Background Information:
Living things need to obtain energy in order to sustain their presence by performing their vital activities. For most of the vital activities energy is a must have concept. Cellular respiration is an example fort he process of obtaining energy in the form of ATP (Adenosine Triphosphate)There are two main processes to obtain energy by respiration. They are classified as Aerobic and Anaerobic respiration which are distincted by the use of oxygen.
Anaerobic respiration also stated as fermentation is the process to obtain ATP without the use of Oxygen. The process where yeast converts sugar into ethyl alcohol and carbondioxide is called ethyl alcohol fermentation. This is a result of the absence of oxygen for yeast to convert the organic substance (sugar) into cellular energy. This is considered an anaerobic process.
Yeast, as a member of the fungi family is neither an animal nor a plant,it is an eukaryotic micro organism. In ethyl alcohol fermentation sugar fungi form of yeast is used. The conversion of sugar into carbon dioxide and alcohol provides energy for the yeast cells. Glucose, sucrose, lactose and fructose are the sugars that are often used to perform experiments and observe the process of fermentation.
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Glucose is a type of sugar and a subcategory of the monosaccharides. It’s molecular formula is C6H12O6 . Sucrose is a subcategory of disaccharides as a combination of glucose and fructose. It’s molecular formula is C12H22O11. Lactose is another disaccharide derived from glucose and galactose with molecular formula C12H22O11 which makes it an isomer of sucrose. Fructose is a monosaccharide that is also known as fruit sugar and mostly bonds with glucose to form sucrose. It’s molecular formula is also C6H12O6.
The overall process of ethyl alcohol fermentation is the conversion of sugar into CO2 and alcohol (CH3CH2OH). The reaction is shown for glucose is as shown below ;
The simplicity of the chemical reaction is not preserved in reality and the products are far more complex that it is shown in the reaction. Sugar is also incorporated into other unmentioned products such as yeast biomass,acids and glycerol. This fermentation which was done using glucose as sugar was an example for the fermentation of a monosaccharide. Even though the process does dffer slightly,the amount of the released carbon dioxide and alcohol does change through monosaccharides and disaccharides.
The first step of alcoholic fermentation is the cleavage of glycosidic bonds between glucose and fructose by the enzyme invertase. Then glucose molecules are broken down into two pyruvate molecules by glycolysis. Thus as shown in the reaction above,glycolysis causes the reduction of NAD+ to NADH,ADP is converted into ATP and water molecules via substrate-level phosphorylation.
In the background researches of the previous experiments, it was estimated that different sugars would release different amounts of CO2. Glucose was expected to produce more carbon dioxide than other types of sugar because of it’s 6-Carbon structure. Sucrose was expected to be the runner up producer of carbon dioxide after Glucose because of it’s formation by the combination of glucose and fructose. It has also been considered that the attachment of a 5-Carbon sugar to a 6-Carbon sugar would limit the production of CO2. Fructose was not considered to have a major importance in the experiment but it was estimated that it would evolve some carbon dioxide. The smallest expectation was made on lactose because of it’s complex structure and the absence of enzymes that can break down galactose.
As the results, it was seen that in adequate amount of time both glucose and sucrose reached the maximum amount of CO2 release however sucrose reached it faster. Fructose produced a small amount of CO2 where lactose produced almost none.
Therefore it was stated that the structural differences between different types of sugar effects the CO2 release rate during the fermentation process of yeast.
Aim: To investigate the different fermentation rates of different sugars by measuring the CO2 release.
Research Question: How does the structure of sugar affect the rate of fermentation?
Variables:
Independent Variable
Type of sugar
Glucose,Fructose and Lactose were used.
Dependent Variable
Rate of ethyl alcohol fermentation
It depended on the structure of the sugar used.
Controlled Variable
Temperature
It was done in room temperature (38-40 ºC).
Amount of sugar
The amount of sugar was kept constant at 5 mg.
(Table 1)
Hypothesis:
If the structural complexity of the sugar increases,the rate of ethyl alcohol fermentation increases.
