aerobic and anaerobic respiration

When a living thing, such as yeast, respires it produces heat. It may do this in the presence or absence of oxygen. These processes are called aerobic respiration and anaerobic respiration. How would the yeast behave in these two situations?
To find out you can use temperature sensors to measure the heat produced. This is best done in a vacuum flask to prevent any loss of heat. You also need two flasks, one where the yeast can respire in air, the other where the yeast is without air and covered with oil.
What you need
Two vacuum flasks, cotton wool, yeast, sugar, oil, interface, temperature sensors.

Connect two temperature sensors to the interface.
Make a yeast suspension and divide it equally between two vacuum flasks.
Put a temperature probe each flask. If the sensor has a range control use a suitable range, for example from 0-40 degrees. Start the sensing software and see that it recognises the sensors you attach.
Set up the software to record for 24 hours. Or use the interface’s data logging feature where you press a button to get it to take readings without the computer.
Add an equal quantity of sugar to each flask.
Pour a layer of oil into the ‘anaerobic respiration’ flask. Loosely plug with cotton wool.
You may get results sooner than expected


  • How do you know that the yeast is respiring?
  • What do the shape of the graphs tell you about the progress of respiration?
  • How can you tell which flask showed the most respiratory activity?
  • If you recorded for twice as long how would the graph look?

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