Download Internal Assessment: Fermentation Biology Higher Level

Internal Assessment: Fermentation
Biology Higher Level
Examination session: May 2012
“The Effect of Different Concentrations of Glucose in the Anaerobic Respiration by
Yeast”
I.- Introduction
The world glycolysis (sugar splitting) is thought to have been one of the first
biochemical pathways to evolve. It uses oxygen and occurs in the cytosol of the cell.
The sugar splitting proceeds efficiently in aerobic or anaerobic environments. Glycolysis
is the metabolic pathway that is common to all organisms on Earth. (Miller, & Levine,
2006) However, when oxygen is not present, the process of glycolysis is combined with
different pathways. When combining these pathways with glycolysis, fermentation takes
place.
“Some organisms derive their ATP completely without the use of oxygen without the use
of oxygen and are referred to as anaerobic. The breakdown of organic molecules for
ATP production in anaerobic way is also called fermentation.” (Damon, McGonegal, &
Ward, 2009) “During fermentation, cells convert NADH to NAD+ by passing high energy
electrons back to pyruvic acid. This action converts NADH back into the electron carrier
NAD+, allowing glycolysis to continue producing a steady supply of ATP.” (Miller, &
Levine, 2006)
There exist two types of fermentation which are alcoholic fermentation and lactic acid
fermentation. However, this practice is focus on alcoholic fermentation due to the
production of carbon dioxide (CO2) gas.
Alcoholic fermentation. Yeast (single-celled fungus) uses this type of fermentation in
order to produce ATP molecules. Yeast cells take in glucose from the environment and
generate a net of gain of two ATP by way of glycolysis. (Damon, McGonegal, & Ward,
2009) Glycolysis produces organic products known as pyruvate molecules. The next
step is taken when yeast converts both of the 3-carbon pyruvate molecules to produce
“The Effect of Different Concentrations of Glucose in the Anaerobic Respiration by Yeast
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molecules of ethanol. “Ethanol is a 2-carbon molecule, which means that a carbon atom
was lost during the conversion. Therefore, the carbon atom is given off in a carbon
dioxide molecule. The waste products produced by yeast (ethanol and carbon dioxide)
are spread into the environment.” ( D a m o n , M c G o n e g a l , & W a r d , 2 0 0 9 )
II.- Objective
The objective of this practice is to study the effect of different concentrations of glucose
on the rate of anaerobic respiration in yeast for the production of carbon dioxide gas
(CO2).
III.- Research Question
How will the effect of different concentrations of glucose (5%, 10%, 15%, 20%, 25%) be
on the production of carbon dioxide gas (CO2) by yeast fermentation at 37°C?
IV.- Hypothesis
If increasing the concentration of glucose then the rate of anaerobic respiration in yeast
will be faster. Therefore, the carbon dioxide (CO2) produced by the reaction will
increased at a higher concentration.
This will happen because for a great part of the reactions occurring in nature in our daily
life, increasing the concentration of one of the reactants increases the rate of the
reaction. For a reaction to occur, the particles of the reactants must collide. Therefore,
“at a higher concentration the collisions are greater.” (Clark, 2002) As yeast contains
certain types of enzymes, the effect of substrate concentration in enzymes is as follows:
“As the concentration of substrate increases, the rate of reaction will increase as well”
(Damon, McGonegal, & Ward, 2009). This is because there is an increase in collisions
between molecules so if there is a higher quantity of molecules, these will collide in a
greater rate. Increasing glucose concentration, there will be more molecules of glucose
to break down in order to produce more ethanol and CO2 gas. In breaking down
molecules, there are more heat energy released and, as a result more molecules will
collide with one another and with the enzymes in yeast. However, we cannot generalize
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the previous statement, because not in all the cases the following statement will have
the same effect. Enzymes have a certain rate at which they can work better.
V.- Variables
For anaerobic respiration in yeast, there is one main factor that affects directly the rate
of reaction between glucose and yeast: temperature. In order for the reaction to take
place, several factors must be met. This factor will be controlled as it can be appreciate
in the following table:
Table 1. Identification of Variables
Type of
Variable
Units
Control Method
variable
Independent
variable
Glucose
concentration
Percentage The percentage of glucose solution
(%)
was controlled at the moment of
making the solution. Five different
concentrations of glucose solution were
used (5%, 10%, 15%, 20%, and 25%)
Dependent
variable
Carbon dioxide
Milliliters
The amount of carbon dioxide gas
(CO2) gas
(ml)
produced was monitored using a 250
production
ml graduated cylinder (±5%). It was
measured by means of volume of water
displaced.
(Continuation) Table 1. Identification of Variables
Type of
Variable
Units
Control Method
Time
Minutes
Data will be collected at intervals of 5
variable
Controlled
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variables
(min)
min. during a period of 25 min. (5, 10,
15, 20 and 25 min) by means of a
chronometer (± 0.5 s.).
Temperature
Celsius
An optimum temperature of 37°C was
degrees
used to carry out the reaction. The
(°C)
temperature of the water bath was
monitored
by
means
of
a
thermometer (± 0.5 ˚C)
Yeast
Percentage
Concentration of yeast was controlled
concentration
(%)
at the moment of making the solution.
Yeast
was
used
at
a
10%
concentration.
Yeast volume
Milliliters
(ml)
50 ml of yeast solution were required
for
each
trial
throughout
the
experiment.
Glucose volume
Milliliters
In each trial 50 ml of glucose solution
(ml)
were used at five different concentrations
(5%, 10%, 15%, 20%, and 25%).
VI.- Materials:

