Which gas is primarily transported by hemoglobin?

• A. Carbon dioxide
• B. Oxygen
• C. Nitrogen
• D. Hydrogen

Answer: (B)

Hemoglobin is a protein found in red blood cells that plays a crucial role in gas transport throughout the body. It has a high affinity for oxygen, allowing it to effectively pick up oxygen from the lungs and deliver it to tissues and organs that require it for cellular respiration. The structure of hemoglobin consists of four heme groups, each capable of binding to one molecule of oxygen. This ensures that hemoglobin can carry up to four molecules of oxygen at a time.

While hemoglobin can also transport carbon dioxide, it primarily functions to transport oxygen. In the context of the other options, nitrogen is typically dissolved in the blood plasma rather than being carried by hemoglobin, and hydrogen does not play a role in gas transport in the same way that oxygen and carbon dioxide do. Therefore, the correct response highlights the primary function of hemoglobin as an oxygen transport molecule, which is vital for sustaining human life by facilitating respiration and energy production in cells.