Yeast Respiration Lab Report

The Effect of Temperature on the Rate of Yeast Respiration

Abstract
Carbon dioxide is a waste product of yeast respiration. A series of experiment was conducted to answer the question; does temperature have an effect on yeast respiration? If the amount of carbon dioxide is directly related to temperature, then varying degrees of temperature will result in different rates of respiration in yeast. The experiment will be tested using yeast and sugar at different water temperatures. I predict the warm temperature will be optimal for yeast respiration therefore the most carbon dioxide will be released. The experiments tested yeast respiration in both, warm water at 42 degrees Celsius and at room temperature. The outcome of the experiment indicates the warm water is optimal for yeast respiration in comparison to cold water.

Introduction Respiration is the process that converts sugar known as glucose to energy, in this case ATP (Adenosine Triphosphate). This process is found in all living organisms. Respiration can occur in two ways, aerobic and anaerobic. Aerobic respiration requires oxygen to produce energy. Anaerobic respiration does not require oxygen to produce energy. In yeast respiration the yeast cells are capable of respiration in the absence of oxygen (Kelly, et. al, 2001). Yeast has the ability to breakdown sugar into glucose, which causes the release of carbon dioxide. Carbon dioxide is a waste product of yeast respiration. Yeast is a living organism therefore optimal temperature is needed for activation of energy production. The cellular respiration rate in yeast can be affected by temperature. Temperature can alter the amount of oxygen needed for respiration and the amount of energy used. If a high temperature is present, the yeast will die and no cellular respiration will take place. Does temperature have an effect on yeast respiration? If the amount of carbon dioxide is directly related to temperature, then varying degrees of temperature will result in different rates of respiration in yeast. The experiment will be tested using yeast and sugar at different water temperatures. I predict the warm temperature will be optimal for yeast respiration therefore the most carbon dioxide will be released. The cold temperature will have the least yeast respiration, which will affect the amount of carbon dioxide produced. Further experiments using different dependent variable were also be used to test temperatures effect. The different dependent variables will be agave syrup, molasses, and karo syrup mixed with yeast in independent solutions. I predict for these experiments the type of sugar used will determine the amount of carbon dioxide produced.
Methods
Two pipettes were sealed at the narrow ends using parafilm. Yeast and sugar were added to distilled water and mixed thoroughly to activate the yeast. Once activated, 10 mL of the yeast/sugar mixture were filled into the pipette using disposable Pasteur pipette. A test tube was placed over the open end of the pipette then inverted. The fluid level on the pipette was recorded. One tube was placed in a warm water bath at 42 degrees Celsius and the other was placed in a cold water bath at room temperature. The level of the liquid was recorded every five minutes until no more reading could be read. Four pipettes were sealed at the narrow ends using parafilm. Yeast and sugar were added to distilled water and mixed thoroughly to active the yeast. Another mixture was made with yeast and agave syrup. Once yeast was activated in both solutions, 10 mL of the mixture were filled into the pipette using disposable Pasteur pipette. Yeast/sugar mixture was transferred into two pipettes. A test tube was placed over the open end of the pipettes then inverted. The fluid level on the pipettes were recorded. Both tubes were placed in a warm water bath. Yeast/agave mixture was transferred into two pipettes. A test tube was placed over the open end of the pipettes then inverted. The fluid level on the pipettes were recorded. Both tubes were placed in a warm water bath. The level of the liquid was recorded every five minutes until no more reading could be read. Two pipettes were sealed at the narrow ends using parafilm. Yeast and molasses were added to distilled water and mixed thoroughly to activate the yeast. Once activated, 10 mL of the yeast/molasses mixture were filled into the pipette using disposable Pasteur pipette. A test tube was placed over the open end of the pipette then inverted. The fluid level on the pipette was recorded. One tube was placed in a warm water bath and the other was placed in a cold water bath. The level of the liquid was recorded every five minutes until no more reading could be read. Two pipettes were sealed at the narrow ends using parafilm. Yeast and sugar were added to distilled water and mixed thoroughly to active the yeast. Another mixture was made with yeast and karo syrup. Once yeast was activated in both solutions, 10 mL of the mixture were filled into the pipette using disposable Pasteur pipette. Yeast/sugar mixture was transferred into the pipette. A test tube was placed over the open end of the pipette then inverted. The fluid level on the pipette was recorded. The tube was placed in a warm water bath. Yeast/karo syrup mixture was transferred into the pipettes. A test tube was placed over the open end of the pipette then inverted. The fluid level on the pipette was recorded. The tube was also placed in a warm water bath. The level of the liquid was recorded approximately even three to four minutes until no more reading could be read.
Results
The results indicate at the start of the experiment the reading was consistent for all three attempts using yeast and sugar placed in warm and cold water. In two experiments the tubes placed in the warm water bath both produced more carbon dioxide faster than the tube in cold water, whereas in the third experiment there was no change then a sudden change in both tubes. See Table 1.0 -1.2 for results.
Table 1.0 Comparison between temperatures effect on yeast respiration.
Time (Minutes)
Total Volume of Carbon Dioxide Produced (mL)