250 ml Graduated cylinder (±5 %)

100 ml Graduated cylinder (±5 %)

125 ml Flask (±5 %)

500 ml Beaker (±10 %)

Thermometer (±0.5 °C)

Chronometer (± 0.5 s)

Rubber stopper

Water bath

Support stand rod (base, support and clamp/holder)

Container

Incubator
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
Test tube rack
Reagents

250 ml of 5% Glucose solution

250 ml of 10% Glucose solution

250 ml of 15% Glucose solution

250 ml of 20% Glucose solution

250 ml of 25% Glucose solution

1. 25 L of 10% Yeast solution

Tap water
VII.- Procedure
Focusing on glucose and yeast reaction, the following method was designed with the
objective to measure the production of carbon dioxide (CO 2) gas. It must be pointed that
the amount of CO2 was measured by means of the volume of water displaced in the 250
ml graduated cylinder (±5%). Five repetitions were carried out for each of the different
concentrations of glucose solution at intervals of 5 min (5, 10, 15, 20 and 25 min). The
following procedure was used for the development of the experiment:
1. Each flask and beaker used was labelled in order to avoid any confusion.
2. Then the 10% yeast solution was incubated at 37 °C inside the incubator, for a
period of one hour. In addition, each of the five glucose concentrations was
incubated for a period of one hour (at the same temperature), in order to fast the
experiment.
3. While yeast and glucose were being incubated; the electric water bath was filled
with 2 liters1 of tap water and it was turned on.
4. Then the temperature of the water bath was monitored by means of a
thermometer (±0.5 °C) until it reached an optimum temperature of 37 °C.
5. After setting the water bath, a container was filled with approximately 2 liters2 of
tap water.
1
2
The amount of water tap does affect neither the experiment nor the results.
The amount of water tap does affect neither the experiment nor the results.
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6. A support stand rod was set up besides the container with tap water in order to
hold the 250 ml graduated cylinder (±5%) by means of a clamp/holder attached to
the rod.
7. Before holding the 250 ml graduated cylinder (±5%) by means of the support
stand rod, the graduated cylinder was submerged inside the container in order to
fill the graduated cylinder with tap water.
8. Once the 250 ml graduated cylinder (±5%) was filled with tap water, it was placed
in the support stand.
9. The initial volume of the 250 ml graduated cylinder (±5%) was collected before
initiating the fermentation process.
10. Then the hose of the rod stopper was placed underneath the 250 ml graduated
cylinder (±5%).
11. Once the one hour period was completed, the yeast solution and each of the five
concentrations of glucose solution were taken out from the incubator.
12. Then 50 ml of 5% glucose solution were measured by means of the 100 ml
graduated cylinder (±5 %).
13. After that, the 50 ml of 5% glucose solution were placed into a 125 ml flask (±5
%) in order to introduce it into the electric water bath.
14. In addition, 50 ml of 10% yeast solution were measured by means of the 100 ml
graduated cylinder (±5 %).
15. Then the 50 ml 10% yeast solution were placed into another 125 ml flask (±5 %)
labelled in order to introduce it into the electric water bath together with the flask
containing the 50 ml of 5% glucose solution.
16. The temperature of both solutions was regulated by means of a thermometer
(±0.5 °C), until they reach the optimum temperature of 37 °C.
17. Once the temperature was reached, the reaction was carried out. The flask
containing the 5% glucose solution was mixed with the flask containing 10%
yeast solution.
18. The flask was closed as fast as possible using the rod stopper. This step was
taken into action as fast as possible to prevent a loss of CO2.
19. Then the chronometer (±0.5 s) was activated once the reaction had begun.
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20. In order to measure the volume of water displaced from the 250 ml graduated
cylinder (±5%) to determine the production of CO2 gas delivered by the reaction,
the stopwatch was stopped in intervals of 5 minutes during a 25 min period.
21. Then the water displaced from the graduated cylinder was recorded, by
measuring the final volume in milliliters.
22. The data was collected.
23. For each of the five trials of the same glucose concentration, the same procedure
was followed. After ending with one complete concentration, the same process
was repeated for each of the five glucose concentrations.
