LABORATORY EXPERIMENT



Name:____________________

LABORATORY EXPERIMENT

Cellular Respiration by Yeast

Biology

A. Purpose:

Cellular respiration is the process that allows cells to convert glucose (sugar broken down from food sources) into energy. Aerobic cellular respiration takes place in the presence of oxygen and produces carbon dioxide and water as byproducts. In this experiment we will use yeast, unicellular eukaryotic organisms, to demonstrate cellular respiration. Consider the following chemical reaction:

[pic] + Energy (ATP)

[pic] + Energy (ATP)

B. Research the Problem

1. What are the products of the products of cellular respiration?

2. What form of matter (solid, liquid or gas) do you think each of these products are?

3. How can you tell if a chemical reaction is happening?

4. Explain a few (no less than 2) ways you can inflate a balloon?

5. What is yeast used for in our society?

C. Materials:

? Yeast mixture

? Glucose solution

? Erlenmeyer flasks, 500 ml

? Beaker, 1000 ml

? Graduated Cylinders (10ml, 100ml)

? 1 Balloon (round, 7-10 inch)

? 30 cm string and ruler

D. Procedures:

1. At each lab table, work in groups of three or four. Assign each lab partner different materials to get.

2. Fill 1000 ml BEAKER with 200 ml of water. Place on hotplate and turn on to LOW. This is your warm water bath for your experiment.

3. Measure a piece of string, yard or thread to the length of 30 cm, using a ruler. Take both, string and ruler, to the lab table to measure diameter of balloon.

4. Set up a clean 250 ml Erlenmeyer flask on lab table with:

- 100 ml of room temp water

- 2g of yeast (get from your teacher)

- Sugar (you will weigh the sugar but may put in as much or as little as you like. Be sure to record the amount that you choose to put in)

5. Add ingredients to the Erlenmeyer flask.

6. Gently swirl the mixture, and quickly place a balloon over the top of the flask, making sure flask is sealed.

7. Place flask (with attached balloon) in warm water bath prepared by your teacher.

8. Watch your experiment and record the diameter of the balloon in intervals of 5 minutes for the duration of about 45 minutes. Record the measurements in the table on the next page.

Data Table |Amount of Sugar _____________ g |Observations | | | | | | | | | | | | | |Diameter of balloon (cm) | | | | | | | | | | | | | |Time (min) |0 |5 |10 |15 |20 |25 |30 |35 |40 |45 | |

Questions:

1) Is yeast a living cell? How do you know? _________________________________________________ ___________________________________________________________________________________

2) What is the equation for cellular respiration? _______________________________________________ ___________________________________________________________________________________

3) Which organelle does cellular respiration occur in? __________________________________________ ___________________________________________________________________________________

4) What is the purpose of the balloon in this lab? What is it helping us measure? ____________________ ___________________________________________________________________________________ ___________________________________________________________________________________

5) Did your lab work as expected? Explain why or why not. _____________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

6) What could have been done to increase the rate of cellular respiration? Explain how: ____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

7) Which group had the most products? Why do you think they had the most? Explain.

_____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

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Graph Title: ____________________________________________________________

Diameter of Balloon (cm)

Time (minutes)

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