Exploring Cellular Respiration with Yeast

Background: To obtain energy plants and animals must break down starches and carbohydrates into simple sugars. The most common simple sugar used in cellular respiration is glucose. This process occurs in the mitochondria of cells and is assisted by enzymes. The chemical equation for this is:

C6H12O6 + 6O2 Þ 6CO2 + 6H2O

Investigative Question: How does the concentration of sugar - high or low (10 g/50 mL water or 5 g/50 mL water) affect the rate of cellular respiration for yeast?

Hypothesis:

If…

Then…

Because…

Materials:


Procedure:

1.  One partner places 5.0g of sugar in one Erhlenmeyer Flask and the other partner places 10.0g of sugar in a second flask. Add 50.0mL of water (~27°C) to each. Swirl the Erlenmeyer Flasks in a circular motion to dissolve the sugar.

2.  Insert the S-shaped airlock into the top (the end with the larger diameter) of the Single Hole Bored Rubber Cork. Use a squirt bottle to fill the airlock with enough water so that it is half-way filled.

  1. Carefully remove the airlock from the flask. Add 1.5 g of baker's yeast to the sugar solution in each flask and cover the flasks with the rubber cork and s-shaped airlock apparatus. Swirl the solution to mix. Take temperature with thermometer until it registers at least ~27°C.
  1. After 15 minutes, start counting the number of bubbles that are released through the airlock.
  1. Count and record the number of bubbles that are released during the next 5.0 minutes.
  1. Repeat step 5 a total of three times. Record data in data table.

Data Table. After reading procedure, please create a data table to record bubbles counted in the 10 grams of sugar flask and in the 5 grams of sugar flask. Don’t forget you will need to record bubbles for first 5 minutes, second 5 minutes, third 5 minutes, and an average for each flask.

Questions:

1. Using the chemical equation provided at the beginning of this activity sheet and data from the data table, explain how you know cellular respiration is occurring. Hint – consider which gas is inside the bubbles.

2. Which organelle inside of human cells would normally break down sugar and produce energy?

3. Explain why understanding the process of cellular respiration is important to biology and life on earth. In your explanation provide details utilizing the chemical equation provided on the first page of this activity sheet.

4. How is respiration with your lungs related to cellular respiration? Explain!

5. What can you conclude based on the data? How does the concentration of sugar affect the rate of cellular respiration for yeast?

INCLUDE DATA FROM YOUR DATA TABLE! Was your hypothesis supported or not?

6. What aspects of the lab may have introduced inconsistencies? Consider the temperature of the water, whether the sugar was fully dissolved, accuracy in bubble counting, flaws in the design, etc.

7. What is your next question, otherwise known as the further investigative question?