Question

Explain the digestive processes taking place in the small intestine.

Answer 1

The small intestine is divisible into the initial short duodenum, the longer jejunum and the longest ileum. Food is moved forward into the duodenum due to peristaltic action. The pyloric sphincter in the stomach controls the movement of chyme. Hepatocytes produce bile in the liver. Bile is stored in the gall bladder and reaches duodenum through a bile duct. During emulsification, the bile salts convert large fats into smaller fat globules called the chylomicrons.

The pH of pancreatic juice is 7 to 8. It reaches the duodenum through a pancreatic duct. Water, minerals, trypsin, trypsinogen, enterokinase, chymotrypsinogen etc. are found in pancreatic juice.
Enzymatic reactions-
Proteins + Trypsin $\to$ Polypeptides + Peptones
Chymotrypsinogen + Enterokinase $\to$ Active Chymotrypsin
Chymotrypsin + Peptides of Phenylalanine, tryosine or tryptophan $\stackrel{hydrolysis}{\to }$ large peptides.
Carboxyl peptidase (exopeptidase) + Peptides (at the - COOH end) + Poly peptides $\to$ di, tri peptides + aminoacids
Lipase (triglycerides) $\stackrel{hydrolysis}{\to }$ free fatty acids + monoglycerides
Monoglycerides $\stackrel{hydrolysis}{\to }$ free fatty acids + glycerol.