Cell Respiration Lab Report

TITLE: The Effect of Temperature on Cell Respiration in Yeast

ABSTRACT: In this lab, our goal was to find out whether or not temperature affects the rate of cell respiration. We used yeast as our organism, adding it, along with the glucose that it needs for cell respiration to occur, to four different vials. Each of these four vials had a syringe connected to it by a tube, allowing for us to see the volume of carbon dioxide produced by the cell respiration. After each of these vials were exposed to a different temperature, we found that the rate of cell respiration initially increased along with the increase in temperature, but as the temperature was increased past a certain point, or plateau, the rate of respiration then decreased.

INTRODUCTION: Cell respiration is a process that occurs in our cells, and involves converting glucose, which we get from the food we eat, into ATP energy. The chemical equation that represents cell respiration is C₆H₁₂O₆ + 6 O₂ à  6 H₂O + 6 CO₂ + 36-38 ATP. The Glucose is converted into ATP through 3 different processes, which are Glycolysis, the Krebs Cycle, and the Electron Transport System. Two products that are created through this reaction, other than ATP, are H2O and CO2. It is this produced CO2 that we will measure in our experiment to determine the rates of respiration. Since the volume of produced CO2 represents the rate of respiration, then temperatures affect on amount of CO2 produced directly represents its effect on the rate of respiration.

HYPOTHESIS: If equal amounts of yeast are added to a four different vials of water that each contain glucose, and are then exposed to four different temperatures, then the yeast exposed to a lower temperature than the control, which is the yeast at room temperature, will a lower rate of respiration than the control, and the yeast exposed to temperatures greater than the control will have higher rates of respiration than the control, because a decrease in temperature would result in less molecular motion, and less reaction, whereas an increase in temperature would result in an increase in molecular motion, and therefore an increase in rate of reaction, or rate of respiration.

MATERIALS:

1. 140 mL Water

2. 4.0 g Yeast

3. 4.0 g Glucose

4. 0.8 g Salt

5. Four Vials

6. Four Syringes

7. Four Connecting Tubes

8. Four Stoppers with Open Vent

9. Mass Scale

10. Heating Pad

11. Heater

12. Ice Bath

13. Graduated Cylinder

14. Beaker

15. Stop Watch

PROCEDURE:

1. Measure 35 mL of water and pour into four vials.

2. Measure and add 1.0 g glucose into each vial.

3. Measure and add 0.2 g salt to each vial.

4. Measure 1.0 g yeast for each vial.

5. Attach the four connecting tubes to the four syringes on one side, and to the stoppers with open vents on the other side. 

6. Push down the syringe to start at 1.0 mL. Then place the stoppers on each vial.

7. Put the vials into their temperature locations. One sits at room temperature, one is placed in an ice bath, one sits in a heater, and one sits in a beaker of water on a heating pad.

8. Pour the measured yeast into each vial, put the stoppers on, and start a timer.

9. Record the new mL shown on the syringes every 2 minutes. This represents the CO2 that is produced.

10. Make a data sheet and a graph.

RESULTS:

CO2 Produced + 1.0 mL
Minutes	Cold	RT	80*C	48*C
0	1.0 mL	1.0 mL	1.0 mL	1.0 mL
2	1.0 mL	1.0 mL	1.0 mL	1.0 mL
4	1.3 mL	1.2 mL	1.4 mL	1.0 mL
6	1.3 mL	1.1 mL	1.4 mL	0.8 mL
8	1.2 mL	1.7 mL	2.2 mL	2.6 mL
10	1.0 mL	2.0 mL	3.0 mL	5.0 mL
12	1.0 mL	2.2 mL	3.5 mL	8.0 mL
14	1.0 mL	2.3 mL	3.6 mL	10.0 mL

CONCLUSION: Our results from this experiment show that yeast held at temperatures below our control, which is room temperature, yield lower amounts of CO2 and therefore produce lower rates of cell respiration. On the other hand, yeast held at higher temperatures than the control yeast, once again the yeast at room temperature, yield larger amounts of CO2 and higher rates of cell respiration, but only up to a certain level. Since the yeast in the hottest temperature vial produced less CO2 than the yeast in the second hottest vial, this seems to suggest that their is a optimal temperature, and that after that temperature is exceeded, the rate of respiration will begin to decrease. Once the temperature passes the plateau, or temperature range that yields the highest possible rate of respiration, the enzymes that are used in the mitochondria are likely deformed and become no longer able to do their job. When one of these enzymes, for example ATP Synthase, become deformed, the substrates can no longer fit into the active sit and cannot be changed into products, such as ATP, water, and CO2. Our findings in this experiment somewhat reject my hypothesis. While I was correct in my prediction that lower temperatures than the control would yield lower rates of respiration, and higher temperatures than the control would produce higher rates of respiration, I did not predict that their would be high enough temperatures at which the enzymes would become deformed and cause a lower rate of respiration. Two constants in this experiment were the sugar that we added, glucose in all four, and the amount of the sugar added to each vial, which was 1.0 g for each. A potential sources of error for this experiment is that we don't think we added salt to one of the vials, and instead added double to one of them. Another potential source of error is that some CO2 may have escaped when one of the stoppers seemed loose.



CITATION:

Quick, Kevin, Holly Kiamanesh, Rosie Montague, Jennifer Blanchette, and Barbara

Akre. The Webb Schools Honors Biology Textbook. Claremont: CK-12

                Foundation, 2012. eBook.