VIII.- Set-up of apparatus
Figure 1. Glucose and yeast reaction producing CO2
Figure 2. Temperature controlled by the thermometer
IX.- Safety
During the development of the experiment, neither dangerous materials nor hazard
reactants were used, so the need of gloves and safety goggles was not necessary. In
addition, it was not used a dangerous temperature for the electric water bath.
X.- Data collection
The raw data obtained from the experiment is presented in the following tables. The
tables contained the data of the initial volume3 of the 250 mL graduated cylinder with an
3
The initial volume is represented in the table as V0.
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uncertainty of ±5 % as well as the final volume4 of water displaced by CO2 gas
production, after a period of 25 min, for each of the five different concentrations of
glucose (5%, 10%, 15%, 20% and 25%).
Table 2. Volume of water displaced to determine CO2 (ml) production at 5% glucose concentration.
Volume of water displaced by CO2 gas (ml) at 5% glucose concentration
Trial 1
Trail 2
Trial 3
Trial 4
Trial 5
Time
V0 (ml)
Vf (ml) by
V0 (ml)
Vf (ml) by
V0 (ml)
Vf (ml) by
V0 (ml)
Vf (ml) by
V0 (ml)
(min)
±5%
CO2
±5%
CO2
±5%
CO2
±5%
CO2
±5%
±0.5
±5%
±5%
±5%
±5%
Vf (ml) by
CO2
±5%
5
13.00
26.00
83.00
97.00
15.00
25.00
90.00
102.00
16.00
29.00
10
13.00
47.00
83.00
121.00
15.00
52.00
90.00
123.00
16.00
53.00
15
13.00
64.00
83.00
141.00
15.00
72.00
90.00
143.00
16.00
72.00
20
13.00
71.00
83.00
151.00
15.00
80.00
90.00
159.00
16.00
80.00
25
13.00
81.00
83.00
161.00
15.00
92.00
90.00
164.00
16.00
89.00
Table 3. Volume of water displaced to determine CO2 (ml) production at 10% glucose concentration.
Volume of water displaced by CO2 gas (ml) at 10% glucose solution
Trial 1
Time
Trial 2
Trial 3
Trial 4
Trial 5
VO
Vf (ml) by
VO
Vf (ml) by
VO
Vf (ml) by
VO
Vf (ml) by
VO
Vf (ml) by
(min)
(ml)
CO2
(ml)
CO2
(ml)
CO2
(ml)
CO2
(ml)
CO2
±0.5
±5%
±5%
±5%
±5%
±5%
±5%
±5%
±5%
±5%
±5%
5
26.00
55.00
34.00
62.00
33.00
57.00
16.00
36.00
36.00
65.00
10
26.00
108.00
34.00
125.00
33.00
120.00
16.00
94.00
36.00
124.00
15
26.00
172.00
34.00
177.00
33.00
174.00
16.00
162.00
36.00
179.00
20
26.00
184.00
34.00
190.00
33.00
191.00
16.00
173.00
36.00
192.00
25
26.00
194.00
34.00
206.00
33.00
200.00
16.00
181.00
36.00
200.00
Table 4. Volume of water displaced to determine CO2 (ml) production at 15% glucose concentration.
Volume of water displaced by CO2 gas (ml) at 15% glucose solution
Trial 1
(ml)
CO2
(ml)
CO2
(ml)
CO2
(ml)
CO2
(ml)
CO2
±0.5
±5%
±5%
±5%
±5%
±5%
±5%
±5%
±5%
±5%
±5%
VO
Vf (ml) by
Trial 5
(min)
VO
Vf (ml) by
Trial 4
VO
VO
Vf (ml) by
Trial 3
Time
4
Vf (ml) by
Trial 2
VO
Vf (ml) by
The final volume displaced after each 5 min interval is represented in the table as V f.
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5
12.00
38.00
14.00
36.00
14.00
28.00
12.00
28.00
13.00
37.00
10
12.00
85.00
14.00
78.00
14.00
70.00
12.00
74.00
13.00
75.00
15
12.00
136.00
14.00
134.00
14.00
134.00
12.00
130.00
13.00
138.00
20
12.00
186.00
14.00
200.00
14.00
187.00
12.00
184.00
13.00
189.00
25
12.00
236.00
14.00
230.00
14.00
233.00
12.00
232.00
13.00
246.00
Table 5. Volume of water displaced to determine CO2 (ml) production at 20% glucose concentration.
Volume of water displaced by CO2 gas (ml) at 20% glucose solution
Trial 1
Time
Trial 2
VO
Vf (ml) by
(min)
(ml)
CO2
±0.5
±5%
±5%
5
32.00
40.00
10
32.00
15
Trial 3
Trial 4
Trial 5
VO (ml)
Vf (ml) by
VO
Vf (ml) by
VO
Vf (ml) by
VO
Vf (ml) by
±5%
CO2
(ml)
CO2
(ml)
CO2
(ml)
CO2
±5%
±5%
±5%
±5%
±5%
±5%
±5%
40.00
51.00
16.00
29.00
26.00
38.00
26.00
39.00
86.00
40.00
92.00
16.00
72.00
26.00
80.00
26.00
83.00
32.00
132.00
40.00
138.00
16.00
118.00
26.00
126.00
26.00
132.00
20
32.00
182.00
40.00
184.00
16.00
165.00
26.00
178.00
26.00
180.00
25
32.00
223.00
40.00
230.00
16.00
214.00
26.00
215.00
26.00
221.00
3
Table 6. Volume displaced of CO2 (cm ) production at 25% glucose concentration.
Volume of water displaced by CO2 gas (ml) at 25% glucose solution
Trial1
Time
Trial 2
Trial 3
Trial 4
Trial 5
VO
Vf (ml) by
VO
Vf (ml) by
VO
Vf (ml) by
VO
Vf (ml) by
VO
Vf (ml) by
(min)
(ml)
CO2
(ml)
CO2
(ml)
CO2
(ml)
CO2
(ml)
CO2
±0.5 s
±5%
±5%
±5%
±5%
±5%
±5%
±5%
±5%
±5%
±5%
5
12.00
35.00
32.00
48.00
54.00
70.00
34.00
60.00
14.00
34.00
10
12.00
64.00
32.00
88.00
54.00
106.00
34.00
92.00
14.00
73.00
15
12.00
108.00
32.00
124.00
54.00
145.00
34.00
126.00
14.00
104.00
20
12.00
134.00
32.00
144.00
54.00
174.00
34.00
153.00
14.00
133.00
25
12.00
160.00
32.00
175.00
54.00
203.00
34.00
179.00
14.00
161.00
