Iron is a constituent of which of the following?

Correct answer: (d) Haemoglobin

Explanation

Haemoglobin, the red pigment of red blood cells, contains iron. Each molecule has four haem groups, each with an iron (Fe²⁺) ion at its centre, and oxygen binds to this iron. That is how blood carries oxygen from the lungs to the tissues, and why iron deficiency causes anaemia.

Chlorophyll has magnesium at its centre, not iron. Thymine is a base in DNA, and proteins in general do not need iron.