Question

The respiratory pigment with least oxygen carrying capacity is
a. Haemoglobin
b. Chlorocruorin
c. haemoerythrin
d. Haemocyanin

Answer 1

Hint: The different iron-containing pigments are Haemoglobin, Chlorocruorin, Hemoerythrin, and Haemocyanin. They help in the process of respiration. The ratio of iron to oxygen determines the oxygen-carrying capacity.

Complete answer:
> Option A:
Haemoglobin is a red-coloured respiratory pigment found in the vertebrates. It carries oxygen and is found in red blood cells. ‘Heme’ is the iron-containing part and ‘globin’ is the chain of the protein. In haemoglobin, four iron atoms that bind with four oxygen atoms. Thus, the ratio is 1:1 in haemoglobin.

> Option B:
Chlorocruorin is a respiratory protein and is chemically similar to haemoglobin. It is found in some of the marine annelid worms. It is red-green colour and is a respiratory pigment. It carries oxygen in the stream.

> Option C:
Haemoerythrin is responsible for the oxygen flow in many marine animals. It is also responsible for oxygen transfer and storage in the body. It differs from haemoglobin in the type of oxygen binding. The iron to oxygen ratio found in haemoerythrin is 2:1. This means that oxygen-binding in each chain contains two iron atoms. It is found in many marine worms.

> Option D:
Haemocyanin transports oxygen in the bodies of some invertebrates. The active center in haemocyanin has two copper atoms that reversibly bind with a single oxygen molecule. The hemocyanins are carried by hemolymph and are not bound with blood cells.

Hence, the correct answer is option (C).

Note: Haemoerythrin becomes colourless when deoxygenated. It is violet in colour in oxygenated form. It is found in many marine worms. The ratio of iron to oxygen shows that the oxygen-carrying capacity is less.