Which protein is the primary oxygen-carrying component of red blood cells?

• A. Hemoglobin
• B. Myoglobin
• C. Fibrinogen
• D. Albumin

Answer: (A)

Oxygen transport in blood hinges on a protein that can reversibly bind oxygen as it travels from lungs to tissues. Hemoglobin fits this role perfectly because it’s a iron-containing protein inside red blood cells that binds oxygen in the lungs and releases it where it’s needed. Each hemoglobin molecule can carry up to four oxygen molecules, enabling efficient, widespread delivery throughout the body. That makes it the primary oxygen-carrying component of red blood cells.

In contrast, myoglobin stores oxygen in muscle tissue and doesn’t serve as the main transporter in blood. Fibrinogen is a clotting factor involved in forming fibrin during coagulation, not oxygen transport. Albumin helps maintain blood volume and transports various substances but does not carry oxygen.