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W.B.C.S. Examination Notes On – Cytochromes – Chemistry.
WBCS পরীক্ষার নোট – সাইটোক্রোম – রসায়নের ণোট।
Chemistry is one such optional offered in the W.B.C.S. Examination. It is one of the optional subjects that is preferred by the aspirants graduated with the subject. Chemistry optional is a scoring subject if aspirants have sound knowledge in it. Similar to other optional papers, chemistry also has two papers. The paper I of chemistry optional deals with Inorganic Chemistry and Physical Chemistry. Paper-II completely deals with Organic Chemistry.Following previous years question papers are a must when it comes to optional subjects.Cytochromes have been isolated from various types of microorganisms, and many of them are well characterized although their functions have not been completely elucidated.Continue Reading W.B.C.S. Examination Notes On – Cytochromes – Chemistry.
It has now been established that cytochrome functions in photosynthesis and in respiration, and that cytochrome exists in many anaerobic organisms and in all aerobic organisms. At present, cytochromes are classified into four types—A, B, C, and D—on the basis of the kind of the heme that they possess as the prosthetic group; A-type cytochrome or cytochrome A has heme a as the prosthetic group, cytochrome B protoheme IX, cytochrome C heme c, and cytochrome D heme d. Cytochrome mainly participates in the energy conversion processes of the organisms, that is, it works in respiration and photosynthesis.
In respiration or cellular respiration of aerobic organisms, electrons liberated from a substrate are transferred to molecular oxygen via a respiratory chain that is composed of cytochromes, flavin enzymes, and nonheme iron proteins, and the free energy liberated during the electron transfer is trapped as ATP, which is utilized by the organisms for life processes.Also Read ,Nernst Heat Theorem – Chemistry Notes – For W.B.C.S. Examination.
Prior to the immunological and amino acid sequence data, it was not clear whether the multiplicity of cytochrome P450 was due to genetically determined differences or epigenetic factors occuring after the polypeptide chain had been synthesized. From a comparison of the amino acid compositions and partial sequences of these proteins at both the N- and C-terminal ends, we can state that cytochromes P450a, P450b, and P450c have different primary structures. In addition, since antibodies are directed against several spatially distant sites on a protein surface, the absence of immunochemical relatedness indicates that these proteins have dissimilar tertiary structures.
Thus, the data presented argues strongly that cytochromes P450a, P450b, and P450c are separate gene products and not post-translational modifications of a single gene product. Alternatively, one would have to postulate extensive post-translational processing at both the N- and C-terminal ends as well as the removal of all antigenic sites and the exposure of a new set of immunological determinants. Until now, the various cytochromes P450 have been referred to as multiple enzyme forms. Our data clearly place cytochromes P450a, P450b, and P450c in the category of isozymes arising from unrelated genes. Isozymes in this class (10) catalyze the same enzymic reaction but do not necessarily have similar catalytic properties, are characterized by very different amino acid sequences and are immunochemically distinct due to different genetic makeup.
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