XI.- Data processing
a) Calculating the production of CO2
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In order to obtain the amount of carbon dioxide (CO2) gas produced from the experiment
(which will be measured as volume), we must use the volume of water displaced during
the 25 min period each 5 min.
In the SI, the unit used to measure the volume of any substance is the cm 3. As a result,
the volume of carbon dioxide (CO2) gas recorded from the experiment must be
converted to cm3. The following equivalence must be used:
1 Cubic Centimeter (cm3) = 1 Milliliter
Example: For 5% glucose solution initial volume:
13.00 ml = 13.00 cm3
The volume of water displaced represents the amount of CO2 gas produced by the
fermentation of each of the five concentrations of glucose solution and yeast. First of all,
it must be calculated the difference between the volumes of CO 2 gas displaced each 5
min interval during the 25 min period. Therefore, we must subtract the final volume of
water displaced by CO2 at each 5 min interval, from the initial volume recorded by the
250 ml graduated cylinder (±5%). This procedure must be used for each of the samples
collected during the experiment. In order to obtain the difference between the volume
displaced each time interval and the initial volume, the following formula must be used:
d
(
)
Where:
d = Difference
= Initial volume
= Volume displaced at y- time interval
Example: For 5% glucose solution
d
(
)
d = 13.00 cm3
3
Table 7. Volume of CO2 (cm ) produced during a 25 min period at 5% glucose solution.
Volume of CO2 (cm3) produced during a 25 min period at 5% glucose solution.
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TIME
(min)
0
5
10
15
20
25
Trial 1
Trial 2
Trial 3
Trial 4
Trial 5
0.00
13.00
34.00
51.00
58.00
68.00
0.00
14.00
38.00
58.00
68.00
78.00
0.00
10.00
37.00
57.00
65.00
77.00
0.00
12.00
33.00
53.00
69.00
74.00
0.00
13.00
37.00
56.00
64.00
73.00
3
Table 8. Volume of CO2 (cm ) produced during a 25 min period at 10% glucose concentration.
Volume of CO2 (cm3) produced during a 25 min period at 10% glucose solution.
TIME
(min)
0
5
10
15
20
25
Trial 1
Trial 2
Trial 3
Trial 4
Trial 5
0.00
19.00
72.00
126.00
148.00
158.00
0.00
28.00
91.00
143.00
156.00
167.00
0.00
24.00
87.00
141.00
158.00
167.00
0.00
20.00
78.00
126.00
146.00
155.00
0.00
29.00
88.00
143.00
156.00
164.00
3
Table 9. Volume of CO2 (cm ) produced during a 25 min period at 15% glucose concentration.
Volume of CO2 (cm3) produced during a 25 min period at 15% glucose solution.
TIME
(min)
0
5
10
15
20
25
Trial 1
Trial 2
Trial 3
Trial 4
Trial 5
0.00
26.00
73.00
124.00
174.00
224.00
0.00
22.00
64.00
120.00
186.00
216.00
0.00
14.00
56.00
120.00
173.00
219.00
0.00
16.00
62.00
118.00
172.00
220.00
0.00
24.00
62.00
125.00
176.00
233.00
3
Table 10. Volume of C02 (cm ) produced during a 25 min period at 20% glucose concentration.
Volume of CO2 (cm3) produced during a 25 min period at 20% glucose solution.
TIME
Trial 1
Trial 3
Trial 4
Trial 4
Trial 5
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(min)
0
5
10
15
20
25
0.00
8.00
54.00
100.00
150.00
191.00
0.00
11.00
52.00
98.00
144.00
190.00
0.00
13.00
56.00
102.00
149.00
198.00
0.00
12.00
54.00
100.00
152.00
189.00
0.00
13.00
57.00
106.00
154.00
195.00
3
Table 11. Volume of CO2 (cm ) produced during a 25 min period at 25% glucose concentration.
Volume of CO2 (cm3) produced during a 25 min period at 25% glucose solution.
TIME
(min)
0
5
10
15
20
25
Trial 1
Trial 2
Trial 3
Trial 4
Trial 5
0.00
23.00
52.00
96.00
122.00
148.00
0.00
16.00
56.00
92.00
112.00
143.00
0.00
16.00
52.00
91.00
120.00
149.00
0.00
26.00
58.00
92.00
119.00
145.00
0.00
20.00
59.00
90.00
119.00
147.00
The following table shows the total final volume of CO2 gas displaced for each of the five
different concentrations of glucose solution.
3
Table 12. Final volume displaced of CO2 (cm ) production of each of glucose concentrations.
Final volumes of CO2 gas (cm3) of each of glucose concentrations
GLUCOSE
TRIAL 1 TRIAL 2 TRIAL 3 TRIAL 4 TRIAL 5
CONCENTRATION
5%
68.00
78.00
77.00
74.00
73.00
10%
168.00
172.00
167.00
165.00
164.00
15%
20%
25%
224.00
191.00
148.00
216.00
190.00
143.00
219.00
198.00
149.00
220.00
189.00
145.00
233.00
195.00
147.00
b) Calculating mean and standard deviation
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In order to analyze and to graph the data to discuss the hypothesis previously stated,
the mean and the standard deviation of each of the samples must be obtained. To
obtain the mean of the samples, the following formula must be used:
̄

