What role does hemoglobin play in the respiratory system?

• A. Stores oxygen in muscles
• B. Binds oxygen in red blood cells, transporting it throughout the body
• C. Carries carbon dioxide to the lungs for removal
• D. Pumps oxygen through the bloodstream

Answer: (B)

Hemoglobin’s main job is to bind oxygen in the lungs and carry it through the bloodstream to tissues that need it. In the lungs, oxygen attaches to the iron in the heme groups of hemoglobin, forming oxyhemoglobin. As blood reaches tissues with lower oxygen, hemoglobin releases the oxygen where it’s used for cellular respiration to produce energy. This oxygen transport is the central function, enabling every cell to respire effectively. While hemoglobin does participate in carbon dioxide transport to some extent, most CO2 is carried back to the lungs in other forms (like as bicarbonate in plasma). The heart and blood vessels, not hemoglobin, are responsible for pumping oxygenated blood throughout the body. Storing oxygen in muscles is the job of myoglobin, not hemoglobin.