Tips and Tricks

• The process of elimination of metabolic wastes from the body is called excretion.’

• There are three types of nitrogenous wastes. They are ammonia, urea and uric acid.

Follow up:

AMMONIA

• It is an important nitrogenous waste produced during protein metabolism.

• It is highly toxic but highly soluble in water.

• Ex. Bony fish, Tadpole larva, coelenterates, echinodermates.

UREA

• It is a nitrogenous waste and a product of ammonia.

• Urea is less toxic and less soluble.

• Terrestrial animals eliminate urea as a waste product. Ex.- Amphibians, Mammals.

UREA SYNTHESIS

• Urea synthesis occurs in liver, the process of conversion of toxic ammonia into less toxic urea is called urea cycle (or) ornithene cycle or Krebs’s cycle.

• Ammonia is produced by deamination of amino acids combines with  by using two molecules of

• ATP to form carbamoyl phosphate.

• Carbomoyl group is transferred to ornithene to form citrulline and

• Citrulline combines with another amino acid (asparatate) by using ATP to form arginino succinate and it splits into arginine and fumarate.

• Arginine regenerated again and again in the cycle and urea is taken to kidney where it is converted into urine.

URIC ACID

• It is a nitrogenous waste and a product of purines and pyramidines.

• It is least toxic and least soluble in water and formation occurs in it is the only nitrogenous waste eliminated in semi solid form along with fecus.

• Ex. Snails, insects, reptiles and birds.

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