Question

Cytochrome is a?
A. Mg pyrole ring
B. Fe porophyrin ring
C. Neucleotide
D. Alloy of Nichorme

Answer 1

Hint: In 1884, Cytochromes were initially described by the scientist MacMunn as a respiratory pigment (histohematin or myohematin). These are involved in the redox catalysis and electron transport chain.

Complete answer:
Cytochrome is a group of hemoprotein cell components which serve a vital function in the transfer of energy within cells, by readily undergoing oxidation and reduction (loss and gain of electrons) with the aid of enzymes. Hemoproteins are the proteins linked to an iron bearing non-protein component. It is the iron or heme group attached to protein which can undergo reversible reduction and oxidation reactions, thereby functioning as the electron carriers within mitochondria ( these are the organelles which produce energy for the cell through cellular respiration).

They are either found as monomeric proteins that are the cytochrome c or as the subunits of bigger enzymatic complexes which catalyze the redox reactions. They are found in mitochondrial inner membranes and endoplasmic reticulum of eukaryotes, in chloroplasts of plants, in bacteria and in photosynthetic microorganisms.

Cytochromes are again divided into three classes (a, b and c) depending on the light-absorption spectra. At least 30 different cytochromes have been identified till now. Cytochrome c is the most abundant and stable member of the class.

Hence, the correct answer is option (B).

Note: A completely distinct family of cytochromes is called cytochrome P450 oxidases. It was named for the characteristic Soret peak formed by the absorbance of light at wavelengths near 450 nm when the heme iron is reduced (with the sodium dithionite) and complexed to the carbon monoxide. These enzymes are primarily involved in steroidogenesis and detoxification.