Question

Discuss the digestion of carbohydrates and proteins in the alimentary canal.

Answer 1

• The digestion of the proteins begin in the stomach where it is acted upon by the proteolytic enzyme of the stomach, pepsin. Pepsin converts proteins into proteoses and peptones (peptides). Proteins, proteoses and peptons in the chyme reaching the intestine are acted upon by the proteolytic enzymes (trypsin, chemotrypsin, carboxypeptidases) of the pancreatic juice and are converted into dipeptides. The enzymes in the succus entericus acts on the end product of the above reaction to form the simple absorbable forms. Dipeptidases present in the succus entericus converts the dipeptides into amino acids. Amino acids thus formed are absorbed in the jejunum and ileum regions of the small intestine.
  
• The digestion of carbohydrates begins in the mouth where the starch present in the food is acted upon by the salivary amylase which converts it into maltose. About 30% of starch is hydrolyzed in the mouth. No significant digestion of carbohydrates occurs in stomach. Pancreatic amylase found in pancreatic juice acts on the carbohydrates and converts it into disaccharides. The enzymes of succus entericus acts on the end products of the above reaction. Maltose is converted into glucose + glucose by action of maltase. Lactose into glucose and galactose by action of lactase and Sucrose into glucose and fructose by sucrase present in succus entericus. The products thus formed are simple and are absorbed in the jejunum and ileum regions of intestine.