̄ represents the mean of the values.

is all the values collected through the experiment.-

represents the number of items used in the sample.
Example: Taking the data collected for 5% glucose concentration at 5 min interval:
̄
̄
cm3
The reason of using standard deviation is because in the laymen’s terms, the standard
deviation represents a number which tells how far from the mean a data value is with
respect to how far the other data values are from the mean.
∑
S= √
((∑ )
)
Example: Taking the data collected for 5% glucose concentration at 5 min interval.
S=
√
∑
((
)
S = 1.52
)
n
x
̄
1
2
3
4
5
13.00
14.00
10.00
12.00
13.00
62.00
169.00
196.00
100.00
144.00
169.00
778.00
2
c) Dispersion graphs
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In order to analyze the data obtained by the standard deviation values of each of the five
different sugar concentrations (5%, 10%, 15%, 20% and 25%), it is necessary to plot a
dispersion graph. These graphs will show the correlation between each time (min)
period interval and the mean volumes of CO2 gas (cm3) produced during yeast
fermentation. Furthermore, the graphs will show the error bars which are helpful to
appreciate the standard deviation calculated for each of the five sugar concentration in a
graphical form. The error bars state how far from the mean a value is with respect to
how far the other values are from the mean.
In addition, the line of logarithmic regression can be appreciated from the dispersion
graph. This line shows the logarithmic relationship between each mean value obtained
at each 5 min. interval. From the graphs, the correlation coefficient of Pearson (R2) can
be appreciated. This coefficient is necessary to determine in a mathematical way the
correlation strength between the mean volumes of CO2 gas displaced.
In order to have an accurate analysis form the graphs, the maximum value of 250 cm3
was chosen to be plot in the y-axis. The following tables and graphs show the standard
deviation, the mean values and the regression line for each glucose concentration (5%,
10%, 15%, 20% and 25%):
Table 13. Mean and standard deviation of the data collected of CO2 gas produced at 5% glucose
concentration
TIME
(min)
0
5
10
15
20
25
TRIAL 1
Volume of
CO2
TRAIL 2
Volume of
CO2
TRAIL 3
Volume of
CO2
TRIAL 4
Volume of
CO2
TRAIL 5
Volume of
CO2
(cm )
(cm )
(cm )
(cm )
(cm )
0.00
13.00
34.00
51.00
58.00
68.00
0.00
14.00
38.00
58.00
68.00
78.00
0.00
10.00
37.00
57.00
65.00
77.00
0.00
12.00
33.00
53.00
69.00
74.00
0.00
13.00
37.00
56.00
64.00
73.00
3
3
3
3
̄
S
0.00
12.40
35.80
55.00
64.80
74.00
0.00
1.52
2.17
2.92
4.32
3.94
3
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Graph 1. Mean and standard deviation of the data collected for 5% glucose concentration
GLUCOSE 5% - CO2 PRODUCTION
250
y = 38.66ln(x) - 50.84
R² = 0.99
CO2 PRODUCTION (cm3)
200
150
Glucose 5%
Tendency line
100
50
0
0
5
10
15
20
25
30
TIME (min)
From the previous graph it can be observed the rate of CO2 gas released in fermentation
for the 5% glucose solution with yeast. The graph shows the mean values of each trial
performed for the 5% glucose concentration.
When using the 5% glucose concentration, the error bars show that there was a very
small difference between the production of CO2 gas collected in each trial. The
fermentation rate in each trial for the 5% glucose concentration did not differ
significantly. The standard deviation error bars show that the difference in the values
obtained for the production of CO2 gas collected in each trial was very small. This
means that the results of obtained were very near between them which gives a more
accurate information.
Furthermore, the tendency line shows the correlation between the values obtained in
each 5 min interval. As time increases, there is an increased in the production of CO 2
gas. Visually, it can be observed that there is a very strong positive correlation between
15
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the means. From the graph, it can pointed that the correlation coefficient (R 2) is 0.99,
which means that as the coefficient of correlation obtained is approaching to 1, there is a
very strong correlation, and there is not any outlier. The production of CO 2 gas released
during fermentation was almost the same in each trial. There was not a significant
difference in the rate of CO2 released in each trial for 5% glucose concentration.
Table 14. Mean and the standard deviation of the data collected for the CO 2 gas produced at 10%
glucose concentration
TIME
(min)
0
5
10
15
20
25
TRIAL 1
TRIAL 2
Volume
of CO2
(cm3)
Volume
of CO2
(cm )
0.00
29.00
82.00
146.00
158.00
168.00
0.00
28.00
91.00
143.00
156.00
172.00
TRAIL 3
Volume
of CO2
3
TRIAL 4
TRIAL 5
Volume
of CO2
Volume
of CO2
(cm )
(cm )
(cm )
0.00
24.00
87.00
141.00
158.00
167.00
0.00
20.00
78.00
146.00
157.00
165.00
0.00
29.00
88.00
143.00
156.00
164.00
3
3
̄
S
0.00
26.00
85.20
143.80
157.00
167.20
0.00
3.94
5.17
2.17
1.00
3.11
3
Graph 2. Mean and standard deviation of the data collected for 10% glucose concentration
GLUCOSE 10% - CO2 PRODUCTION
250
CO2 PRODUCTION (cm3)
200
y = 92.36ln(x) - 121.23
R² = 0.97
150
Glucose 10%
Tendency line
100
50
0
0
5
10
15
20
25
30
