BY2 Nutrition (2)

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  • BY2 - Nutrition (2)
    • Mammalian Gut; Digestive System & Alimentary Canal
      • Mouth
        • Mechanical digestion by the teeth.
          • Increases surface area for enzyme action.
        • Alkaline
      • Stomach
        • Acidic
          • Optimum pH for enzymes and kills bacteria.
        • Mechanical digestion
          • Chemical digestion
        • Glands release gastric juice
        • Mucus is released
          • Lubrication and prevents auto digestion (enzymes digest stomach walls
      • Small Intestine - Duodenum
        • Secretes an alkaline liquid.
          • From the Brunner's gland.
        • Pancreas releases pancreatic juice.
          • Enters duodenum via pancreatic duct.
          • Contains amylase, endopeptidase and lipase.
            • Exopeptidases hydrolise peptide bonds on terminal amino acids.
            • Polypeptides ---> Peptides
        • Bile enters via the bile ducts.
          • Contains bile salts.
            • Neutralise stomach acids.
            • Emulsify lipids
        • Goblet cells release mucus.
      • Small Intestine - Ilium
        • Methods of Transport
          • Glucose and amino acids are absorbed across the epithelium of the villi via diffusion and active transport (if the diffusion rate is too slow).
            • They pass into the capillary of the villus and are then transported to the hepatic portal vein to the liver.
          • Fatty acids and glycerol are absorbed into the lacteal via diffusion.
            • They are transported to the lymphatic system which opens up into the blood stream at the thoracic duct.
        • Absorption Features
          • Large Capillary Network
            • Absorbs glucose and amino acids
            • Maintains concentration gradient.
          • Lacteal or Lymph Vessel
            • Absorbs fatty acids and glycerol.
          • Thin Epithelium
            • Short diffusion pathway.
          • Ilium is long.
            • Increases surface area to increase rate of diffusion.
              • Villi
          • Villi
          • Lots of Mitachondria.
            • Provides ATP for active transport.
      • Large Intestine
        • Colon, appendix and rectum.
        • Function is to reabsorb water and minerals back into the blood stream.
        • Vitamins are secreted by bacteria (E-coli) e.g. vitamin K.
          • When the food reaches the rectum it is in a semi solid condition.
            • e.g Faeces
              • Consist of undigested food (cellulose, bacteria and dead cells).
      • Fate of Digested Products
        • Glucose releases energy into respiration.
        • Amino acids are used in protein synthesis.
          • Or they are deaminated (amine group is removed) and converted into urea.
        • Lipids used for membranes and hormones.
          • Or stored as fat under the skin.
    • Dentition
      • Types of Teeth
        • Molars
          • For chewing and grinding.
        • Incisors
          • For slicing and cutting.
        • Canines
          • For ripping and tearing.
      • Herbivores
        • Jaw moves in horizontal plane (side-to-side).
        • No canines.
        • No carnassial teeth.
          • Open roots for continuous growth.
        • Cheek teeth are flattened with enamel ridges.
          • Molars/Pre-Molars are in a ridged W-M arrangement.
        • Diastema - separates front teeth from the pre-molars and helps to chew food.
        • Cellulose is part of diet.
      • Carnivores
        • Canines present.
        • Jaw movement is vertical (mouth opens wider to grip onto prey).
          • Well developed jaw muscles powerful enough to crush bones.
        • Carnassial teeth.
          • Pointed cheek teeth.
          • No W-M arrangement.
        • Incisors in upper and lower jaw.
        • No horny pad.
          • No diastema.
        • Teeth do not grow continuously.
        • No cellulose in diet.
    • Herbivore Gut
      • Long
        • More difficult to digest plant material.
        • Larger caecum.
          • Contains bacteriato help digest plant material.
      • Carnivore Blood
        • Short
          • Shows how easily protein is digested.
        • Shorter caecum.
          • Don't need to digest plant material.
        • Caecum contains bacteria to digest cellulose.
      • Rabbits eat their droppings in a process called refection for more time to absorb nutrients.
    • Ruminants
      • Specialised stomachs have mutualistic bacteria - both organisms benefit from the relationship.
      • e.g. Cow
        • 1. Grass enters rumen which contains cellulose digesting bacteria - celluloses moves into the second chamber.
          • 2. Cud is regurgitated for further chewing and then swallowed to move into the next chamber, where water is reabsorbed.
            • 3. Cud enters the final chamber - the 'true stomach' where protein is digested.
              • Fermentation takes place which produces CO2 and methane gases (CH4).
              • When the bacteria die they provide a source of protein for the cow.
      • Cellulose is digested into glucose in the rumen.
  • Salivary glands produce saliva
    • Lubricates food.
    • Mouth
      • Mechanical digestion by the teeth.
        • Increases surface area for enzyme action.
      • Alkaline
  • Microvilli
    • Increases surface area to increase the rate of diffusion.
    • Absorption Features
      • Large Capillary Network
        • Absorbs glucose and amino acids
        • Maintains concentration gradient.
      • Lacteal or Lymph Vessel
        • Absorbs fatty acids and glycerol.
      • Thin Epithelium
        • Short diffusion pathway.
      • Ilium is long.
        • Increases surface area to increase rate of diffusion.
        • Lots of Mitachondria.
          • Provides ATP for active transport.

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