Digestion and Absorption in the Small Intestine
Most of the chemical digestions happen in the duodenum. This affects all four categories of macromolecules and what makes them up. Enzymatic digestion of macromolecules occurs by carbohydrases, lipases, proteases, and nucleases.
Carbohydrate Digestion and Absorption (Carbohydrases)
This process starts in the mouth with saliva but most of the process happens in the stomach. When it enters the stomach, hydrolchloric acid makes the acid in the stomach a PH of 2. Digestions of carbohydrates (like the bread in the sandwich) does not occur until the food has made it to the small intestine where the PH is 8.This turns the carbohydrates into disaccharides which can sometimes be hydrolyzed into monosaccharides: glucose and fructose. These monosaccharides are absorbed by active transport into the intestinal villi where they enter the bloodstream and are transported to the liver. Some glucose is stored for later use as glycogen.
Protein Digestion and Absorption (Proteases)
The polypeptides are produced in the stomach by pepsin and are digested by the small intestine by two proteases called trypsin and chymotrypsin which are inactive enzymes. However, they are activated by an enzyme in the small intestine. Proteins are broken down by peptidases (which produce amino acids) and
nucleosidases (which makes a product of sugars and phosphates).They hydrolyze peptide bonds resulting in peptide chains. Enzymes in the small intestine allow for the splitting of the peptide chains into single amino acid cells. They are carried directly to the liver and combine with CO2 which leads to the formation of waste and is left through the anus. Other amino acids (from the meat) are released into body cells and are used to make proteins.
nucleosidases (which makes a product of sugars and phosphates).They hydrolyze peptide bonds resulting in peptide chains. Enzymes in the small intestine allow for the splitting of the peptide chains into single amino acid cells. They are carried directly to the liver and combine with CO2 which leads to the formation of waste and is left through the anus. Other amino acids (from the meat) are released into body cells and are used to make proteins.
Fat Digestion and Absorption (Lipases)
When fats arrive in the duodenum, bile is created. It emulsifies the fat droplets using a physical process. The breakdown of fats by hydrolysis are absorbed into the cells of the villi by simple diffusion. They are then reassembled into triglycerides and coated with proteins to make them soluble before they enter the lymph vessels. The lymph vessels carry these to the chest where they join the bloodstream. They are hydrolyzed making free fatty acids and glycerol available for cells.
Nucleic Acid Digestion and Absorption (Nucleases)
In the small intestines nucleic acids are digested by enzymes called nucleases to make nucleotides. Nucleotides are hydrolyzed to their bases and sugars and phosphates to be absorbed into the bloodstream and cells through active transport.