Carbon monoxide binds to which molecule in the blood, reducing oxygen delivery to tissues?

Carbon monoxide binds to which molecule in the blood, reducing oxygen delivery to tissues?

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

Answer: (C)

Carbon monoxide binds to hemoglobin, the protein in red blood cells that carries oxygen. CO sticks to the iron in the heme group far more strongly than oxygen does, forming carboxyhemoglobin. This blocks oxygen from binding and also makes the remaining oxygen-binding sites hold on to oxygen more tightly, so less oxygen is released to tissues. Other listed substances aren’t the main oxygen carrier in the blood—myoglobin is in muscles, not the circulating transporter, and albumin and fibrinogen have roles in transport and clotting, not oxygen delivery.

Carbon monoxide binds to hemoglobin, the protein in red blood cells that carries oxygen. CO sticks to the iron in the heme group far more strongly than oxygen does, forming carboxyhemoglobin. This blocks oxygen from binding and also makes the remaining oxygen-binding sites hold on to oxygen more tightly, so less oxygen is released to tissues. Other listed substances aren’t the main oxygen carrier in the blood—myoglobin is in muscles, not the circulating transporter, and albumin and fibrinogen have roles in transport and clotting, not oxygen delivery.