How do red blood cells carry oxygen through the body?
Quick Answer
Red blood cells use hemoglobin, a protein that binds oxygen in the lungs and releases it in tissues. A healthy adult has about 20–30 trillion red blood cells.
The Full Story
Red blood cells carry oxygen because they are packed with hemoglobin, the iron-containing protein that binds oxygen in the lungs. In the pulmonary capillaries, hemoglobin picks up oxygen from inhaled air, then delivers it through the bloodstream to tissues that need energy. Most adult red blood cells live about 120 days before being broken down and replaced in the bone marrow. Their biconcave shape gives them a large surface area and helps them squeeze through tiny capillaries. This design makes them highly efficient oxygen transporters.
Key Facts
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