TIME (min)
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The previous graph shows the rate of fermentation process for the 10% glucose solution
with yeast. It shows the mean values of each trial performed for the 10% glucose
concentration in order to make a comparison between the production CO 2 released in
each of the trials.
From the graph it can be appreciated that the standard deviation error bars show no
significant difference. The fermentation rate in each trial of 10% glucose concentration
did not differ significantly. This means that the results of obtained are more accurate.
Visually, the tendency line of the graph shows the correlation between the values
obtained in each 5 min interval during a period of 25 min. It can be observed that there
is a strong positive correlation between the means from each trial in respect to the
tendency line.
For 10% glucose solution there was a mean between 150 cm 3 and 200 cm3 of CO2
released. As time increases, there is an increased in the production of CO 2 gas.
According to correlation coefficient (R2) given, which is 0.97; this means that as the
coefficient of correlation obtained is approaching to 1, there is a very strong correlation.
In addition there is not the presence of any outlier. There was not a significant difference
in the rate of CO2 released in each trial for 10% glucose concentration.
Table 15. Mean and the standard deviation of the data collected for the production of CO 2 at 15% glucose
concentration
TIME
(min)
TRIAL 1
TRIAL 2
TRAIL 3
TRIAL 4
TRIAL 5
Volume
of CO2
(cm3)
Volume
of CO2
(cm3)
Volume
of CO2
(cm3)
Volume
of CO2
(cm3)
Volume
of CO2
(cm3)
0
5
10
15
20
25
0.00
26.00
73.00
124.00
174.00
224.00
0.00
22.00
64.00
120.00
186.00
216.00
0.00
14.00
56.00
120.00
173.00
219.00
0.00
16.00
62.00
118.00
172.00
220.00
0.00
24.00
62.00
125.00
176.00
233.00
̄
S
0.00
20.40
63.40
121.40
176.20
222.40
0.00
5.18
6.15
2.97
5.67
6.58
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Graph 3. Mean and standard deviation of the data collected for 15% glucose concentration
GLUCOSE 15% - CO2 PRODUCTION
250
y = 124.66ln(x) - 199.23
R² = 0.9
CO2 PRODUCTION (cm3)
200
150
Glucose 15%
Tendency line
100
50
0
0
5
10
15
20
25
30
TIME (min)
The graph presents the rate of fermentation process for the 15% glucose solution with
yeast. It shows the mean values of each trial performed for the 15% glucose
concentration in relation to the production CO2 released in each trial.
Visually, the graph shows that the standard deviation error bars show a very small
difference between each trial. The fermentation rate in each trial of 15% glucose
concentration did not differ significantly. In addition, the tendency line shows the
correlation between the values obtained during a period of 25 min. There is a strong
positive correlation between the means obtained from each trial and the tendency line.
The 15% glucose solution shows a mean between 200 cm 3 and 250 cm3 of CO2 gas
released. Moreover, the as there is a strong correlation, it can be observed that as time
increases, there is an increased in the production of CO2 gas. From the graph, it can be
remarked that the correlation coefficient (R2) is 0.94; the coefficient of correlation
obtained is approaching to 1, so there is a very strong correlation. There was not a
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significant difference in the rate of CO2 released in each trial for 10% glucose
concentration.
Table 16. Mean and the standard deviation of the data collected for the production of CO 2 at 20% glucose
concentration
TIME
(min)
0
5
10
15
20
25
TRIAL 1
TRIAL 2
TRAIL 3
TRIAL 4
TRIAL 5
Volume
of CO2
(cm3)
Volume
of CO2
(cm3)
Volume
of CO2
(cm3)
Volume
of CO2
(cm3)
Volume
of CO2
(cm3)
0.00
8.00
54.00
100.00
150.00
191.00
0.00
11.00
52.00
98.00
144.00
190.00
0.00
13.00
56.00
102.00
149.00
198.00
0.00
12.00
54.00
100.00
152.00
189.00
0.00
13.00
57.00
106.00
154.00
195.00
̄
S
0.00
11.40
54.60
101.20
149.80
192.60
0.00
2.07
1.95
3.03
3.77
3.78
Graph 4. Mean and standard deviation of the data collected for 20% glucose concentration
GLUCOSE 20% -CO2 PRODUCTION
250
y = 110.63ln(x) - 182.07
R² = 0.94
CO2 PRODUCTION (cm3)
200
150
Glucose 20%
Tendency line
100
50
0
0
5
10
15
20
25
30
TIME (min)
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The graph shows the rate of fermentation process for 20% glucose solution with yeast. It
shows the mean values of each trial performed for the 20% glucose concentration in
relation to the production CO2 released in each trial.
The graph shows that from the standard deviation error bars there is a very small
difference in CO2 gas production in fermentation process of each trial. The fermentation
rate in each trial of 20% glucose concentration did not differ significantly. From the
tendency line shows the correlation between the values obtained, meaning that there is
a strong positive correlation between the means obtained from each trial. This
correlation observed means that as time increases, there is an increased in the
production of CO2 gas; and such increased was not very different in the rate of reaction
of each of the trials that were carried out.
