[[Excretion]]
Metabolic reactions occuring within the body produce unwanted substances.
Some are toxic
Excretion if the removal of these waste products.
The two products made in greater amounts than most in the human body are CO2 and Urea.
* CO2 is produced continuously by every cell in the body by aerobic respiration The waste CO2 is transported via blood to the alveoli where it is excreted into the air that we breath out.
*Urea is produced un only one organ in the body: The Liver
Its is produced from excess amino acides and is transported from the liver to the kidnesy, in solution in blood plasma.
The kidneys remove urea from the blood and excrete it dissolved in water as urine.
[[Deamination]]
More Protien is eaten than is needed, the excess cannot be stored. It is wasteful to get rid of the excess however, as amino acids contain useful energy. The nitrogen atoms are removed from the amino acide molecules in the liver. The amino acide molecule is kept, the nitrogen is excreted as Urea.
This process is deamination.
NH3 is removed from the amino acid, leaving C(R)OCOOH and NH3 (keto acid and ammonia)
The keto acid can be converted into a carbohydrate and used in respiration, or could be converted into fat and stored.
Ammonia is highly soluble and toxic. For this reason, it is immediatly converted to the less soluble and less toxic compound Urea
2NH3 + C02 ---> C(NH2)2O + H2O
An adult produces 25-30g a day
Humans also produce other nitrogenous waste compunds, such as creatinine and uric acid.
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