Influence of yeast concentration on rate of cellular respiration

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Gracja Kowalska      kl.2  IB                 01-24-2009



Investigation how the difference in yeast concentration influence the rate of cellular respiration, during the reaction of respiration which product was ethanol and carbon dioxide.


If the yeast concentration is increased, then the amount of CO2 emitted will increase. This is because more yeast are able to produce ATP through cellular respiration. The more yeast are available, the faster the rate of cell respiration, and the more C02 that will be produced. This means the higher the concentration of yeast, the less time is needed to produce the same amount of CO2.

Control of variables:

The temperature was checked every 30 s during a measurement. No changes in the surrounding were made in order to keep the temperature stable. When the temperature was falling, the solution was heated up using burner until the initial temperature (40ºC) was reached. The acceptable change in the temperature was ± 0.05 ºC.

The amount of CO2 produced was kept the same through having the same distance of 5 cm in the manometer tube, as only the same amount of CO2 would move through that distance. The time has been measured since agreed level in the manometer tube was reached, in order to avoid the paralax effect.

Mass of sugar and solution was controlled by using weighting machine and by keeping the same mass of each solution for different yeast concentration.

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  • Yeast (20g)
  • Sugar (8 g)
  • Water (52 g= 52 cm3)
  • Termometer (0-110 ºC ±0.05 ºC)
  • Weighting machine (±0.05 g)
  • Razor blade
  • Boiling tubes (20.0±0.5 cm3)
  • Stand, bosses and clamps
  • Manometer tube
  • Clip
  • Clock (±0.1 s)
  • Pipettes (2.00±0.05 ml)


Precaution, razor blade is a sharp apparatus.


  1. Prepare solutions acorrding to data in Table 1 so in each case you have 20 g of solution.
  2. Construct the apparatus shown on the Drawing 1 using manometer and boiling tube.
  3. As only the influence of yeast concentration ...

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