Which statement is true about carbon monoxide binding to hemoglobin?

Which statement is true about carbon monoxide binding to hemoglobin?

• A. CO binds to hemoglobin to form carboxyhemoglobin, reducing oxygen delivery
• B. CO binds to red blood cells to increase oxygen delivery
• C. CO binds only to myoglobin, not hemoglobin
• D. CO binding has no effect on oxygen delivery

Answer: (A)

Carbon monoxide binds to hemoglobin with a very high affinity, forming carboxyhemoglobin. This dramatically reduces the blood’s capacity to carry oxygen and also shifts the oxygen-hemoglobin dissociation curve to the left, making it harder for hemoglobin to release oxygen to tissues. The net effect is decreased oxygen delivery to tissues, even if blood oxygen levels appear normal. So the true statement is that CO binds to hemoglobin to form carboxyhemoglobin, reducing oxygen delivery. CO can bind to myoglobin as well, but the clinically important impact comes from its strong, competing binding to hemoglobin and the resulting impairment of oxygen transport and release.

Carbon monoxide binds to hemoglobin with a very high affinity, forming carboxyhemoglobin. This dramatically reduces the blood’s capacity to carry oxygen and also shifts the oxygen-hemoglobin dissociation curve to the left, making it harder for hemoglobin to release oxygen to tissues. The net effect is decreased oxygen delivery to tissues, even if blood oxygen levels appear normal. So the true statement is that CO binds to hemoglobin to form carboxyhemoglobin, reducing oxygen delivery. CO can bind to myoglobin as well, but the clinically important impact comes from its strong, competing binding to hemoglobin and the resulting impairment of oxygen transport and release.