Question

Read the following passage and answer the question that follow:

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

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

Hint:

Carbon monoxide competes with oxygen for the haem of haemoglobin.

Answer 1

Step 1: Read the graph:
Graph (Smoking Cigarette): nicotine in blood (mg/cm3) rises in a straight line from 0 at 1 minute to about 45 at 10 minutes, falls sharply to about 20 at 11 minutes, then falls slowly to about 10 at 15 minutes.
At 10 minutes the smoker is still taking 10 puffs per minute, so the smoke is still entering the lungs.

Step 2: Effect on carbon monoxide:
Cigarette smoke contains carbon monoxide (CO) along with nicotine and tar.
While smoking continues, CO is absorbed through the lungs into the blood. So the concentration of CO in the blood is highest at 10 minutes. It increases.

Step 3: Effect on haem-bound oxygen:
CO binds to the haem part of haemoglobin about 200 times more strongly than oxygen does. It forms carboxyhaemoglobin.
More haem sites are blocked by CO, so less oxygen can bind.
So the amount of haem-bound oxygen decreases and the blood carries less oxygen to the tissues.

Final Answer:
At 10 minutes, carbon monoxide in the blood increases and haem-bound oxygen decreases, because CO occupies haemoglobin in place of oxygen.