Carbohydrates, proteins, and fats are digested through a series of enzymatic reactions and absorption processes primarily in the small intestine. Carbohydrates are broken down into simple sugars, proteins into amino acids, and fats into fatty acids and glycerol.
Carbohydrates:
Mouth: Salivary amylase in saliva begins the breakdown of starch into maltose.
Small Intestine: Pancreatic amylase and other enzymes in the small intestine further break down carbohydrates into monosaccharides like glucose, fructose, and galactose.
Absorption: These simple sugars are then absorbed into the bloodstream for transport to cells for energy or storage.
Proteins:
Stomach:
Hydrochloric acid and pepsin in the stomach initiate protein digestion, breaking down proteins into smaller peptides.
Small Intestine:
Pancreatic proteases (like trypsin and chymotrypsin) and other enzymes in the small intestine continue breaking down proteins into amino acids.
Absorption:
Amino acids are then absorbed into the bloodstream for use in building new proteins and other cellular processes.
Fats:
Small Intestine:
Bile salts from the liver emulsify fats, breaking them into smaller droplets, and pancreatic lipase digests fats into fatty acids and monoglycerides.
Absorption:
Fatty acids and monoglycerides are absorbed into the intestinal cells, where they are reassembled into triglycerides and packaged into chylomicrons.
Transport:
Chylomicrons enter the lymphatic system and eventually reach the bloodstream for transport to various tissues.