The digestive system breaks down food and absorbs it into the blood stream.

Large, insoluble molecules are broken down by enzymes into small, soluble molecules that can pass through the wall of the small intestine into the blood by diffusion.

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  • Digestion
    • Food Tests
      • Starch
        • Add iodine
        • Colour change from brown to blue/black
      • Glucose
        • Add Benedict's solution and heat in a water bath
        • Colour change from blue to green then orange and finally brick red
      • Protien
        • Add Biuret solution
        • Colour change from pale blue to purple
      • Bomb Calorimeter
    • Bile
      • Made in the liver
      • Stored in the gall bladder
      • Transported to the small intestine through the bile duct
      • It emulsifies fat to aid digestion by lipase
      • Bile is alkaline. it neutralises the contents of the stomach
        • This provides optimal conditions for enzyme action
    • Peristalsis
      • Muscles contract and relax to push food through the digestive system
    • Enzymes
      • Amalayze
        • Digests starch into glucose
        • Found in the Salivary glands, Pancreas and small intestine
      • Protease
        • Digests protein into amino acids
        • Found in the stomach, pancreas and small intestine
          • Untitled
      • Lipase
        • Digests fats into fatty acids and glycerol
        • Found in the pancreas and small intestine
      • Enzyme Theory
        • All enzymes are proteins
        • Enzymes are biological catalysts (they speed up reactions)
        • Enzymes can be used millions of times
        • The substance that the enzyme digests is called substrate
        • Each enzyme can only work on one substrate. It is specific
        • Enzymes can be effected by temperature and pH
          • The optimum temperature for the reaction is 37 degrees
          • At higher temperatures the enzyme denatures and the substrate can no longer fit the active site
        • Lock and Key Theory
    • Diagram
    • Absorbtion
      • Absorbtion of food occurs in the small intestine
        • the small intestine allows soluble molecules to pass through into the blood stream
        • Visking tubing can be used to mimic this
      • Water is reabsorbed in the large intestine
      • Villi
        • Digested carbohydrates and proteins are absorbed into blood capillaries
        • Digested fats are absorbed into lacteals
    • Components of diet
      • Carbohydrate
        • Required for energy
      • Protien
        • Required for growth and repair
      • Fat
        • Required for insulation and energy store
        • Saturated fat clogs arteries and can lead to heart disease
      • Vitamins
      • Minerals
      • Fiber
      • Water
      • Too much sugar leads to tooth decay and type II diabetes
      • Too much salt leads to high blood pressure or a stroke


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