Tag: zoology

The characteristic shared by urea, uric acid and ammonia are they are nitrogenous wastes. In comparison to Ammonia and Urea, uric acid is the least toxic and the least soluble in water. It can be stored in cells and body tissues without any toxic effects and hence needs less water for excretion when compared to Ammonia and urea.

For terrestrial vertebrates, nitrogenous wastes are removed from body fluids by the action of the kidneys, the same organ involved in maintaining water balance. Ammonia the direct waste produced as a byproduct of protein metabolism.  Produced by all animals.  Because of its toxicity, many animals convert ammonia into a less toxic form.  Any conversion of ammonia into other forms comes at a price, for animals must expend cellular energy (ATP) to convert ammonia to either form of nitrogenous waste listed below.

Chemicals that the body makes when there is not enough insulin in the blood and it must break down fat instead of the sugar glucose for energy. The ketone bodies -- acetone,  acetoacetate, and beta-hydroxybutyrate -- are toxic acidic chemicals. They build up in the blood and then spill over into the urine. The body can also rid itself of acetone through the lungs. This gives the breath a fruity odor.

Urea synthesis is a five-step cyclic process, with five distinctive enzymes. One turn of the cycle consumes 2 molecules of ammonia and  1 molecule of carbon dioxide and creates 1 molecule of urea ((NH2)2CO. Hence  16  molecules of ammonia are required to form 8 molecules of urea.

Ammonia is more water soluble and more toxic than Urea or uric acid. Ammonia is extremely toxic and its accumulation in the body can be lethal. So the liver converts toxic ammonia into less toxic urea through the urea cycle.

Ketone bodies are byproducts in the metabolism of fat. During starvation or fasting conditions the liver synthesizes glucose through a process called gluconeogenesis. Gluconeogenesis is a metabolic pathway that results in the generation of glucose from fat. During gluconeogenesis, the ketone bodies are formed as byproducts where the product is glucose. The Kerone bodies consist of acetoacetic acid, acetone and beta-hydroxybutyric acid.

• Birds, reptiles, and fishes produce uric acid waste and they are called Uricothelic organisms.
  
• They tend to excrete uric acid as its waste which is in the form of a white paste or powder.
• Producing uric acid over urea is advantageous because it is less toxic and reduces water loss and the subsequent need for water.  in these organisms.
• The correct answer is OPTION A.

When muscles work continuously enough, oxygen is not reached to muscles to burn glucose aerobically in such conditions glucose is converted into lactic acid i.e anaerobic glycolysis. The lactic acid produced in muscles is moved to the liver and converted to glucose. In ureotelic organisms, lactic acid is converted into Glucose through the Cori cycle. This metabolic cycle was discovered by Carl Ferdinand Cori and  Gerty Cori, hence named Cori cycle.