Gas exchange

In humans, gas exchange occurs in the alveoli of the lungs.

Figure 9 shows the structure of an alveolus and its blood supply.

Which process moves carbon dioxide from the blood into the alveolus?

State one adaptation of an alveolus that increases the rate of gas exchange.

Describe how blood is moved from the heart to the lungs.

Figure 10 shows the heart rate of a person before, during and after exercise.

Describe the trend shown in Figure 10.

Use data from Figure 10 to support your answer.

Explain the trend shown in Figure 10 from 5 minutes to 25 minutes.

The stroke volume is the volume of blood pumped during one beat of the heart.

At 25 minutes the stroke volume was 0.13 dm³.

Calculate the cardiac output of the heart of this person at 25 minutes.

Use the equation

cardiac output = stroke volumeheart rate

_........ dm³ per minute

Gas exchange happens in the alveoli in the lungs.

Figure 12 shows an alveolus and a capillary.

(adapted from: sciencepics/shutterstock)

Figure 12

Name the gas used in respiration that moves from the alveolus into the capillary.

Name the gas produced by respiration that moves from the capillary into the alveolus.

The capillary wall is only one cell thick.

Explain how gases move from the alveolus to the capillary.

Explain the advantages of red blood cells passing one at a time through this narrow capillary.

The average number of alveoli in each human lung is 280 million.

The surface area of 1 million alveoli is 0.25 m².

Calculate the total surface area of a human lung.

Figure 18 shows ciliated epithelial cells from the airways of a human as seen using a light microscope.

Draw the cell labelled A in the box below.

Label three parts of this cell on your diagram.

State the function of the ciliated epithelial cells in the airways of the human breathing system.

Figure 19 shows equipment used to investigate the rate of respiration in maggots.

As the maggots respire, the drop of coloured liquid moves towards the test tube.

Figure 20 shows the position of the drop of coloured liquid after ten minutes.

Use information from Figures 19 and 20 to calculate the mean rate of respiration of the maggots in mm per minute.

*(c) Explain how alveoli in human lungs are adapted for gas exchange.

Include the names of the gases that are being exchanged.

(a) Figure 10 shows alveoli from a lung.

Figure 10

Explain why these alveoli have the internal structure shown in Figure 10.

How does oxygen move across the alveolar membrane into the capillary?

Figure 11 shows the movement of molecules across a membrane.

at start
after 2 seconds
after 4 seconds

Figure 11

Describe how Figure 11 illustrates movement of molecules across a membrane.

*(c) Explain, using Fick’s law, the factors that affect the diffusion rate of molecules into and out of cells.

Figure 2 shows alveoli from a healthy lung.

Smoking can cause a condition called emphysema.

Figure 3 shows alveoli from a person with emphysema.

Use words from the box to complete the following sentences.

breathing diffusion larger

osmosis smaller thicker

The alveoli from the person with emphysema have a_........

surface area than the alveoli from a healthy lung.

The surface area of the alveoli will affect how much oxygen moves into the blood

The graph in Figure 4 shows the volume of oxygen an athlete absorbs at different running speeds.

Describe the trend shown in Figure 4.

Which uses more oxygen when the running speed of the athlete changes from 4 to 6 km per hour?

Explain why the athlete produces lactic acid when running at 14 km per hour.