Question

Consider the following statements for deoxy hemerythrin and deoxy-hemocyanin:
A.They are involved in ${O_2}$ transport in biological system
B.They contain two metal ions in their active site
C.Active site metal centres are bridged by amino acid residues
D.They prefer to bind only one ${O_2}$ per active site
E.The correct statements are

Answer 1

Hint: We have to remember that Hemocyanin is utilized for the transport of oxygen in several arthropods such as spiders, centipedes and in mollusks. It is accountable for the bluish-green color of their blood. An oligomeric protein that is accountable for oxygen transport in the phyla of sipunculids, and brachiopods in the marine invertebrate is hemerythrin.

Complete answer:
We need to remember that in deoxy hemerythrin, the two atoms of iron are present in the ferrous oxidation state containing bridging hydroxyl groups. As dioxygen is attached to the active site the atom of hydrogen from the hydroxyl bridge goes over onto the attached ligand strengthening the peroxo nature of the attached molecule of oxygen. In met- derivatives of the protein, in the presence and absence of small molecules attached to the complex, the iron atoms are both present in the ferric oxidation state.
Hemocyanin is the protein that is made up of polymeric subunits that each comprises two copper atoms (rather than iron), with an approximate molecular mass of higher than 1,000,000 amu.
We must know that the deoxy hemocyanin has two $C{u^ + }$ ions per subunit and does not possess any color, but oxyhemocyanin has two $C{u^{2 + }}$ ions and the colour is bright blue. As with hemerythrin, the attaching and liberation of oxygen match to a reaction of two-electrons.
We need to remember that the deoxy hemocyanin and deoxy hemerythrin contains active metal centers and they are bridged by residues of amino acids. In the biological system, both these compounds are involved in the transport of oxygen. They bind with one oxygen atom per active site.
So Options (A), (C) and (D) are correct.

Note:
We must know that even though hemocyanin and hemerythrin helps in the same basic function as hemoglobin, these proteins are not exchangeable. In fact, hemocyanin is so foreign entity to humans that it is one of the main reasons responsible for the mutual allergies to shellfish.