cytochrome

/suy"teuh krohm'/, n. Biochem.

any of several carrier molecules in the mitochondria of plant and animal cells, consisting of a protein and an iron-containing porphyrin ring and participating in the stepwise transfer of electrons in oxidation reactions: each cytochrome alternately accepts and releases an electron at a slightly lower energy level in the order designated b, c₁, c, a, and a₃. Cf. electron transport.

[1895-1900; CYTO- + -CHROME]

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Any of a group of cell proteins (hemoproteins) that serve a vital function in the transfer of energy within cells.

Hemoproteins are linked to a nonprotein, iron-bearing component (a heme group), which can undergo the reversible oxidation-reduction reactions that yield energy for the cell. Cytochromes are subdivided into three classes depending on what wavelengths of light they absorb. At least 30 different cytochromes have been identified.

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▪ chemical compound

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

      Cytochromes are subdivided into three classes (a, b, c) depending on their light-absorption spectra. At least 30 different cytochromes have been identified; they are designated by letters or combinations of letters and numbers, such as cytochrome a₃, cytochrome c, and cytochrome B562. Cytochrome c is the most stable and abundant member of the class, and it has been the most thoroughly studied. See also cellular respiration.

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