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IB Cellular Respiration Demonstration Activity

Everyday you and all other organisms consume some sort of energy.  Glucose is often the form of energy consumed.  Plants, and some bacteria, are able to produce their own energy (glucose).  Humans, and most other organisms, unfortunately are not and thus we must obtain energy from some other means.  Once consumed, this energy must be converted into forms usable by cells.  This, in a nutshell, is the process of cellular respiration and the process we will examine further today.

Respiration in Yeast

Yeast is a simple organism that is often used in biological experiments; more commonly, it is used by bakers to ensure bread rises.  Yeast needs energy (glucose) just like any other organism and uses this energy to create energy usable by the organism.  This process can be observe by the byproducts of this reaction.



  1. Put 1 tablespoon full of yeast and 2 tablespoons full of sugar into the soda bottle.
  2. Fill the bottle, approximately 3/4 full, with warm water.
  3. Quickly stretch the balloon over the opening of the bottle.
  4. Seal the balloon on the bottle with masking tape.
  5. Gently swirl the bottle to speed up the reaction.
  6. Measure the diameter of the balloon every two minutes by using a piece of string (then measure the string’s distance with a ruler)
  7. Take measurements for a total of 10 minutes.


  1. What occurs when the yeast, sugar, and water is added to the bottle?

  1. What is the relationship between time and balloon size?

  1. Define Cellular Respiration:

  1. What is the first “step” in cellular respiration and state the results of this process

  1. What occurs, at a molecular level, when the sugar and water is added to the yeast?