Question

Highest organic constituent of urine?

Answer 1

The excretory waste in animals mainly consists of nitrogen and it excretes out in form of ammonia, urea or uric acid which get produced by protein metabolism. Urine is made up of water, organic and inorganic substances out of which $95\%$ is water and $5\%$ are remaining substances.

Complete Answer:
Urine is a transparent pale yellowish fluid consisting of pigment urochrome. It is slightly acidic with a specific gravity of 1.015. Urine consists of $95\%$ of water and $5\%$ of organic and inorganic substances. The organic compounds consist of a nitrogenous compound like urea, uric acid, creatinine and hippuric acid with some non-nitrogenous compounds like vitamin C, oxalic acid and phenolic substances.
The inorganic compounds in urine are ammonia, minerals salts like chlorides, sulphates and phosphates of sodium, potassium, calcium and magnesium.

Additional Information:
The formation of urea takes place in the liver by a cyclic process known as the urea cycle and ornithine cycle. The urea cycle completes in five steps by the presence of five distinct enzymes out of which the two enzymes are present in mitochondria and three in the cytosol. In the first step, the enzyme carbamoyl phosphate synthase converts ammonia and carbon dioxide into carbamoyl phosphate. In the second step, ornithine transcarbamylase converts carbamoyl phosphate into citrulline. In the third step citrulline forms argininosuccinate by enzyme argininosuccinate synthase. The argininosuccinate in the fourth step cleaves into arginine and fumarates by and in the last step the arginine splits and gets converted into ornithine and urea by enzyme arginase.

Note:
The pigment of urine like urochrome is derived by the breakdown of haemoglobin formed from the worn-out RBCs. The colour of urine gets changed due to disease, food composition and drugs.
The principal mineral salt present in urine is sodium chloride and due to the bacterial degradation of urea to ammonia the urine smells like ammonia.