Question

The characteristic(s) common to urea, uric acid and ammonia is/are:
i. They are nitrogenous wastes.
ii. They all need a very large amount of water for excretion.
iii. They are all equally toxic.
iv. They are produced in the kidneys.
(a) i, ii and iv
(b) i only
(c) i and iii
(d) i and iv

Answer 1

Hint: Urea, uric acid, ammonia- all of these are derivatives of nitrogen.

Complete answer:In vertebrates, three types of excretory waste are produced: ammonia, uric acid and urea. All of them are derivatives of nitrogen and they are produced as by-products during metabolism of various proteins and amino acids in our body. Not all of them are equally toxic.
Ammonia is excreted mainly by the aquatic animals. It is highly toxic and so excreted out without any delay. Ammonia also needs more water to get dissolved and excreted. Uric acid is excreted by birds. It needs the least amount of water to get excreted out. So, the correct option is B. i only.

Additional information:In Mammals, the excretory product is urea which is moderately toxic and requires a certain amount of water for excretion. Hence, all of these are not equally toxic and also the three compounds do not require equal amounts of water for excretion. Ammonia is produced in the liver. Urea is also produced in the liver by urea cycle. Uric acid is produced in the liver and some amount in the kidney.
So, the only common thing in all the three compounds is that- these are nitrogenous wastes.

So, the correct option is B. i only.

Note: Ammonia is also produced in the human body but it is immediately converted to urea to reduce the toxicity and excreted as urea.