Cold Water
Warm Water
Start
5.5
5
5
5.5
5
10
4.5
0
15
4
n/a
20
2 n/a 25
0
n/a
30
n/a n/a Table 1.1 Comparison between temperatures effect on yeast respiration.
Time (Minutes)
Total Volume of Carbon Dioxide Produced (mL)

Cold Water
Warm Water
Start
5.5
5.5
5
5.2
5.1
10
4.8
1.8
15
4.5
0
20
4.1 n/a 25
4.0
n/a
30
3.9 n/a Table 1.2 Comparison between temperatures effect on yeast respiration.
Time (Minutes)
Total Volume of Carbon Dioxide Produced (mL)

Cold Water
Warm Water
Start
5
5
5
5
5
10
n/a n/a 15 n/a n/a
20
n/a n/a 25 n/a n/a
30
n/a n/a In the experiment comparing yeast/sugar mixture and yeast/agave syrup mixture both mixtures produced carbon dioxide at fairly consistent rates until the last ten minutes. The yeast/agave mixture produced carbon dioxide faster in one tube compared to the other. Similarly this was the same result for the yeast and sugar in warm water used in comparison. See Table 1.3 for results.
Table 1.3 Comparison between temperatures effect on yeast respiration using Yeast/Sugar and Yeast/Agave syrup.
Time (Minutes)
Total Volume of Carbon Dioxide Produced (mL)

Yeast and Sugar Mixture
Yeast and Agave Mixture

Warm Water
Warm Water
Warm Water
Warm Water
Start
5
5
5
5
5
4.2
4.1
4.5
4
10
2
2
3
0.5
15
0
0.5
0
n/a
20
n/a
0
n/a n/a 25 n/a n/a n/a n/a
30
n/a n/a n/a n/a In the experiment comparing yeast/molasses mixture in warm and cold water, the tube in warm produced carbon dioxide faster, which is a similar result to the original experiment. See Table 1.4 for results.
Table 1.4 Comparison between temperatures effect on yeast respiration using Yeast/Molasses mixture.
Time (Minutes)
Total Volume of Carbon Dioxide Produced (mL)

Cold Water
Warm Water
Start
5
8
5
4.8
6.4
10
4.4
3.7
15
3.5
1.5
20
3 n/a 25
2.3
n/a
30
1.3 n/a In the experiment with the yeast/sugar mixture and yeast/karo syrup mixture both placed in warm water, the tube with yeast/sugar produced carbon dioxide at a faster rate compared to the yeast/karo syrup mixture. See Table 1.5 for results
Table 1.5 Comparison between Yeast/Sugar and Yeast/Karo syrup in the same water temperature.
Time (Minutes)
Total Volume of Carbon Dioxide Produced (mL)

Yeast and Sugar Mixture
Yeast and Karo Mixture

Warm Water
Warm Water
Start
5
5.3
3
3.9
5.3
7
2.5
5
9
0.3
4
11
n/a
3.6
13 n/a 2.4
15
n/a
0.5
16 n/a n/a

Discussion Yeast will undergo cellular respiration by way of anaerobic respiration when supplied with sugar. As we know, anaerobic respiration uses available sugars to produce energy with carbon dioxide as a waste by product. Temperature is a factor on cellular respiration in yeast because as the temperature increases it reaches an optimal temperature to produced the most energy and waste. Similarly cold temperatures and hot temperatures will not have the same effect. The results of the experiment proved the hypothesis to be correct. The experiments conducted proved cellular respiration in yeast, produced carbon dioxide at a faster rate when done at a warm temperature, therefore optimal temperature is required for the most productivity.
Limitations I found in these experiments could be the amount of yeast used can have an effect on the amount of respiration that will occur. Yeast that is considered old could also play a factor in the amount of respiration that will occur to produce energy. Mixing the yeast solutions for a longer period of time could also affect the outcome of the experiment. The experiment could also be done using a smaller range of different temperatures for more accuracy on finding an optimal temperature to view the effects of temperature on yeast respiration. A similar experiment was conducted to test the effect of increased temperature on baker’s yeast in dough. The results in the experiment coincided with the results of the yeast respiration lab. The bakers yeast in dough placed at 37 degrees Celsius produced carbon dioxide faster and helped the dough rise compared to yeast in dough placed at 28 degrees Celsius (Aboaba & Obakpolor, 2010). In conclusion temperature has an effect on yeast respiration, however an optimal temperature is required.

Reference
Aboaba, O., & Obakpolor, E. (2010). The leavening ability of baker’s yeast on dough prepared with composite flour (wheat/cassava). African Journal of Food Science Vol., 4(6), 325-329. Retrieved from http://www.academicjournals.org/ajfs/pdf/pdf2010/Jun/Aboaba and Obakpolor.pdf
Kelly DJ, Hughes NJ, Poole RK. Microaerobic Physiology: Aerobic Respiration, Anaerobic Respiration, and Carbon Dioxide Metabolism. In: Mobley HLT, Mendz GL, Hazell SL, editors. Helicobacter pylori: Physiology and Genetics. Washington (DC): ASM Press; 2001. Chapter 10. Available from: http://www.ncbi.nlm.nih.gov/books/NBK2411/