Which of the following natural substance contains iron (Fe)?

1. A

   Chlorophyll

   (a) Chlorophyll. The porphyrin of chlorophyll holds magnesium, not iron.

2. B

   Collagen

   (b) Collagen. Structural protein of connective tissue; it is not an iron metalloprotein.

3. C

   Keratin

   (c) Keratin. Hair and nail protein, sulphur-rich, without iron as a prosthetic metal.

4. D

   Myoglobin

   (d) Myoglobin. Muscle oxygen-store protein with a haem group whose metal is iron (Fe2+). That is the official key.

Summary. Official key is (d). Myoglobin contains iron in haem. Chlorophyll has magnesium; collagen and keratin are not iron proteins.