Which single - celled organism is used in the experiment? (can respire aerobically and anaerobically)
Yeast
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How can the rate of respiration be measured?
Using a redox indicator dye such as methylene blue - accepts electrons that would usually be transferred to synthesise ATP in oxidative phosphorylation. Or measuring increase in volume of CO2/decrease in O2.
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What represents the rate of respiration?
Time taken for methylene blue to turn colourless (turns colourless when reduced) - shorter time = faster rate of respiration.
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What could be tested as the independent variable? (factors affecting the rate of respiration (4)
1) Temperature 2) pH 3) O2 concentration 4) Type of sugar
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Why should the yeast and glucose solution be buffered?
To maintain a constant pH - changes in pH could affect enzymes involved in respiration, affecting the rate.
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What should be controlled? (depends on the independent variable)
Yeast solution concentration, concentration of sugar solution, temperature, pH.
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What can be used to indicate whether conditions inside the test tube are aerobic or anaerobic?
Indicator that changes colour in the presence/absence of oxygen.
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Why might a layer of oil be transferred to the top of the yeast solutions if anaerobic conditions are being tested?
To ensure that no oxygen can diffuse into the yeast cells from the atmosphere.
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Why should the test tube(s) be left in the water bath for a few minutes before closing the clip?
To ensure that the temperature of the yeast solution equilibriates with that of the water bath.
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Why should the spring clips be left open for a few minutes before starting the experiment?
To allow the pressure in the apparatus to equilibriate with atmospheric pressure.
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What should be done before the fluid in the capillary tube begins to move?
The position of it's should be marked - so that the distance that it has travelled can be measured at the end of the experiment.
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What could be measured instead of distance moved by the fluid in the capillary tube?
Time taken to move a set distance (a 2nd line could be marked on the capillary tube a set distance from the initial line and time taken for fluid to reach 2nd line recorded).
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Why should the clip be loosened after each experiment?
To allow air into the apparatus so that the meniscus falls back to its original level.
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What risk might yeast pose?
May be an allergen.
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Other cards in this set
Card 2
Front
How can the rate of respiration be measured?
Back
Using a redox indicator dye such as methylene blue - accepts electrons that would usually be transferred to synthesise ATP in oxidative phosphorylation. Or measuring increase in volume of CO2/decrease in O2.
Card 3
Front
What represents the rate of respiration?
Back
Card 4
Front
What could be tested as the independent variable? (factors affecting the rate of respiration (4)
Back
Card 5
Front
Why should the yeast and glucose solution be buffered?
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