Which pollutant gas binds to hemoglobin much more strongly than oxygen?
2019
Which pollutant gas binds to hemoglobin much more strongly than oxygen?
Answer: B. Carbon monoxide — CONCEPTGases that compete for hemoglobin are judged by their binding affinity to the heme group, not by ordinary solubility. A gas with much higher affinity…
- A.
Carbon dioxide
- B.
Carbon monoxide
- C.
Nitric oxide
- D.
Hydrogen sulphide
Show answer & explanation
Correct answer: B
CONCEPT
Gases that compete for hemoglobin are judged by their binding affinity to the heme group, not by ordinary solubility. A gas with much higher affinity forms a stable hemoglobin complex and reduces oxygen transport.
APPLICATION
Carbon monoxide is an air pollutant produced by incomplete combustion. It forms carboxyhemoglobin and has about 200-250 times the affinity of oxygen for hemoglobin, so the gas that fits the stem is carbon monoxide.
CONTRAST
Carbon dioxide is mainly carried in blood through bicarbonate and carbamino forms; selecting it confuses normal carbon dioxide transport with pollutant-gas poisoning.
Nitric oxide is associated with biological signaling and heme interactions; selecting it mixes that role with the common air-pollutant toxicity fact tested here.
Hydrogen sulphide is toxic mainly through effects on cellular respiration enzymes; selecting it mixes a toxic-gas effect with a hemoglobin-transport fact.
RESULT
Carbon monoxide is the pollutant gas that binds hemoglobin much more strongly than oxygen.