Material & Method
1. Materials
100 ml pure water (x4)
5 mg yeast (x4)
5 mg Fructose
5 mg Lactose
5 mg Glucose
100 ml beakers (x4, %5)
500 ml beaker
Tube (x4)
Syrnge (x4)
Vernier competer inference
Logger pro
Vernier CO2 Gas sensor
250 mL respiration chamber
Thermometer
Heater
Beral pipettes
2. Method
I. 5 mg of Fructose, Glucose and Lactose was measured separately.
II. Measured sugars were put into separated beakers.
III. 500 ml ofpure water was heated until it reached 38-40ºC and kept constant.
IV. 5 mg of yeast was put into tubes.
V. 25 ml of pure water was put into tubes which were filled with yeast (x4)
VI. Filled tubes were put into the pre-heated 500 ml beaker for 10 minutes.
VII. 2 ml of yeast solution was measured each tube using the syringes.
VIII. All of the solutions were added in to the chamber separately and CO2 sensor was put on the chamber.
IX. Amount of C02 release was calculated for each beaker.
X. All steps were repeated for 5 trials.
3. Design
Data Table (Raw Data):
Fructose
Time
Carbon Diocide Release
Trial 1
Trial 2
Trial 3
Trial 4
Trial 5
Mean Average
0 s.
0
0
0
0
0
0
20 s.
0
0
0
0
0
0
40 s.
821
830
825
820
820
823. 2
60 s.
877
883
873
875
879
877. 4
80 s.
921
918
920
925
922
921. 2
100 s.
959
957
960
962
958
959. 2
120 s.
981
985
980
982
980
981. 6
140 s.
994
999
993
992
995
994. 6
160 s.
1006
1004
1003
1007
1000
1004
180 s.
1009
1011
1007
1005
1010
1008. 4
200 s.
1016
1019
1014
1017
1015
1016. 2
220 s.
1018
1023
1020
1017
1019
1019. 4
240 s.
1022
1025
1027
1025
1020
1023. 8
(Table 2)
Glucose
Time
Carbon Dioxide Release
Trial 1
Trial 2
Trial 3
Trial 4
Trial 5
Mean Average
0 s.
0
0
0
0
0
0
20 s.
0
0
0
0
0
0
40 s.
1873
1870
1876
1875
1871
1873
60 s.
2113
2110
2114
2012
2015
2072. 8
80 s.
2313
2315
2310
2311
2314
2312. 6
100 s.
2443
2440
2445
2442
2443
2442. 6
120 s.
2563
2560
2566
2562
2564
2563
140 s.
2651
2652
2556
2550
2555
2592. 8
160 s.
2745
2744
2746
2743
2748
2745. 2
180 s.
2800
2800
2802
2805
2801
2801. 6
200 s.
2839
2840
2842
2835
2841
2839. 4
220 s.
2870
2872
2868
2873
2869
2870. 4
240 s.
2893
2895
2891
2890
2896
2893
(Table 3)
Lactose
Time
Carbon Dioxide Release
Trial 1
Trial 2
Trial 3
Trial 4
Trial 5
Mean Average
0 s.
0
0
0
0
0
0
20 s.
0
0
0
0
0
0
40 s.
679
680
677
681
680
679. 4
60 s.
744
745
743
748
745
745
80 s.
804
805
803
800
808
804
100 s.
851
855
848
850
852
851. 2
120 s.
895
900
897
890
892
894. 8
140 s.
922
925
917
930
920
922. 8
160 s.
943
940
945
946
941
943
180 s.
961
960
956
967
959
960. 6
200 s.
976
980
970
966
981
974. 6
220 s.
983
985
980
988
979
983
240 s.
994
990
992
995
989
992
(Table 4)
Water
Time
Carbon Dioxide Release
Trial 1
Trial 2
Trial 3
Trial 4
Trial 5
Mean Average
0 s.
0
0
0
0
0
0
20 s.
0
0
0
0
0
0
40 s.
757
756
758
750
760
756. 2
60 s.
876
877
880
873
875
876. 2
80 s.
970
973
967
977
963
970
100 s.
1022
1024
1020
1027
1017
1022
120 s.
1054
1055
1060
1052
1057
1055. 6
140 s.
1082
1080
1095
1079
1083
1083. 8
160 s.
1109
1109
1111
1107
1109
1109
180 s.
1124
1127
1120
1131
1125
1125. 4
200 s.
1131
1134
1131
1130
1137
1132. 6
220 s.
