Question

Which one is both osmoregulatory as well as a nitrogenous product?
A. $NH_3$
B. Urea
C. Uric acid
D. All of the above

Answer 1

Hint: Metabolic wastes or excrements are substances leftover from metabolic processes such as cellular respiration, which cannot be used by the organism like surplus or toxic. So, these must be excreted. This includes nitrogen compounds, water, sulfates, etc.

Complete answer: The nitrogen compounds like ammonia, urea, uric acid, and creatinine, excess nitrogen eliminated from organisms are called nitrogenous wastes or nitrogen wastes. All of these substances are produced from protein metabolism. Urea is both a nitrogenous product as well as an osmoregulator. It is an excretory product in mammals, Ascaris, earthworms, fishes, etc. Urea is excreted through urine. The urea helps in osmoregulation by participating in the counter-current system, small amounts of urea enter the thin segment of the ascending limb of Henle’s loop which is transported back through the collecting tubule interstitium.
Hence, the correct answer is Option B.
Additional information: -
Nitrogenous waste takes three forms:
1. Ammonia – It is the direct waste produced as a byproduct of protein metabolism. Produced by all animals.
2. Urea – It is formed by the conversion of ammonia in the liver.
3. Uric acid – In reptiles and aves, uric acid is formed by the conversion of ammonia in the liver.

Note: Osmoregulation is the active process in which the osmotic pressure of body fluids of an organism is detected by osmoreceptors, which helps to maintain the homeostasis of water content in the organism's body that is to maintains the fluid balance and the concentration of electrolytes (like salts which represents the body fluid), to keep the body fluids from becoming too diluted or concentrated.