Question

Explain the composition of urine.

Answer 1

Hint: Urine is an excretory product of humans and many other animals. It mainly constitutes nitrogenous waste from the body of an organism. The glomerulus is the first place where the making of urine starts.

Complete answer:
Urine is the byproduct of various metabolic processes that takes place in the vertebrate. It is formed in the kidneys of animals and generally stored in the urinary bladder. The process of excretion of urine through the urethra is called urination.
-Urine is composed mainly of water along with some organic and inorganic matters. The water constitutes about $95\mathrm{\%}$ and the remaining are solid.
-The organic solids consist of proteins, hormones, pigments, metabolites, etc. and the inorganic components consist of ions of sodium, potassium, chlorine, nitrogen, and other trace elements.
-During diseases and other conditions, the urine may consist of macromolecules of proteins, hemoglobin, carbohydrates, huge amounts of pigments, etc. Hence urine samples are collected to detect any disease of the body to study its color and composition that can lead to the cause of the disease.
-Humans are ureotelic in nature as the waste product excreted is in the form of urea while in the case of reptiles and birds excretory waste product is uric acid, hence they are called uricotelic organisms. In aquatic organisms, waste products release ammonia so they are called ammonotelic organisms.

Note:
Urine is generally pale yellow in color due to the presence of bile pigments that are formed in the hepatocytes of the liver due to the breakdown of hemoglobin. But during cases of the disease, the color of urine may change because of the presence of other components. For example, if a person has jaundice the urine is dark yellow colored due to excess bile, or if hemoglobin is excreted through urine it may be red-colored. Black or dark-colored urine may suggest that the person suffers from melanoma.