Question

Cytochromes are
A. Glycoproteins
B. Lipids
C. Fe⁺⁺ containing porphyrin pigments
D. Metalloporphyrins

Answer 1

Hint:
Cytochromes are proteins comprising a heme, with a central Fe atom at their core as a cofactor. They are involved in oxidation-reduction reactions and the electron transport chain. They are categorized according to the type of heme and its way of binding. Four types of cytochromes are cytochromes a, cytochromes b, cytochromes c, and cytochrome d.

Complete step by step answer:
The function of cytochrome is linked to the reversible redox change from the ferrous to the ferric oxidation state of the iron located in the heme centre. The heme group is a highly conjugated ring system (which permits its electrons to be mobile) encircling an iron ion. The iron in cytochromes usually exists in a Fe⁺⁺ and a Fe⁺⁺⁺ state, with a Fe⁺⁺⁺⁺ state in catalytic intermediates. So cytochromes can perform the oxidation-reduction reaction of their heme iron and electron transfer reactions. The location of cytochromes in cells depends on their function. They can be seen as membrane proteins or globular proteins.
Metalloporphyrins are heme oxygenase inhibitors that act in the pathway of heme degradation leading to the production of bilirubin. Glycoproteins are the class of proteins in which the oligosaccharide chains are covalently attached to the amino acid side chains. Lipids are a broad group of naturally-occurring molecules that include waxes, fats, sterols, fat-soluble vitamins, phospholipids, monoglycerides, diglycerides, etc.

Option ‘C’ is correct

Note:
Cytochrome a contains a prosthetic group as heme A, cytochrome b contains heme B, cytochrome c contains heme C, and cytochrome d contains heme D. Cytochrome e is not there, but cytochrome f, can be seen in the cytochrome b6f complex of plants, which is a c-type cytochrome.