What is an example of a biochemical similarity between two different organisms?

An example of a biochemical similarity between two different organisms is the presence of cytochrome c, a protein involved in the electron transport chain, which is found in both humans and yeast. Despite the vast evolutionary distance between these organisms, the structure and function of cytochrome c are remarkably conserved. This similarity underscores the shared biochemical pathways that are fundamental to cellular respiration across diverse life forms, highlighting the common ancestry of all living organisms.