1143
1140
1145
1147
1141
1143. 2
240 s.
1154
1155
1150
1156
1155
1154
(Table 5)
Average Table (Processing Data):
Fructose
Time
CO2 Release
0
0
20
0
40
823. 2
60
877. 4
80
921. 2
100
959. 2
120
981. 6
140
994. 6
160
1004
180
1008. 4
200
1016. 2
220
1019. 4
240
1023. 8
Glucose
Time
CO2 Release
0
0
20
0
40
1873
60
2072. 8
80
2312. 6
100
2442. 6
120
2563
140
2592. 8
160
2745. 2
180
2801. 6
200
2839. 4
220
2870. 4
240
2893
Lactose
Time
CO2 Release
0
0
20
0
40
679. 4
60
745
80
804
100
851. 2
120
894. 8
140
922. 8
160
943
180
960. 6
200
974. 6
220
983
240
992
Water
Time
CO2 Release
0
0
20
0
40
756. 2
60
876. 2
80
970
100
1022
120
1055. 6
140
1083. 8
160
1109
180
1125. 4
200
1132. 6
220
1143. 2
240
1154
Calculation: The calculations for calculating the fermentation rate should be done using the formula (Final CO2 release-Initial CO2 release)(ppm)/Time(min). The calculations for the experiment is as following,
Fructose: (1023. 8-0)/4= 255,95
Glucose: (2893-0)/4=723,25
Lactose: (992-0)/4=248
Water: (1154-0)/4=288,5
Graphs
(Graph 1) Shows that the Final CO2 release of yeast with Fructose is 1023.
(Graph 2) Shows that the Final CO2 release of yeast with Glucose is 2893.
(Graph 3) Shows that the Final CO2 release of yeast with Lactose is 992.
(Graph 4) Shows that the Final CO2 release of yeast with water is 1154.
Conclusion and Evaluation
Conclusion
As it has been seen in the light of the datas taken during the experiment our hypothesis has been proven to be wrong. Because even though Glucose was a monosaccharide it’s fermentation rate has been measured higher than the Fructose who is a disaccharide. The complex structure of Frutose didn’t cause the fermentation rate to be higher. Thus the hypothesis haven’t been proven to be correct.
The information in the background information has led us to assume that the rate of the more complex sugar would be higher because the number of bonds was higher. But the principle monosaccharide Glucose had the highest fermentation rate n 4 minutes followed by the disaacharide Fructose.
The slowest fermentation rate was measured from the solution which consisted of only yeast and pure water. It was already estimated because Ethyl Alcohol Fermentation is focused on producing energy for yeast. But in the lacking of an energy providing substance such as sugar,enery can not be produced.
Thus,we can conclude our experiment by stating that the structural complexity of sugars affect the rate of ethyl alcohol fermentation however it is not the only factor that affects the rate when different types of sugars are used. The type of bonds is also an effective factor on the rate of ethyl alcohol fermentation.
Limitations:
Limitations
Sütun1
Deficiency on Temperature
While heating the 500ml beaker to 38ºC,it was a struggle to try to keep the
temperature around 39ºC and it may have affected the rate of
fermentation bacause it may have affected the solublity of the sugars in yeast solution.
Cleaning the Chamber
Cleaning of the chamber in switching between trials and
different sugars has also been a struggle because it couldn’t be
cleaned totally. Hence this may have affected the fermentation
rate because of the mixture of sugars.
Minimum value of syringe
The operation done by the syringe was a little value
but the it’s minimum value was hard to read.
Improvement
The lack of controlling during the heating of the 500 mL beaker caused a uncertainty of the datas of the experiment. We could have used a more precise heater and quickly used it in the solutions. The largest uncertainties were caused by person-based uncertanities. For example if more time was spent or some tools were used in cleaning the respiration chamber the datas of the experiment could have been more accurate. . One of the other limitations during the experiment was that the use of the syringe was hard because of it’s form.
If the stated limitations were decreased to minimum,the datas could have been more precise and accurate.
References
BiologyMad A-Level Biology. 02 Mar. 2009
Cohn, Don. (1999) Science in the Real World, Microbes in Action; How Long Will I Be Blue? Universityof Missouri
Brazillian archives of biology technology. vol. 51 no. 3 Curitiba May/June 2008
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