small table of enzymes, locations, and substrates during revision is a useful strategy.

Final Answer:

Pepsin is an enzyme that primarily digests proteins.