Physical and Chemical Digestion

Physical Digestion

• Breaking large pieces into smaller soluble pieces
  - Increase surface area for enzymes to act on
• teeth, stomach

Teeth

Incisors

chisel shaped, In the front middle
Function: bite off pieces of food

Canines

similar to incisors for human, more pointed for carnivores
Function: killing preys (carnivores), bite (human)

Premolars and Molars

wide surfaces, broad, towards the back of the mouth
Function: grinding food to increase its surface area
Premolar has 1 root, Molar has 2 roots

Structure

Enamel: strong material, covers the surface

• Hardest substance made by animals
• Can be dissolved by acids and can feed bacteria if dirty
• Tooth decay: bacteria form plaque; breaking down of sugar releases acid.
  Dentine: living tissue
  Pulp: contains nerves and blood vessels
  Cement: holds tooth in the gum

Bile

Neutralize acidic mixture
Emulsifies fat into tiny droplets of liquid

Chemical Digestion

Starch

1. amylase: (starch into maltose)
   • by salivary glands, pancreas
   • acts in mouth, duodenum
2. maltase (maltose into glucose)
   • By epithelial cells of duodenum
   • acts in duodenum

Starch -> glucose

Protein

1. pepsin (optimum pH 2)
   • by stomach
2. trypsin (optimum pH 7-8)
   • by pancreas
   • acts in duodenum

Protein -> amino acids

Lipid

1. lipase
   • by pancreatic juice
   • acts in duodenum

Lipid -> fatty acid, glycerol