Anaerobic Respiration in Yeast

This practical lesson covers:

  1. The role of anaerobic respiration by yeast in different conditions by counting the number of carbon dioxide bubbles produced in 1 minute.

Investigating the anaerobic respiration of yeast.


Aim:

To investigate the role of anaerobic respiration by yeast in different conditions by counting the number of carbon dioxide bubbles produced in 1 minute. 

Background information:

Anaerobic respiration in yeast involves converting sugars into energy, carbon dioxide, and alcohol in the absence of oxygen. This practical investigates how temperature affects this process by measuring CO2 bubble production in a controlled setup, where yeast ferments a sugar solution under an oil layer that blocks air. You will adjust the water bath temperatures to explore the impact of environmental conditions on yeast activity.

Variables:

  1. Independent variable - Temperature of the water bath.
  2. Dependent variable - Number of carbon dioxide bubbles produced in 1 minute.
  3. Control variable - Volume of sugar solution, mass of yeast, duration of each test.

Equipment:

  1. Boiling tube
  2. Test tube
  3. Yeast
  4. Sugar solution
  5. Oil
  6. Limewater
  7. Beaker
  8. Bunsen burner / thermostatically controlled water bath
  9. Delivery tube
  10. Digital mass balance

Method:

  1. Measure a fixed volume of sugar solution and add to the boiling tube.
  2. Place the boiling tube into a water bath for 5 minutes.
  3. Weigh a fixed mass of yeast and add to the boiling tube.
  4. Add a small quantity of oil to cover the top of the solution to prevent air from entering the solution.
  5. Use a delivery tube and a bung to connect the boiling tube to another test tube half-filled with limewater. Start timing immediately.
  6. Count the number of bubbles produced in 1 minute and record in a table.
  7. Repeat steps 1-6 twice and take a mean number of bubbles.
  8. Repeat steps 1-7 at a range of different water bath temperatures.

What is the role of anaerobic respiration by yeast?

converting sugars into energy, carbon dioxide, and alcohol in the presence of oxygen

converting sugars into energy, carbon dioxide, and alcohol in the absence of oxygen

converting sugars into energy and water in the absence of oxygen

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What is the independent variable in this practical?

volume of sugar solution

temperature of the water bath

number of carbon dioxide bubbles produced in 1 minute

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What is added to the boiling tube to prevent air from entering the solution?

oil

yeast

water

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How is the number of carbon dioxide bubbles produced in 1 minute measured?

by counting the bubbles

by weighing the bubbles

by measuring the volume of the bubbles

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What is the purpose of the water bath in this practical?

to heat the solution

to cool the solution

to maintain a constant temperature

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