Yeast and Cellular Respiration

Background:

Yeasts are unicellular microorganisms of the fungi kingdom. They are facultative anaerobe, which means that they can respire or ferment depending upon environmental conditions. In the presence of oxygen, respiration takes place (aerobic respiration). Without oxygen present, fermentation occurs (anaerobic respiration). Both processes require sugar to produce cellular energy. The chemical reaction of fermentation produces ethanol and carbon dioxide as metabolic waste products instead of water, as seen in regular cellular respiration.

Objective:

Step 1:

In this lab, students will use the respiration powers of yeast to blow balloons. This activity will reinforce the basic principles of respiration as a fundamental metabolic process for living organisms using yeast as a model. It will also explore how humans use this biological knowledge in everyday life.

Step 2:

You will look at Neto’s Demo and adjust independent and dependent variables in the lab to test your own hypothesis and how cellular respiration works optimally.

1. Question:

1.  Purpose: A single question that states the problem you are trying to answer.

3. Hypothesis: If…[insert what is changed or what you are doing], then [insert what you think will happen/what you think you will see or observe], because [insert WHY you think this will happen, give a reason for your guess].

Materials: This is a list of all the materials that you need to do the experiment.  This list should include the NUMBERS of the items needed.

THIS IS A STARTING POINT, YOU WILL NEED TO ADD AND SUBTRACT MATERIALS DEPENDING ON YOUR SPECIFIC LAB.

  • balloons  
  • Test tube
  • 1 teaspoon (5mL) active dry yeast  
  • sugar or other reactant  
  • Graduated cylinder  
  • water (temperature of your choice
  • ruler

Procedure: List the specific steps that you went through to conduct the experiment.

THIS IS A STARTING POINT, YOU WILL NEED TO ADD AND SUBTRACT STEPS DEPENDING ON YOUR SPECIFIC LAB.

Safety:  Remind students there is NO eating or drinking in the lab.  Students must not attempt to inflate the balloons with their mouths, especially after it is filled with the reacting agents.

Procedure:

1. Place test tube(s) in rack and label your test tube with your names and number. One the whiteboards, be clear about what number has was independent variable.

2. Have a carefully supervised student pour the yeast and the sugar (or other reactant) into the test tube.

3. Then fill the test tube with water halfway. BE CAREFUL WITH HOT WATER!

3. Place balloon tightly over test tube

4. Place the balloon in a well supervised area and wait. Set a timer to measure the diameter of the balloon at 5 minutes, 10 minute and 20 minutes.

5. Chart results.

Identify the Independent and Dependent Variable:

  • X:
  • Y:

Data Table:

  • Should be done with Google Sheets
  • Title
  • Heading for each column (what was being measured)
  • Units for each column

Conclusion: 

Paragraph One:

  • Claim – Your claim is the answer to the question you were trying to answer. This should be the first sentence in your paragraph. If you have multiple claims, you need to address them in separate paragraphs.
  • Evidence – Your evidence is the data you collected during the lab. Use your data to support and backup your claim. Discuss the patterns in your data; reference the ACTUAL numbers and trends in your data table and graph.
  • Reason – Provide an explanation for what your data tells you. Explain why or how the evidence/data supports your claim.

Paragraph Two: (Honor’s)

  • Claim – Your claim is the answer to the question you were trying to answer. This should be the first sentence in your paragraph. If you have multiple claims, you need to address them in separate paragraphs.
  • Evidence – Your evidence is the data you collected during the lab. Use your data to support and backup your claim. Discuss the patterns in your data; reference the ACTUAL numbers and trends in your data table and graph.
  • Reason – Provide an explanation for what your data tells you. Explain why or how the evidence/data supports your claim.