OSMT (Ontario Society of Medical Technologists) Practice Exam

What is the oxygen-carrying protein of RBCs?

1. Prothrombin

2. Haemoglobin

3. Myoglobin

4. Erythropoietin

The correct answer is: Haemoglobin

The oxygen-carrying protein of red blood cells (RBCs) is hemoglobin. This protein is crucial for the transport of oxygen from the lungs to the tissues throughout the body. Hemoglobin binds to oxygen molecules due to the presence of iron in its structure, specifically at the heme group, which forms a complex with oxygen, allowing for efficient oxygen delivery. In addition to its primary function of oxygen transport, hemoglobin also plays a role in transporting carbon dioxide, a byproduct of metabolism, from the tissues back to the lungs for exhalation. The unique quaternary structure of hemoglobin allows it to undergo conformational changes, enhancing its capacity to pick up oxygen in the lungs and release it in tissues where it is needed most. Other options serve different roles: prothrombin is a protein involved in blood clotting, myoglobin is a similar oxygen-binding protein found in muscle tissues that helps store oxygen, and erythropoietin is a hormone that stimulates the production of red blood cells. Understanding the specific functions of these proteins and hormones clarifies why hemoglobin is distinguished as the primary oxygen-carrying component in red blood cells.