Question

Why is there a need for the respiratory pigment in multicellular organisms?

Answer 1

Hint: They help to increase the supply of oxygen and transportation in the organisms.

Complete answer:
Respiratory pigments are the molecules which consist of protein with the pigment prosthetic group. They help in the process of transport of oxygen and electrons in plants. In humans, the respiratory pigment is a molecule that increases the oxygen affinity in the blood. A common example is a hemoglobin which has the high capacity to carry oxygen in blood in vertebrates and humans.
Hemoglobin is attached to the red blood cells of the blood carrying oxygen to various body parts. If the blood is oxygenated then hemoglobin will be bright red but if the blood is deoxygenated the hemoglobin will be purplish. Other respiratory pigments are hemocyanin, hemerythrin, and chlorocruorin present in the blood.
Hemocyanin is blue colored pigment when the blood is oxygenated but if the blood is deoxygenated then it will be colorless. Similarly, chlorocruorin turns from green to red when it is oxygenated. The hemerythrin when oxygenated turns violet to pink but if it is deoxygenated it turns colorless. These respiratory pigments store oxygen and act as a buffer to increase the capacity of carrying the carbon dioxide.

Note: Haemoglobin is an iron-containing metalloprotein which carries oxygen in the red blood cells from the lungs to various parts of the body. The properties of hemoglobin were discovered in 1840 by Hunefeld. The molecular structure of hemoglobin was determined in 1959 by Max Perutz. The word hemoglobin is derived from the words heme and globin.