Mathematically, the correlation coefficient obtained was 0.94; which is a value
approaching to 1, so there is a very strong correlation. There was not a significant
difference in the rate of CO2 released in each trial for 20% glucose concentration.
Table 17. Mean and the standard deviation of the data collected for the production of CO 2 at 25% glucose
concentration
TIME
(min)
0
5
10
15
20
25
TRIAL 1
TRIAL 2
TRAIL 3
TRIAL 4
TRIAL 5
Volume
of CO2
(cm3)
Volume
of CO2
(cm3)
Volume
of CO2
(cm3)
Volume
of CO2
(cm3)
Volume
of CO2
(cm3)
0.00
23.00
52.00
96.00
122.00
148.00
0.00
16.00
56.00
92.00
112.00
143.00
0.00
16.00
52.00
91.00
120.00
149.00
0.00
26.00
58.00
92.00
119.00
145.00
0.00
20.00
59.00
90.00
119.00
147.00
̄
S
0.00
20.20
55.40
92.20
118.40
146.40
0.00
4.38
3.29
2.28
3.78
2.41
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Graph 5. Mean and standard deviation of the data collected for 25% glucose concentration
GLUCOSE 25% - CO2 PRODUCTION
CO2 PRODUCTION (cm3)
250
200
y = 77.52ln(x) - 112.48
R² = 0.97
150
Glucose 25%
Tendency line
100
50
0
0
5
10
15
20
25
30
TIME (min)
The previous graph represents the rate of fermentation process for 25% glucose
solution concentration with yeast. It shows the mean values of each trial performed for
the 25% glucose concentration in relation to the production CO 2 released in each trial.
The standard deviation error bars presented in the graph show that there was no
significant difference in CO2 gas production in fermentation process of each trial.
The tendency line shows the correlation between the values obtained. It can be
observed that there is strong positive correlation between the means obtained from each
trial of 25% glucose concentration. Mathematically, the correlation coefficient was 0.971;
a value approaching to the value of 1, meaning that there is a very strong correlation.
There was no significant difference in the rate of CO2 released in each trial carried out
for 25% glucose concentration. It can be observed that as time increases, the production
of CO2 gas increases as well; and such increased was not very different in the rate of
reaction of each of the trials that were carried out.
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d) Calculating mean values and standard deviation for final production of CO2 of each
glucose concentration.
In order to compare the effect of the five different concentrations of glucose solution
(5%, 10%, 15%, 20% and 25%) in the fermentation process of yeast, it is necessary to
calculate and to graph the mean values of the final volume of CO 2 released for each of
the five concentrations.
Table 18. Values of mean and the standard deviation of final production of CO 2 for each glucose
concentration.
Glucose
Concentration
TRIAL 1
TRIAL 2
TRAIL 3
TRIAL 4
TRIAL 5
Volume
of CO2
(cm3)
Volume
of CO2
(cm3)
Volume
of CO2
(cm3)
Volume
of CO2
(cm3)
Volume
of CO2
(cm3)
5%
10%
15%
20%
68.00
168.00
224.00
191.00
78.00
172.00
216.00
190.00
77.00
167.00
219.00
198.00
74.00
165.00
220.00
189.00
25%
148.00
143.00
149.00
145.00
̄
S
73.00
164.00
233.00
195.00
74.00
167.20
222.40
192.60
3.94
3.11
6.58
3.78
147.00
146.40
2.41
Graph 6. Mean and standard deviation of the final amount CO2 gas released for each glucose concentration.
CO2 PRODUCTION
CO2 PRODUCTION (cm3)
250
222.40
200
192.60
167.20
150
5%
146.40
10%
15%
100
20%
50
74.00
25%
0
5%
10%
15%
20%
25%
GLUCOSE CONCENTRATION
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“The Effect of Different Concentrations of Glucose in the Anaerobic Respiration by Yeast
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As it can be seen from the previous graph, the 5% glucose concentration was the
concentration which produced the less amount of carbon dioxide gas (CO 2) during the
experiment, with 74.00 cm3. In addition, it can be observed that there was an increased
in the production of CO2 as the concentration of glucose increased until the 15% glucose
concentration, which showed the maximum production of CO2.
The greatest production of CO2 gas released was presented at 15% glucose
concentration. However, from 15% glucose concentration it was a significant change in
the production of CO2 gas for 20% and 25% glucose concentration; for such
concentrations of glucose, the volume of CO2 gas released started decreasing in a
significant way. From 5% to 15% glucose concentration, there was an increased in the
volume of CO2 production as the concentration increased. However, as the
concentration of glucose was increasing from 20% to 25%, the CO2 gas released was
decreasing.
In addition, from the standard deviation error bars, we can observe that for each of the
different concentrations of glucose (5%, 10%, 15%, 20%, 25%) there was a relatively
small difference from the data collected for the five trials carried out for each sugar
concentrations. This means that the data collected of CO 2 gas released for each of the
five concentrations and their respectively trials were constant during fermentation
process.
e) Calculating ANOVA-test.
Visually, we can observe from graph 7 that the means of the final volume of CO 2 gas
released from each glucose concentration are different to one another. However, in
