Question

Describe the process of digestion of proteins in the stomach.

Answer 1

Hint: The digestion of proteins in the human body starts in the stomach where protein digesting enzymes and appropriate medium is present.

Complete answer:
1. The digestion of food is the conversion of complex food particles into the simpler ones for their easier absorption and utilization by the body. 

2. Food is first ingested through the buccal cavity or mouth where a carbohydrate digesting enzyme called salivary amylase is present which breaks down the complex carbohydrate onto disaccharide called maltose. 

3. The food then, from the buccal cavity reaches the stomach through the esophagus by peristaltic movement. No digestion takes place in the esophagus.
4. Then the digestion of proteins starts in the stomach only and thus stomach is also known as a site for protein digestion. 

5. Gastric glands are present in the lining of the stomach which are known to produce three secretions:
> Hydrochloric acid
> Mucous which lines the stomach and protect it from acidic nature of Hydrochloric acid
> Protein digesting enzyme called as Pepsin in its proactive form
6. The digestion of proteins is initiated by the enzyme Pepsin in the stomach. It is present in a pro-enzyme proactive form called pepsinogen which gets converted to pepsin in the presence of hydrochloric acid which is secreted by gastric glands in the stomach. 

7. The pepsin breaks the protein into small chains of proteases and peptones. These chains then reach to the small intestine where other protein digesting enzymes are present and further digestion of proteins takes place.

8. Other protein digesting enzymes called trypsin are secreted by pancreas in pancreatic juice which reaches the small intestine. Pancreatic juice also contains enzymes like lipase for fat digestion and amylase for carbohydrate digestion.

9. At last, protein gets converted into amino acids, carbohydrates get converted into glucose and fats get converted into fatty acids and glycerol.

Note: The enzyme pepsin responsible for protein digestion in the stomach can be confused with other digestive enzymes like amylase, trypsin, lipase which are present in the small intestine.