Question

Intracellular digestion occurs in human body for
1. Lipids
2. Proteins
3. Sucrose
4. All of the above

Answer 1

Hint: Intracellular digestion is a type of digestion in which the digestion of the food material occurs inside the cell. The lysosomes are responsible for the intracellular digestion.

Complete answer:
The intracellular digestion in the human body occurs for Lipids, Proteins and Carbohydrates (sucrose).

The proteins are formed by the long chains of amino acids and bound together by peptide linkage. The proteins are broken down into amino acids by gastro intestinal enzymes. The enzymes which help in the digestion of proteins are called proteases or peptidases. Most of the proteases are secreted in active form called proenzymes and most of the proenzymes are activated at their site of action by specific proteases or by change in pH. As saliva has no proteolytic enzymes, so protein digestion does not take place in the mouth, it starts in the stomach.

Sucrose is a type of carbohydrates and the digestion of carbohydrates occurs in the mouth because the gastric juice and bile juice does not contain any carbohydrate digestive enzymes. The enzyme ptyalin secreted by parotid glands present in the salivary amylase. The carbohydrates are hydrolyzed by ptyalin into simpler forms (maltose).

Lipids are digested by the enzyme lipases and these enzymes are water soluble and secreted in aqueous digestive juices. Majority of lipid digestion occurs in the small intestine due to the presence of pancreatic lipases. These enzymes break down lipids into fatty acids and glycerol.

So the correct answer is option D.

Note: There are some hydrolytic enzymes present in the gastric juice that destroy the ptyalin within a short period of time. The human diet also contains some amount of cellulose but there are no enzymes present in the human body which hydrolyze the cellulose.