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  • 5.2.1 - Excretion
    • Excretory Organs
      • Lungs - CO2 diffuses into alveoli to be excreted when we breathe out.
      • Liver - many metabolic roles, substances passed into the bile for excretion with faces i.e. bilirubin
        • - Also converts excess amino acids to urea- deamination
      • Kidneys - urea passed to kidneys through bloodstream in plasma - removed from blood to become part of urine.
        • Urine stored in bladder before being excreted from body via urethra.
      • Skin - sweat contains salts, urea, uric acid, ammonia, water - all excretory products.
        • Skin involved in excretion but not primary function of the skin.
    • Importance of excretion
      • Danger of build up of products of metabolism
      • CO2 and ammonia = toxic
        • Interfere with cell processes - alter pH, normal metabolism is prevented
      • Products may act as inhibitors - reduce activity of essential enzymes.
      • CO2
        • Most CO2 transported as hydrogen carbonate ions.


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