12.1.3

Respirometers

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Respirometers

Respirometers can be used to investigate the rate of respiration.

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Using a respirometer

  • A respirometer is used to measure how much oxygen is used up in aerobic respiration by organisms like small insects or germinating seeds.
  • The organisms are put in an airtight container along with soda lime.
    • Soda lime absorbs the carbon dioxide the organisms produce.
  • When the organisms use up oxygen, the coloured liquid moves along the manometer.
  • This can be repeated to show the effect of temperature or other factors on the rate of aerobic respiration
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Calculating volume

  • To calculate the volume of oxygen used, you need to know the diameter of the capillary tube in the manometer.
  • You can then use the below formula to calculate the volume of oxygen used:
    • The volume of O2 = distance coloured liquid moves x πr2
    • Where "r" is the radius of the capillary tube.
  • The volume of oxygen used at different temperatures can be used to analyse the effect of temperature on respiration.
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Calculating respiratory quotients

  • To calculate respiratory quotients, two respirometers need to be set up.
    • One respirometer should not contain soda lime. This means any carbon dioxide produced is not absorbed.
  • The tube with soda lime (the experimental tube) will show the volume of oxygen consumed as above.
  • The tube without soda lime (the control tube) can be used to calculate the volume of CO2 produced. To do this:
    • Distance fluid moves in the experimental tube - distance fluid moves in the control tube.
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Calculating respiratory quotients 2

  • To calculate the respiratory quotient, divide the volume of carbon dioxide released by the volume of oxygen released.

Jump to other topics

1Cell Structure

2Biological Molecules

3Enzymes

4Cell Membranes & Transport

5The Mitotic Cell Cycle

6Nucleic Acids & Protein Synthesis

7Transport in Plants

8Transport in Mammals

9Gas Exchange

10Infectious Diseases

11Immunity

12Energy & Respiration (A2 Only)

13Photosynthesis (A2 Only)

14Homeostasis (A2 Only)

15Control & Coordination (A2 Only)

16Inherited Change (A2 Only)

17Selection & Evolution (A2 Only)

18Classification & Conservation (A2 Only)

19Genetic Technology (A2 Only)

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