What is the role of small intestine in digestive system proteins and fats?

1. Proteins:

The small intestine plays a crucial role in digesting proteins and breaking them down into amino acids, which can then be absorbed and used by the body. The process of protein digestion in the small intestine involves several steps:

- Mechanical digestion: The muscular walls of the small intestine contract and relax, physically breaking down the food into smaller pieces, increasing the surface area for enzymatic action.

- Chemical digestion: The pancreas releases enzymes called proteases, which break down proteins into smaller peptides. Two important proteases are trypsin and chymotrypsin. Trypsin primarily digests proteins in the alkaline environment of the small intestine, while chymotrypsin works best in slightly acidic conditions.

- Absorption: Once the proteins are broken down into peptides, they are further degraded by enzymes called peptidases, which are produced by the brush border cells lining the small intestine. These peptidases break the peptides into individual amino acids. The amino acids are then actively transported across the intestinal wall into the bloodstream.

2. Fats:

The small intestine also plays a vital role in digesting fats and breaking them down into fatty acids and glycerol, which can be absorbed and used by the body. The process of fat digestion involves the following steps:

- Emulsification: Fats are insoluble in water, so the first step in fat digestion is to emulsify them. The gallbladder releases bile salts into the small intestine, which help break down fats into smaller droplets, increasing the surface area for enzymatic action.

- Chemical digestion: The pancreas releases enzymes called lipases that break down fats into fatty acids and glycerol. The main lipase involved in fat digestion is pancreatic lipase. It works in conjunction with bile salts to hydrolyze triglycerides (the main form of dietary fats) into free fatty acids and monoglycerides.

- Absorption: Once the fats are broken down into fatty acids and glycerol, they are absorbed into the intestinal wall. The fatty acids are absorbed into the lymphatic system, while the glycerol is absorbed into the bloodstream.