What does cytochrome mean?
A cytochrome is any of a group of iron-containing proteins found in nearly all living cells, where they act as electron carriers in the chemical reactions that produce energy. Named for their colored, pigment-like quality, cytochromes contain a heme group whose iron atom alternates between two oxidation states, allowing electrons to pass along the transport chains of respiration and photosynthesis. The term is essentially laboratory language: it appears in biochemistry textbooks, research papers, and medical literature rather than everyday conversation, and it is almost always used with a specific designation such as cytochrome c, cytochrome b, or the drug-metabolizing cytochrome P450 enzymes. Because key cytochromes are conserved across virtually all aerobic organisms, they also serve biologists as molecular clocks for tracing evolutionary relationships. Understanding the word opens a window onto how cells harvest energy at the molecular level.
nounAny of a class of heme-containing proteins that serve as electron carriers in cellular respiration and photosynthesis.
- A heme-containing protein that transfers electrons as part of the respiratory or photosynthetic electron transport chain.
- (In compounds such as cytochrome P450) any member of the cytochrome family functioning in metabolic oxidation reactions.
"The enzyme cytochrome c oxidase catalyzes the final step of the electron transport chain in mitochondria."
"Mutations affecting cytochrome b have been widely used to study mitochondrial evolution."
"Liver cells rely on cytochrome P450 enzymes to metabolize many drugs and toxins."
The plural is standard when referring to multiple members of the class; in scientific writing the singular often appears within compound names such as 'the cytochrome c oxidase subunit'.
"Mitochondria contain several distinct cytochromes, each with a characteristic absorption spectrum."
Every oxygen-breathing organism on Earth — from bacteria to blue whales — relies on the same ancient molecule, cytochrome c, a molecular heirloom inherited from a single ancestor billions of years ago.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of cytochrome
The word cytochrome was coined in the 1920s by the Polish-born British scientist David Keilin, who rediscovered these pigments and established their role in cellular respiration; he later attributed the name to earlier observations of similar pigments. It combines two Greek roots: kytos, meaning 'hollow vessel' or 'cell', and chrōma, meaning 'color', reflecting the pigments' distinctive absorption spectra. The same roots recur throughout scientific vocabulary, from cytology and cytoplasm to chromosome and monochrome.
How cytochrome is actually used
Strictly technical vocabulary confined to biochemistry, cell biology, and medicine; it carries no figurative or informal use. In scientific writing it almost always appears with an identifying suffix (c, b, P450, oxidase).
Easily confused with cytochrome
A chromosome is a DNA-and-protein structure that carries genetic information in the cell nucleus, whereas a cytochrome is a protein involved in electron transfer during cellular respiration.
Cytosol is the fluid portion of the cytoplasm in which cell components are suspended, while a cytochrome is a specific type of protein.