Most oxygen is transported in the blood bound to which molecule or structure?

• A. Albumin in plasma
• B. Hemoglobin within erythrocytes
• C. Dissolved directly in plasma
• D. Bicarbonate ions $H_C{O}_3-$ in plasma

Answer: (B)

Verified step by step guidance

1. Understand that oxygen transport in the blood occurs primarily in two forms: bound to molecules within red blood cells or dissolved in plasma.
2. Recognize that hemoglobin is a protein found inside erythrocytes (red blood cells) that has a high affinity for oxygen, allowing it to bind oxygen molecules efficiently.
3. Recall that although some oxygen is dissolved directly in plasma, this amount is very small compared to the oxygen bound to hemoglobin.
4. Note that albumin is a plasma protein mainly responsible for maintaining osmotic pressure and does not significantly bind oxygen for transport.
5. Understand that bicarbonate ions (HCO\_3\^-) are involved in carbon dioxide transport, not oxygen transport.