Which one of the following is required both by the process of respiration and photosynthesis?

The cytochromes are proteins with the characteristic strong absorption of visible light, due to their iron containing heme prosthetic groups. They are an essential electron transport component of both mitochondria and chloroplast. In mitochondria and chloroplasts, these cytochromes are often combined in electron transport and related metabolic pathways.

So, the correct answer is option D.