Hemoglobin is best described as which?

• A. Protein carrying oxygen
• B. Neutral antibody
• C. Enzyme that digests fats
• D. Protein that transports carbon dioxide only

Answer: (A)

Hemoglobin’s main job is to shuttle oxygen in the blood. It’s a protein in red blood cells with heme groups containing iron that bind oxygen reversibly, allowing up to four O2 molecules to be carried from the lungs to tissues where they are needed for cellular respiration. This oxygen transport is the defining function. Hemoglobin does help move carbon dioxide back to the lungs as part of its cycle—through carbaminohemoglobin and via bicarbonate in plasma—but this is a secondary role and not its sole purpose. It isn’t an antibody and isn’t an enzyme that digests fats, so those descriptions don’t fit.