Question

Respiratory pigment of arthropods is
A. Haemoglobin
B. Cytochrome
C. Haemocyanin
D. None of the above

Answer 1

Hint: Respiratory pigments are the pigments which increase the oxygen carrying capacity of the blood. It also functions in exchange of gases. In the vertebrates the respiratory pigment is found in the erythrocytes in the blood.

Complete Answer:
To solve this question, we must know about different types of respiratory pigments and where they are present.
Respiratory pigments play an important role in transport of oxygen to different parts of the body. Few examples of respiratory pigments are haemoglobin haemocyanin, chlorocruorin etc.
- Haemoglobin: It is a red colour pigment present in the blood of many animals including human beings. It is an iron containing pigment which transports oxygen and carbon dioxide to the tissues and organs.
- Cytochrome: Cytochrome is a heme containing protein which is present in mitochondria. It consists of central Fe molecules. Its main function is transfer of energy within the cell.
- Haemocyanin: It is a copper containing pigment which is present in the invertebrates like arthropods and molluscs. Unlike haemoglobin, it does not bind with the blood cells rather they are freely found in the haemolymph.

Thus the correct answer is (C). Respiratory pigment of arthropods is haemocyanin.

Additional Information: Chlorocruorin is present as respiratory pigment in annelids like earthworms.

Note: Haemocyanin is the respiratory pigment found in molluscs and arthropods. It is colourless in the deoxygenated form and turns blue when oxygenated due to the presence of copper in the pigment. It has 2 copper atoms at the centre which binds with the single oxygen molecule.