Question

Which of the following gases makes the most stable combination with the haemoglobin of red blood cells?

• A. ${CO}_2$
• B. $CO$
• C. $O_2$
• D. $N_2$

Answer 1

The correct option is B $CO$

• The combination of oxygen with haemoglobin is called oxyhaemoglobin and this oxygenated blood is carried away from the lungs through the bloodstream to all the tissues of the body.
• Carbon monoxide can also bind to haemoglobin but does so about 240 times more tightly than oxygen, forming a compound called carboxyhaemoglobin.
• This means that if both carbon monoxide and oxygen are inhaled, carbon monoxide will preferentially bind to haemoglobin.
• This reduces the amount of haemoglobin available to bind to oxygen, so the body and tissues become starved of oxygen.