Which substance is primarily responsible for transporting oxygen in the blood?

• A. Hemoglobin within erythrocytes
• B. Bicarbonate ions in plasma
• C. Fibrinogen within platelets
• D. Albumin dissolved in plasma

Answer: (A)

Verified step by step guidance

1. Step 1: Understand the components of blood and their functions. Blood consists of plasma and formed elements, including erythrocytes (red blood cells), leukocytes (white blood cells), and platelets.
2. Step 2: Identify the role of erythrocytes. Erythrocytes contain hemoglobin, a protein specialized in binding and transporting oxygen molecules from the lungs to tissues throughout the body.
3. Step 3: Recognize the function of hemoglobin. Hemoglobin binds oxygen reversibly, allowing oxygen to be picked up in the lungs and released in tissues where it is needed.
4. Step 4: Differentiate other substances listed. Bicarbonate ions in plasma primarily transport carbon dioxide, fibrinogen within platelets is involved in blood clotting, and albumin dissolved in plasma helps maintain osmotic pressure but does not transport oxygen.
5. Step 5: Conclude that hemoglobin within erythrocytes is the primary substance responsible for oxygen transport in the blood.