Digestion and Absorption

SYNOPSIS

• Conversion of complex food substances to simple absorbable substances is called digestion.
  
  
• Human Digestive System
  
  
  
  
• Summary of Chemical Digestion
  
  
  

  Part of the Alimentary Canal	Digestive Juices/Enzymes	Source of Secretion	Food Digested	End-product
  Mouth	Saliva
  	Salivary amylase	Salivary glands	Polysaccharides (Starch)	Disaccharides (Maltose)
  Oesophagus	-	-	-	-
  Stomach	Gastric juice
  	HCl	Gastric glands	-	Converts pepsinogen and prorennin to the corresponding active forms pepsin and rennin Provides an acidic environment Kills bacteria in food
  	Pepsin	Gastric glands	Proteins	Proteoses, peptones
  	Rennin (found in infants and young children)	Gastric glands	Casein	Proteoses, peptones
  	Gastric lipase	Gastric glands	Fats (emulsification)	Fatty acids and glycerol
  Small Intestine (Duodenum)	Bile
  	Bile (bilirubin + biliverdin + cholesterol + phospholipids + bile salts) No enzymes	Liver (stored in the gall bladder)	Fats	Emulsifies fats into micelles
  	Pancreatic juice
  	Trypsin, chymotrypsin, carboxypeptidase	Pancreas	Proteins, peptones, proteoses	Dipeptides
  	Amylase	Pancreas	Polysaccharides	Disaccharides
  	Lipase	Pancreas	Fats	Diglycerides, monoglycerides
  	Nucleases	Pancreas	Nucleic acids	Nucleotides
  	Succus entericus
  	Disaccharidases  (Example: Maltase)	Intestinal glands	Disaccharides (Example: Maltose)	Monosaccharides (Example: Glucose)
  	Dipeptidases	Intestinal glands	Dipeptides	Amino acids
  	Lipases	Intestinal glands	Monoglycerides	Fatty acids and glycerol
  	Nucleases	Intestinal glands	Nucleotides	Nucleosides
  	Nucleases	Intestinal glands	Nucleosides	Sugars and nitrogenous bases