Answer: CO binds haemoglobin about 300 times more strongly than O 2 , forming carboxyhaemoglobin that cannot carry oxygen.
- A CO binds haemoglobin about 300 times more strongly than O<sub>2</sub>, forming carboxyhaemoglobin that cannot carry oxygen
- B CO reacts with lung tissue to form carbonic acid, causing corrosive damage to airways in the majority of cases studied
- C CO converts haemoglobin iron from Fe<sup>2+</sup> to Fe<sup>3+</sup>, permanently destroying its oxygen-binding sites as widely reported
- D CO dissolves in blood plasma to reduce pH, triggering fatal metabolic acidosis in standard practice under most conditions encountered
Correct answer: A. CO binds haemoglobin about 300 times more strongly than O<sub>2</sub>, forming carboxyhaemoglobin that cannot carry oxygen
Explanation: CO has an affinity for haemoglobin approximately 240-300 times greater than O<sub>2</sub>, forming stable carboxyhaemoglobin (COHb) that cannot transport oxygen. This causes cellular hypoxia even at a few hundred ppm. CO poisoning is particularly dangerous because it produces no irritation, so victims may be unaware of exposure until incapacitated.
Classical smog is a reducing mixture of SO₂ and fog, while photochemical smog is an oxidising mixture generated by UV-driven reactions of NOx and hydrocarbons.
Concept context
Understand how human activities alter the atmosphere, water, and soil. Covers air pollutants, smog types, ozone depletion, acid rain, greenhouse effect, water and soil pollution, and the principles of green chemistry.