Nutrition in Humans

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  • Created by: MaisyAbel
  • Created on: 25-10-15 19:17
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  • Nutrition in Humans
    • a balanced diet should include appropriate proportions of:
      • carbohydrates
      • lipids
      • Proteins
      • vitamins and minerals
      • fibre
      • water
    • Energy requirements vary with: ACTIVITY LEVELS, AGE and PREGNANCY
    • The 5 processes of the alimentary canal that transform food
      • INGESTION~ taking food into the body through the mouth
      • DIGESTION~ the mechanical and chemical breakdown of food. Large insoluble molecules are converted to small soluble molecules which can be absorbed into the blood
      • ABSORPTION~ the movement of the soluble products of digestion from the ileum into the blood
      • ASSIMILATION~ the processes by which cells use the soluble products of digestion to build new material
      • EGESTION~ the removal of faeces, the waste products of digestion. These materials have passed through the gut without entering cells
    • Peristalsis
      • there are MUSCLES in the walls of all organs of the alimentary canal
        • these muscles push food along the: oesophagus, small and large intestine
          • there are 2 layers of muscles in the walls of these organs: CIRCULAR MUSCLES and LONGITUDINAL MUSCLES
            • When ONE muscle CONTRACTS the OTHER RELAXES
              • (Waves of muscular contractions push the food along, so the movement of the food is not dependent on gravity and you can eat standing on your head
    • Digestive enzymes
      • PROTEASE ~ Breaks down proteins to amino acids. Produced by the stomach wall
      • LIPASE ~ Breaks down fats to 3 fatty acids and 1 glycerol. Produced by the pancreas
      • AMYLASE ~ Breaks down starch to single sugars (glucose) and disaccharides (maltose). Produced by the salivary glands
      • MALTASE, SUCRASE, & LACTASE ~ Breaks down the sugars: maltose, sucrose and lactose (respectively). All produced by the small intestine
    • Bile
      • Produced by the liver
      • Stored in the gall bladder
      • Neutralises stomach acid
      • Passes along the the bile duct into the duodenum
        • Breaks down large fat droplets into smaller ones)
          • The emulsification means a larger surface area for the lipase to work on
    • Villi
      • After digestion, food enters the blood to be transported around the body
        • This occurs in the main part of the small intestine, the ILEUM
          • The lining of the ileum is covered in millions of small projections called VILLI
            • Adaptations of the ileum: long (6-7 metres), covered with villi, villi are covered in microvilli
            • Adaptations of villi: thin, permeable walls (1 cell thick), contain a network of blood capillaries (which maintain the concentration gradient for quick diffusion of the blood, contain lymph vessels (lacteals) - tubes in the middle of each villi - that absorb the products of fat digestion
    • Experiment (energy content in a food sample)
      • Hold a piece of food under a tube of water, burn the food. When it is fully burned compare the heat of the  temperature before and after. The change in heat is the energy in degrees, convert if needed.


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