Chemical transformation of Food

• Digestion includes :


  2 types of transformation that take place at the same time:

  1. Mechanical transformation: Mechanical digestion
  2. Chemical transformation: chemical digestion
• Mechanical transformation

  change in the aspect (size-shape) of food

  ---> like chewing, mastication, etc...
• Chemical transformation


  change in the identity of food

  --> Like: starch -> maltose -> glucose.
• Organs of digestive tube and the mechanical/ chemical digestion's role

  • Mouth
  • Mechanical digestion: Mastication (food is cut, torn, and grinded)
  • Chemical digestion: Mixing of food with saliva
  • Pharynx
  • Mechanical digestion: —
  • Chemical digestion: —
  • Esophagus
  • Mechanical digestion: —
  • Chemical digestion: —
  • Stomach
  • Mechanical digestion: Churning
  • Chemical digestion: Mixing of food with gastric juice
  • Small intestine
  • Mechanical digestion: Churning and bile action
  • Chemical digestion: Mixing of food with intestinal and pancreatic juices
  • Large intestine
  • Mechanical digestion: —
  • Chemical digestion: —
• Digestion : 


  It is the set of chemical and mechanical transformation that allows the gradual breaking down of complex food into simpler food called nutrients
• Digestive system 


  --> Digestive tube/tract: where food passes

  • It is the set of organs where the food passes.
  • Mouth -> pharynx -> esophagus -> stomach -> small intestine -> large intestine -> anus

  --> Digestive glands: where food doesn't pass

  • It is an organ which secrets a digestive juices ( that contains enzymes) responsible for the digestion of food.
• Examples of digestive glands

  • Salivary glands (in the mouth): secrets saliva
  • Gastric glands (in the stomach): secrets gastric juice
  • Intestinal glands (in the small intestine): secrets intestinal juice
  • Pancreas: which secrets pancreatic juice
  • Liver: it is an accessory gland that secrets a juice called bile (doesn't contain enzymes).
• Role of bile


  responsible for the emulsification (separation) of lipids=fats.