Excretion Unit 1 Mod. 2 A2 Biology

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  • Excretion
    • 2 Main Substances Excreted
      • Carbon Dioxide (CO2)
        • Produced By:
          • Every living body cell (due to respiration)
        • Where excreted?
          • Breathing Out
            • Process?
              • CO2 - waste product of aerobic respiration from every living body cell
                • Enters bloodstream (mostly in form of    hydrogencarbonate ions)
                  • Transported to Lungs
                    • CO2 diffuses into Alveoli
                      • Excreted as we breathe out
      • Urea (Nitrogen Containing Compounds)
        • Produced By:
          • Liver (from excess amino acids)
        • Where excreted?
          • Urine via Uretha
            • Process?
              • Excess amino acids
                • Broken down in Liver
                  • Passed into bloodstream
                    • Transported to Kidneys
                      • Dissolved in Blood Plasma
                      • In Kidneys, Urea removed from blood to become part of urine
                        • Stored in Bladder
                          • Excreted via Uretha
                  • Called -deamination
        • Formed By
          • Ammonia + CO2
            • Makes
              • Urea + Water
    • Definition
      • The removal of metabolic waste from the body
    • Reason for excretion
      • CO2
        • Excess CO2 toxic
          • Has 3 main effects
            • AS - level "chloride shift"
              • Most CO2 in blood as Hydrogencarbonate ions
                • Forming these ions also forms Hydrogen ions
                  • H+ ions combine with haemoglobin
                    • Compete with oxygen for space on haemoglobin
                      • Therefore can reduce Oxygen transport
            • CO2 combines directly with haemoglobin to form carbaminohaemoglobin
              • This molecule has a lower Affinity for oxygen than normal haemoglobin
            • Excess  CO2 can cause respiratory acidosis
              • CO2 dissolves in blood plasma
                • CO2 + H2O
                  • H2CO3
                    • Dissociates to
                      • H+ and HCO3-
                        • H+ ions released therefore lowering pH
      • Nitrogenous Compounds
        • Body can't store proteins/ amino acids
          • Transported to Liver
            • Poentially toxic amino acid group removed (deamination)
              • Amino group initially forms highly toxic and highly soluble compound Ammonia
                • In Liver, converted into less toxic and less soluble Urea
                  • Urea transported (in blood plasma) to Kidneys for excretion
                    • Remaining Keto acid
                      • Used directly in respiration
                      • converted to carbohydrate or stored as fat
              • Deamination
                • Amino Acid + Oxygen
                  • Makes
                    • Keto Acid + Ammonia
    • Remember!
      • Do not confuse Egestion or Elimination with Excretion!

Comments

Stewie Griffin

Nice one, buddy!

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