Question

Nitrogenous wastes are formed from the breakdown of
A. $NH_3$
B. Fat
C Amino acids
D. water

Answer 1

Nitrogenous wastes or nitrogen wastes are nitrogen compounds through which the excess of the nitrogen is eliminated from the body of the organism. The nitrogen wastes include ammonia, urea, uric acid, and creatinine. These substances are generated from protein metabolism.

Complete answer:
The major two nitrogenous wastes are: urea and uric acid. Urea is produced from the metabolism of amino acids and uric acid is produced from the metabolism of nucleotides. The urea is the primary nitrogenous waste formed by the breakdown of amino acids in the body. Mammals are the main producers of urea as they secrete urea as the major nitrogenous waste product in the body. These animals are called ureotelic animals. Urea plays a significant role in the metabolism of nitrogen-containing waste compounds by animals. It is the primary nitrogen-containing compound in the urine of the mammals including humans. The urea cycle contains the multi-step conversion which is carried out by five different enzymes. These enzymes convert the amino acid L- ornithine into different intermediates and finally is converted into nitrogenous waste i.e. urea and uric acid.
So, the correct answer is option (C).

Additional Information:
Ureotelic animals are animals that produce urea as the primary nitrogenous waste material. Urea is less toxic than ammonia and it requires lesser water. Ureotelic animals include bony fishes, amphibians, cartilaginous fishes and mammals including humans.

Note: The organisms which excrete uric acid as the waste material are known as uricotelic organisms. Uric acid is the least toxic and is least soluble in water as compared to other nitrogenous wastes such as Ammonia and Urea. Uricotelic animals include birds, snakes and lizards.