Digestion 3.1.1/3.1.2

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  • Digestion
    • Digestion is progressive hydrolysis
      • Starch to maltose to glucose by adding more water each time
        • Starch is a polymer and a polysaccharide
        • Maltose is a disaccharide
        • Glucose is a monomer and a monosaccharide
    • Mammals use enzymes as biological catalysts to speed up digestion as the enzymes breaks the food into more soluble, smaller pieces
    • Gut functions
      • Mechanical digestion
        • Breaking up chunks of food- it occurs in the mouth and stomach
      • Chemical digestion
        • Breaks bonds
      • Absorption
      • Excretion/ egestion
        • Waste removal
    • Gut structure
      • Mouth to oesophagus to stomach to duodenum to ileum to colon to rectum to anus
      • Glands outside the gut wall
        • Salivary glands, liver, gall bladder, pancreas
      • 3 main layers
        • Muscle as the outer layer for churning and perastalsis
        • Submucosa is the middle layer for transport
        • Mucoasa as the inside layer has various levels of folding
    • Chemical digestion is when a substrate is hydrolysed by an enzyme
      • Starch to maltose by adding water and amylase then the products are absorbed
    • Process of digestion
      • 1. Mouth - physical digestion, salivary amylase is made to aid carbohydrate digestion, chemical digestion begins, extracellular digestion occurs, saliva lubricates food for ease movement
      • 2. Oesophagus- mucus lubricates to food to aid peristalsis down the osephagus
      • 3. Stomach- food can be stored, protein digestion begins, churning of the food occurs
      • 4. Duodenum- most of the digestion occurs here, enzyme production occurs
      • 5. Ileum - digestion is completed, absorption occurs
      • 6. Colon - water and ions are remove, faeces are formed
      • 7. Rectum -  faeces are stored
    • Carbohydrate digestion begins in the mouth and finishes in the duodenum and occurs via the use of pancreatic amylase which hydrolyses the sugar bonds creating pairs of sugars - disaccharides


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