Final answer:
Cytochromes contain a metal ion that can accept and donate electrons, specifically the iron within the heme group of cytochrome c, which alternates between Fe³⁺ and Fe²⁺ states.
Step-by-step explanation:
The compounds that contain a metal ion which can accept and donate electrons are cytochromes. Cytochromes are a class of metalloproteins that are electron-transferring proteins, which contain metals such as iron within their structures. Specifically, the iron in the heme group of cytochrome c can alternate between Fe³⁺ and Fe²⁺ through the loss or gain of an electron, thus playing a pivotal role in electron transfer during cellular respiration. This ability is crucial for the function of cytochromes in the electron transport chain in the mitochondria, where they transfer electrons between different proteins embedded in the inner mitochondrial membrane. It is important to note that other items listed, such as fluorochromes, quinolones, and chelators, do not fit this category as they do not operate as electron-transferring metalloproteins.