Cytochromes P450 are proteins of the superfamily containing heme as a cofactor and, therefore, are hemeproteins. CYPs use a variety of small and large molecules as substrates in enzymatic reactions. They are, in general, the terminal oxidase enzymes in electron transfer chains, broadly categorized as P450-containing systems. The term "P450" is derived from the spectrophotometric peak at the wavelength of the absorption maximum of the enzyme (450 nm ) when it is in the reduced state and complexed with carbon monoxide. Most CYPs require a protein partner to deliver one or more electrons to reduce the iron (and eventually molecular oxygen). Depending on the substrate and enzyme involved, P450 enzymes can catalyze any of a wide variety of reactions. A hypothetical hydroxylation is shown in this illustration. After the product has been released from the active site, the enzyme returns to its original state, with a water molecule returning to occupy the distal coordination position of the iron nucleus. So the correct option is 'it is a coloured cell.