CBSE Class 11-science Answered

Digestion of proteins:

• Pepsinogen is converted into pepsin.
• Pepsin hydrolyses proteins into proteoses and peptones (peptides).

• Trypsin, chymotrypsin and carboxypeptidase present in the pancreatic juice act on the partially digested proteins from the stomach (proteins, peptones, proteoses) into dipeptides.

• Dipeptidases (Enzymes present in the intestinal juice) act on dipeptides and break them down into amino acids.

In buccal cavity:

• Saliva secreted into the buccal cavity contains electrolytes such as Na⁺, K⁺, Cl^-,  enzymes such as salivary amylase and lysozyme.
• Hydrolytic action of salivary amylase hydrolyses the starch into maltose.

In small intestine:

• Pancreatic amylase present in the pancreatic juice hydrolyses remaining carbohydrates into disaccharides.

• Diasccharidases (enzymes present in the intestinal juice) such as maltase, sucrase, lactase breakdown disaccharides into monosaccharides such as glucose, maltose, fructose, etc.

Digestion of fats:

In stomach:

• Gastric lipases are secreted in very small amount. They bring about mild hydrolysis of fats into fatty acids and glycerol.

In small intestine:

• Bile breaks down large lipid molecules into small micelles of fats. This process is called emulsification. Emulsification makes the further digestion of fats by lipases easy.
• Pancreatic lipases break down fat micelles into diglycerides first and then monoglycerides.

• Intestinal lipases acts on monoglycerides and break them down into fatty acids and glycerol.