Respiration (AQA GCSE Biology: Combined Science)

The cells of animals require cellular energy.

Write a balanced chemical equation for aerobic respiration in animals.

Identify three different ways in which animals use the energy released by aerobic respiration.

In the absence of sufficient oxygen, cells respire anaerobically.

Compare anaerobic respiration in the muscle cell of an animal with anaerobic respiration in a yeast cell.

A student reads the following statement in a textbook:

‘Respiration and metabolism are linked to temperature.’

Explain why this statement is true.

Describe what happens to the products of respiration during the manufacture of bread.

In animals, exercise cannot be sustained with anaerobic respiration.

Explain why.

Describe and explain the changes that occur in the body during exercise.

A group of athletes carried out a 9-month training programme.

Figure 1 shows the effect of the same type and amount of exercise on one of the athlete’s heart rate before and after the training programme.

Figure 1

Calculate the percentage change in the athletes heart rate 10 minutes after the start of exercise.

Show your working.

The volume of blood pumped out of the left side of the heart in one beat is the stroke volume.

Figure 2 shows the relationship between the athlete's stroke volume and heart rate in beats per minute both before and after completing the training programme.

Figure 2

The cardiac output of the heart can be calculated by:

cardiac output = heart rate × stroke volume

Calculate the difference in cardiac output of the athlete 20 minutes after the start of exercise before and after the training programme. 

Show clearly how you calculated your answer.

Figure 1 shows that the heart of the athlete after completing the training programme beats more slowly than before the training programme.

Use information from Figure 2 to explain why.

Explain how an increased cardiac output helps the athlete to maximise their performance.

The bar chart in Figure 1 shows what happens in an athlete's muscles when running a 200 m race and a 3000 m race.

Figure 1

Compare what happens in the athlete's muscles when running in the two races.

Explain the differences measured in the muscles of the athlete as shown in Figure 1.

A woman completes a 100 m sprint.

Figure 2 shows the woman's heart rate before, during and after the race.

Figure 2

Explain why the woman's heart rate does not return to the resting heart rate as soon as she finishes the race.

The same woman runs a 400 m race.

Towards the end of the race, her muscles become fatigued and stop contracting efficiently.

Suggest an explanation as to why.

Higher Tier Only

Outline the role the liver plays in helping the athlete recover from vigorous exercise.

The continual enzyme-controlled processes of metabolism involve chemical reactions that synthesise new molecules and break down others in our bodies.

Describe some of these reactions.

Compare the processes of aerobic and anaerobic respiration in animals.

During exercise, the rate of respiration in muscle cells increases significantly.

To facilitate this, muscle cells are observed to contain many mitochondria.

Explain this observation.

Write the balanced chemical equation for respiration

[2 marks]

Some scientists wanted to investigate respiration rates in different areas of a plant. 

They measured carbon dioxide production in the roots and leaves of a plant at night time. 

Table 1 shows the rate of carbon dioxide production that they measured.

The carbon dioxide readings shown in Table 1 were all taken during the night time.

In order to collect the data about carbon dioxide produced by the roots of the plant, scientists took samples of the air from the soil around the plant roots and adjusted it to account for atmospheric carbon dioxide levels.

Figure 1 shows the oxygen and carbon dioxide composition of inhaled air and exhaled air from the lungs.

The data in Table 2 shows the distribution of blood to different organs of the body before and after exercise.

Table 2

Explain the reason for the changes in distribution of blood to the arteries of the heart and muscles of the skeleton, as shown in Table 2.

[5 marks]

The largest increase in blood flow during exercise is to the muscles of the skeleton where blood flow is 11 x faster than at rest.

Plan an investigation to test the effect of exercise on heart rate.

You should include the following variables in your method:

• The independent variable
• The dependent variable
• A control variable

Some scientists carried out the investigation described in part (a) but also decided to monitor the skin temperature of the athletes throughout the investigation.

The graph in Figure 2 shows the results collected for one student.

Figure 2

Between minutes 7 and 11 on Figure 2, the heart rate returns to resting rate.

Higher Tier Only

Figure 3 shows the results they collected from a study group in the post exercise recovery phase

Higher Tier Only

In serious cases of cirrhosis, patients may suffer complete liver failure.

A student used the equipment shown in Figure 4 to investigate the rate of anaerobic respiration in yeast.

Figure 4

The student measured the volume of carbon dioxide produced by 5 g of yeast over a 60 minute period. His results are shown in Table 3.

Table 3

Explain the importance of the role respiration plays in thermoregulation.

[4 marks]