Question

Pigment hemocyanin occurs in
a. Echinodermata
b. Mollusca
c. Chordata
d. Annelida

Answer 1

Hint: Hemocyanin is the protein, which is helpful for the transport of oxygen throughout the body in invertebrate animals, unlike the hemoglobin pigment found in the red blood cells, hemocyanin do not bound to blood cells, and they directly suspend in the hemolymph.

Complete answer:
- Species distribution: Hemocyanin pigment is essentially found only in the species of Mollusca and arthropods.
- Whereas the earliest discovery of the hemocyanin is observed in the snail and horseshoe crabs.

> Structure: Hemoglobin contains iron atoms, whereas hemocyanin contains the two copper atoms, which is directly coordinated by the 6 histidine residues.

> Function: Each metalloprotein of the hemocyanin contains two copper atoms, which bind the single oxygen molecule, and the attachment is reversible.
- Hemocyanin is the next pigment to hemoglobin to transport the oxygen.
- Spectroscopy of oxyhemocyanin shows that it is symmetrical and it does not have any unpaired electrons.
- Oxygenation of hemocyanin causes the color changes, which are deoxygenated form is colorless, while the oxygenated one is blue in color.
- In arthropods, hemocyanin is composed of Phenoloxidase, they are copper-containing tyrosine. These proteins are involved in some processes, such as sclerotization of arthropod cuticles in wound healing, and in immune defense.
- So hemocyanin is the pigment with metalloproteins found in some invertebrates.

Hence, the correct answer is option (B).

Note: The evolutionary changes in the phylogeny of the hemocyanin superfamily are generally very closely related to the emergence of different types of proteins, in different varieties of species. So In order to understand those proteins, extensive study of arthropods hemocyanin is important.