Question

The data below shows the concentration of nicotine smoked by a smoker taking 10 puffs/minute.

Graph: "Smoking Cigarette" - concentration of nicotine in blood (mg/cm³) plotted against time (minutes).

(ii) How will this affect the concentration of carbon monoxide and haem-bound oxygen at 10 minutes ?

Hint:

Smoke carries CO, and CO binds haemoglobin far more strongly than oxygen, so CO goes up and haem-bound oxygen goes down.

Answer 1

Step 1: Recall what cigarette smoke carries:
Cigarette smoke contains nicotine and also carbon monoxide (\(\mathrm{CO}\)). At 10 minutes the nicotine level is at its peak, so the smoker has been inhaling smoke continuously.
This means a lot of \(\mathrm{CO}\) has also been inhaled by this time.

Step 2: Effect on carbon monoxide:
\(\mathrm{CO}\) passes from the lungs into the blood. So the concentration of \(\mathrm{CO}\) in the blood is high at 10 minutes.

Step 3: Effect on haem-bound oxygen:
\(\mathrm{CO}\) binds to the haem part of haemoglobin about 200 times more strongly than oxygen does. It forms carboxyhaemoglobin.
Once the haem sites are taken by \(\mathrm{CO}\), less oxygen can attach. So the amount of haem-bound oxygen goes down.

Step 4: Result for the body:
Tissues then get less oxygen. The heart and muscles have to work harder to make up for it.

Final Answer:
At 10 minutes the carbon monoxide level in blood increases and the haem-bound oxygen decreases, because \(\mathrm{CO}\) occupies haemoglobin in place of oxygen.