Excretion Revision Notes
Importance Excretion
-it is the removal of metabolic waste from the body (unwanted products of cell metabolism)
-CO2, bile pigments and nitrogen containing compounds (urea) all need to be excreted
-prevents them building up and becoming toxic or inhibiting enzyme action
Excretory Organs
Lungs
-CO2 is passed from respiring tissues into the blood stream where in is transported (form of HCO 3- ions) into the lungs
-CO2 diffuses into the alveoli and is excreted (exhaled)
Liver
-some substances produced will be passed into the bile for excretion
-converts excess amino acids to urea (deamination)
Kidney
-urea is removed from the blood stream and concentrated into urine for excretion
Skin
-sweat contains salts, urea, uric acid and ammonia
-uric acid and ammonia are excretory products
-loss of salts and urea will be important for homeostasis
Carbon Dioxide
-most transported by hydrogen carbonate ions
1) CO2 + H2O H2CO3
2) H2CO3 H+ + HCO3-
-occurs in red blood cells – enzyme carbonic anhydrase catalyses reaction
-H+ ions changes the tertiary structure of the red blood cell
-reduces red blood cell’s affinity to oxygen, affecting transport of oxygen
-H+ combines with haemoglobin to form haemoglobinic acid
-CO2 combines with haemoglobin to for carbaminohaemoglobin
-Both haemoglobinic acid carbaminohaemoglobin does not bind with O2 reducing the capacity further
-Excess H+ ions reduce pH of plasma altering proteins tertiary structure
-These proteins transport a wide range of substances
-The proteins act as a buffer to maintain pH
-Medulla oblongata detects excess H+ increasing respiration to remove CO2
Nitrogenous Compounds
-body cannot store amino acids but they contain a lot of energy (cannot waste)
-toxic amino group removed by deamination in the liver
-ammonia formed is then converted to urea which is transported to the kidneys for excretion
Deamination: amino acid + oxygen → keto acid + ammonia
Formation of Urea: ammonia + carbon dioxide → urea + water
2NH3 + CO2 → (NH2)2CO + H2O
Importance Excretion
-it is the removal of metabolic waste from the body (unwanted products of cell metabolism)
-CO2, bile pigments and nitrogen containing compounds (urea) all need to be excreted
-prevents them building up and becoming toxic or inhibiting enzyme action
Excretory Organs
Lungs
-CO2 is passed from respiring tissues into the blood stream where in is transported (form of HCO 3- ions) into the lungs
-CO2 diffuses into the alveoli and is excreted (exhaled)
Liver
-some substances produced will be passed into the bile for excretion
-converts excess amino acids to urea (deamination)
Kidney
-urea is removed from the blood stream and concentrated into urine for excretion
Skin
-sweat contains salts, urea, uric acid and ammonia
-uric acid and ammonia are excretory products
-loss of salts and urea will be important for homeostasis
Carbon Dioxide
-most transported by hydrogen carbonate ions
1) CO2 + H2O H2CO3
2) H2CO3 H+ + HCO3-
-occurs in red blood cells – enzyme carbonic anhydrase catalyses reaction
-H+ ions changes the tertiary structure of the red blood cell
-reduces red blood cell’s affinity to oxygen, affecting transport of oxygen
-H+ combines with haemoglobin to form haemoglobinic acid
-CO2 combines with haemoglobin to for carbaminohaemoglobin
-Both haemoglobinic acid carbaminohaemoglobin does not bind with O2 reducing the capacity further
-Excess H+ ions reduce pH of plasma altering proteins tertiary structure
-These proteins transport a wide range of substances
-The proteins act as a buffer to maintain pH
-Medulla oblongata detects excess H+ increasing respiration to remove CO2
Nitrogenous Compounds
-body cannot store amino acids but they contain a lot of energy (cannot waste)
-toxic amino group removed by deamination in the liver
-ammonia formed is then converted to urea which is transported to the kidneys for excretion
Deamination: amino acid + oxygen → keto acid + ammonia
Formation of Urea: ammonia + carbon dioxide → urea + water
2NH3 + CO2 → (NH2)2CO + H2O
