Human Gas Exchange (Cambridge O Level Biology)

The diagram below shows a cross-section through an alveolus and a capillary.

Why does oxygen move from P to Q?

Some amphibians, such as frogs, can use their skin as a gas exchange surface.

What are the most likely characteristics of the surface of the skin in these amphibians?

When the diaphragm relaxes and internal intercostal muscles contract, how does the volume and pressure inside the thorax change?

Compared to the composition of atmospheric air, the air exhaled by a man contains:

The diagram shows the composition of four samples of air (O₂ = oxygen, CO₂ = carbon dioxide, N₂ = nitrogen).

Which sample is inspired air and which sample is expired air?

Why does oxygen enter the blood in the lungs?

Which of the following correctly describes the actions of the intercostal muscles and the diaphragm when we breathe in?

The diagram shows part of the structure of a human lung.

Where would the concentration of carbon dioxide be highest?

The diagram below illustrates the changes in air pressure taking place inside the lungs during a complete cycle of breathing. Atmospheric pressure is 101 kPa.

At which point on the diagram does the process of inhalation start?

A person exhales, and the air from their lungs is collected and placed in a gas jar. A second gas jar contains normal atmospheric air. A candle is set alight and is placed inside each gas jar as shown. The time taken for each flame to go out is measured with a stopwatch.

The table shows the results of this experiment.

Which of the following is a correct explanation for the difference between the results in jars 1 and 2?

Which of the following helps carbon dioxide to be excreted rapidly into the alveoli from the blood in the lungs?

1. Inhaled air has a lower concentration of carbon dioxide than the blood constantly pumping through the lungs.
2. Alveoli have thick walls and a large surface area.
3. Alveoli have thin walls and a large surface area.
4. The concentration of carbon dioxide in the blood is lower than in the alveoli.

The graph shows changes in the volume of air in the lungs of a person at rest, over a period of 30 seconds.

Which graph below shows the changes in the volume of air in the lungs for the same person immediately after they have done a few minutes of vigorous exercise?