Cytochrome

Cytochromes are haemoproteins (or proteins containing haem groups). They make ATP by electron transport.

They are found either as single (monomeric) proteins (e.g., cytochrome c) or as part of bigger enzyme complexes which catalyze redox reactions.

The haem group does the redox reactions. These include all chemical reactions in which atoms have their oxidation state changed. In general, redox reactions involve the transfer of electrons.

 History 
Cytochromes were described in 1884 as respiratory pigments. They include (haemoglobin, myoglobin, haemocyanin, haemoerythrin and  chlorocruorin.A respiratory pigment increases the oxygen-carrying ability of the blood. In the 1920s, Keilin rediscovered these respiratory pigments. He called them the cytochromes, or “cellular pigments”, and classified them as haem proteins.

 Types 
Several kinds of cytochrome exist and can be distinguished by spectroscopy. Three types of cytochrome are distinguished by their prosthetic groups.Prosthetic group  = add-on bit which makes it work
In mitochondria and chloroplasts, these cytochromes are often combined in electron transport and related metabolic pathways.

 References 

Category:Iron compounds
Category:Organometallic chemistry