Respiration (Edexcel IGCSE Science (Double Award): Biology)

Which of these is the balanced chemical symbol equation for aerobic respiration?

A student uses this apparatus to investigate aerobic respiration in a locust.

(i) The coloured water drop moves during the investigation. 

Explain why the coloured water drop moves during the investigation.

(2)

(ii) The student compares the aerobic respiration of male and female locusts.

He uses three male locusts and three female locusts.

He uses locusts of the same age and the same species.

Explain three other variables that the student needs to control.

(6)

The table shows the student's results.

(i) Complete the table by giving the missing mean value.

(1)

(ii) Comment on the reliability of the data in the table.

(3)

A student reads the following statement in a textbook:

‘Respiration and metabolic reactions are intrinsically linked to temperature.’

Explain why this statement is true.

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

Compare the processes of aerobic and anaerobic respiration in animals.

In animals exercise cannot be sustained for long periods by anaerobic respiration.

Explain why this is the case.

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 used the equipment shown in the diagram to investigate the rate of anaerobic respiration in yeast.

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

Rate can be calculated using the following equation:

Use the equation to calculate the average rate of carbon dioxide production per minute between 30 and 60 minutes in the investigation.

Suggest why the rate of carbon dioxide production shown in part (b) decreased between 50 and 60 minutes.

Explain how the student could have ensured the reliability of the results.

Write the balanced symbol equation for respiration

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. 

The table shows the rate of carbon dioxide production that they measured.

Calculate the percentage difference in carbon dioxide production in the leaves compared to the roots.

The carbon dioxide readings shown in the table in part (b) were all taken during the night time.

Suggest a reason for this.

Suggest an explanation for the results shown in the table in part (b).

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.

Suggest why the readings they took may still be higher than the actual rate of carbon dioxide production in the plant roots.

Give a definition of the term 'respiration'.

In an investigation, a person ran at different speeds. 

The graph shows the concentration of lactic acid in the runner's blood and the runner's heart rate (in beats per minute) during the run. 

When the running speed is 22 km h^-1, the stroke volume of the runner is 0.18 dm³.

Calculate the cardiac output of the runner using the equation. State the appropriate units. 

Referring to the data in the graph in part (b), state the concentration of lactic acid in the blood when the heart rate has reached its maximum level. 

Explain why the concentration of lactic acid changes at running speeds greater than 18 km h^-1.

Once the person has finished running they begin their recovery. 

(i) Explain the changes that occur in the lactic acid levels during their recovery. 

(3)

(ii) Describe and explain how this process differs between fit people and unfit people. 

(3)

The image shows three respirometers set up for an investigation into respiration in peas. 

• Respirometer A contained germinating peas.

• Respirometer B contained peas that had been boiled and cooled before the experiment. 

• Respirometer C contained glass beads.

All other aspects of each respirometer were kept constant. 

All three respirometers were placed in a water bath at 25°C for 30 minutes. The reduction in oxygen levels inside each respirometer was measured using a data logger. 

Explain why the respirometers were placed in a water bath at 25°C for 30 minutes.

The scientist carrying out the study recorded the change in oxygen levels within the 3 respirometers over a 30-minute period. 

The results are shown below

A  10 minutes (-0.8) cm³, 20 minutes (-1.6) cm³, 30 minutes (-2.4) cm³

B  10 minutes (-0.1) cm³, 20 minutes (-0.1) cm³, 30 minutes (-0.1) cm³

C  No change

Draw a table to show these results. 

Calculate the rate of oxygen consumption per second for the peas in Respirometer A.

Include the units in your answer.

(i) Explain why glass beads were used in Respirometer C.

(1)

(ii) Explain why Respirometer A has the highest rate of oxygen consumption of the three respirometers.

(2)

The student wanted to adjust this investigation to measure the heat given off by respiration in germinating peas.

Design an investigation to find out if germinating peas release heat energy from respiration.  

Your answer should include experimental details and be written in full sentences.