Final answer:
Complex IV has a prosthetic group consisting of two heme groups and three copper ions, which are crucial for its role in the electron transport chain of cellular respiration.
Step-by-step explanation:
The prosthetic group that Complex IV has is composed of two heme groups and three copper ions. These are essential components for the complex's function within the electron transport chain, particularly for the reduction of oxygen to water.
In Complex IV, the heme groups are present in the cytochrome proteins a and a3, and the three copper ions consist of a pair of CuA and one CuB in cytochrome a3. The cytochromes, alongside copper ions, hold an oxygen molecule very tightly until it is completely reduced.