Respiration Lab: Who Made All That Gas?
Your name:
The cells of all living organisms require a constant supply of energy to carry out the many functions necessary for life. The molecule used to provide energy is ATP (adenosine tri- phosphate). The major source of ATP for all cells is the oxidation of glucose, via the process of cell respiration. The initial steps of cell respiration, called glycolysis, occur in the cells of all organisms (with a few bacterial exceptions).
For most organisms, the process of cell respiration is an oxygen-consuming process. Following glycolysis, a process that occurs in the cytoplasm, in which glucose is converted to pyruvic acid, the Krebs cycle and electron transport chain occur in the mitochondria. CO2 is given off during the Krebs cycle and the hydrogen electrons removed from the pyruvic acid backbone are transferred to the electron carriers NADH and FADH2. These electrons are then passed through the electron transport chain to power the movement of hydrogen ions against a concentration gradient. Without oxygen, which functions as the final electron acceptor in the electron transport chain, the process of aerobic respiration cannot happen. For each glucose molecule oxidized, 36 - 38 ATP are produced. Most organisms cannot survive without aerobic respiration.
Purpose: In this lab activity we will see how a microscopic organism (yeast) can use the energy found in sugar. One of the problems you must solve is to decide how we know a living thing is using the energy.
How do you know you are using the energy from the food you eat (what evidence do you have that we use this energy)? (1 point)
What is the chemical formula for cellular respiration? (1 point)
What is the purpose of cellular respiration? (1 point)
Predictions: Make these informal predictions before you continue writing up the lab. (4 points)
What do you think will happen to the bottle and balloon that has sugar but no yeast? Will it produce a lot of gas? A medium amount? A small amount? No gas?
What do you think will happen to the bottle and balloon that has yeast with no flour or sugar? Will it produce a lot of gas? A medium amount? A small amount? No gas?
______
What do you think will happen to the bottle and balloon that has yeast and sugar only? Will it produce a lot of gas? A medium amount? A small amount? No gas?
______
What do you think will happen to the bottle and balloon that has yeast and flour only? Will it produce a lot of gas? A medium amount? A small amount? No gas?
Procedure: Your teacher will explain this. Follow the recipe on your group’s recipe card.
Data Table: (4 points)
Flask # and Contents / Balloon circumference (cm)1 No yeast
2 Yeast only
3 Yeast plus sugar
4 Yeast plus flour (starch)
Analysis Questions: (answer on a separate piece of paper)
1. What are the 3 stages of cellular respiration? (1 point)
2. Where do each of the stages of cellular respiration take place? (1 point)
3. What is required for each stage of cellular respiration (include each stage and state what is required)? (1 point)
4. What is produced during each stage of cellular respiration (include each stage and what is produced)? (1 point)
5. What energy transformations take place in cellular respiration? (1 point)
6. What are the inputs/reactants for cellular respiration? (1 point)
7. What are the outputs/products of cellular respiration? (1 point)
8. Explain the relationship between photosynthesis and cellular respiration. (1 point)
Use the data table to answer questions 7-11. Answer in complete sentences for full credit.
9. Why was no gas produced in Flask 1? (1 point)
10. Why was no gas produced in Flask 2? (1 point)
11. Explain why was there more gas produced in Flash 3 than Flask 4 even though both sugar and starch contain energy. (1 point)
12. Compare your 4 predictions to what actually happened (how did the final results compare to each of your predictions)? (4 points)
13. Do you think changing the amount of water in the flask would have affected the amount of gas produced by the yeast? Explain. (1 point)