Gaseous Exchange

The table below show the percentage composition of inhaled and exhaled air, in a

human being at rest and also the composition of exhaled air, during exercise. Use

the information in the table to answer the questions that follow.

Inhaled Air at rest Water vapour Nitrogen Carbon dioxide Oxygen
Variable 79% 0.03% 20.96%
Exhaled Air at rest 0.8% 79% 4.1% 16.2%
Exhaled Air during exercise 0.92% 79% 4.5% 15.5%



(a) State the differences in composition between inhaled and exhaled air at rest

(b) Give a reason for each difference stated in (a).

(c) State the changes that occur in the composition of exhaled air in a human who is previously at rest, then takes an exercise.

(d) Give a reason why each change stated in (c) occurs.

(e) During exercise, the breathing rate increase. From the information provided,

suggest why this happens.

(f) Why is the percentage of nitrogen constant in inhaled and exhaled air?

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