Final answer:
The statement (c) 'Heme with Fe2+ can bind O₂ reversibly' is true regarding heme. It correctly describes the heme's ability to transport oxygen in the blood through reversible binding with its central iron atom.
Step-by-step explanation:
The correct statement about heme is (c) Heme with Fe2+ can bind O₂ reversibly. Heme is an essential component of hemoglobin, the protein that transports oxygen in the blood. The heme group consists of a protoporphyrin ring with an iron (Fe2+) at its center. This iron ion can indeed bind oxygen molecules reversibly, meaning it can attach and release oxygen without altering the heme structure significantly. When oxygen binds, the iron ion changes its oxidation state momentarily as electron density transfers between the iron and oxygen, but this does not mean that the presence of Fe3+ is impossible or that oxygen becomes unreactive; therefore, statements (a), (b), and (d) are not correct. Heme can exist with Fe3+, but in this state, it cannot bind oxygen, which is key to its function in oxygen transport.