order to state whether or not the means of the final volumes of CO 2 gas released for
each concentration differ to one another, it is necessary to calculate ANOVA – test5.
5
In order to carry out ANOVA – test, a normality test was previously carried out in order to ensure that the set of data
chosen for ANOVA-test was well modeled by a normal distribution.
23
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In order to perform ANOVA – test, it is necessary to group the data in a separate table.
This data refers to the final volume displaced of CO2 gas after the 25 min. period for
each sugar concentration.
Table 19. Final volume of CO2 gas displaced for each glucose concentration after a 25 min. period.
Final volume displaced of CO2 gas (cm3) after 25 min period
Groups
Trial 1
Trial 2
Trial 3
Trial 4
Trial 5
5% glucose
68.00
78.00
77.00
74.00
73.00
10% glucose
168.00
172.00
167.00
165.00
164.00
15% glucose
224.00
216.00
219.00
220.00
233.00
20% glucose
191.00
190.00
198.00
189.00
195.00
25% glucose
148.00
143.00
149.00
145.00
147.00
The null hypothesis (H0) as well as the alternative hypothesis (H1) must be stated. After
calculating ANOVA – test:
If F < FC then H0 is accepted.
Hypothesis:
H0= There is no difference between the volume of CO2 gas released in each sample
treated with each glucose concentration.
H1= There is a difference between the volume of CO2 gas released in each sample
treated with each glucose concentration.
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“The Effect of Different Concentrations of Glucose in the Anaerobic Respiration by Yeast
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SUMMARY
Table 20. ANOVA – test summary.
Groups
5%
Glucose
10%
Glucose
15%
Glucose
20%
Glucose
25%
Glucose
N0. of
measurements
5.00
Sum
Mean
Varience
370.00
74.00
15.50
5.00
836.00
167.20
9.70
5.00
1112.00
222.40
43.30
5.00
963.00
192.60
14.30
5.00
732.00
146.40
5.80
ANOVA
Table 21. ANOVA – test.
Source of
variation
Between
groups
Within
groups
Sum of
squares
62939.84
Freedom
Degrees
4.00
Mean of
squares
15734.96
354.40
20.00
17.72
Total
63294.24
24.00
F
887.98
P-value
3.31E-22
F – crit.
2.87
As F is equal to 887.98 and Fc equals to 2.87, the value of F is greater than Fc then H0 is
not accepted, 887.7 >2.87. So, there is a difference between the volumes of CO 2 gas
released in each sample treated with each glucose concentration.
XII.- Conclusion
As it could be observed in the information presented in the previous tables and graphs,
the hypothesis previously stated was not correct. At the moment of analyzing the raw
data, it could be noticed that the production of carbon dioxide gas by the fermentation of
glucose was increasing while the glucose concentration was increasing. However, this
increase in CO2 gas production was present only when using 5%, 10% and 15% glucose
concentrations; but when fermenting yeast at 20% and 25% glucose concentrations, the
production of carbon dioxide gas started to decrease considerably.
25
“The Effect of Different Concentrations of Glucose in the Anaerobic Respiration by Yeast
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When using 5% glucose concentration, there was a mean of 74.00 cm 3 of carbon
dioxide (CO2) gas production. This concentration of glucose sugar was the one
producing the less volume of CO2 gas released. Furthermore, analyzing graph 1 with
each of the values collected from the five trials of sample concentration; it could be
observed by means of the standard deviation error bars that there was a very small
difference between the production of CO2 gas collected for each trial, giving a more
accurate information. In addition, the R2 coefficient, 0.99, approached to 1, there was a
very strong correlation, and there were not any outlier. So the production of CO 2 gas
released during fermentation was almost the same in each trial.
For the 10% glucose concentration, it could be observed a significant difference
between the mean of CO2 of 5% glucose concentration, releasing a mean volume of
167.20 cm3. The amount of such gas increased at a 10% concentration. In addition, from
graph 2 it could be appreciated that the standard deviation error bars show no significant
difference. The fermentation rate in each trial of 10% glucose concentration did not differ
significantly. With a correlation coefficient (R2) of 0.97, there was a very strong positive
correlation.
Analyzing the data provided by the samples of 15 % glucose concentration, it could be
seen that at this concentration, there was a greater production of carbon dioxide with a
mean of 226.40 cm3 released. At this concentration, glucose fermented yeast at a higher
rate. Furthermore, it was showed in graph 3, by means of the standard deviation, that
there was a small difference on the amount of CO2 released between the data values
collected from each trial. Moreover, the correlation coefficient was 0.94; giving a very
strong positive correlation. There was not a significant difference in the rate of CO 2
released in each trial for 10% glucose concentration.
However, the refutation of the hypothesis stated is presented when analyzing the data
from the 20% glucose concentration. At this concentration, the volume of CO2 released
decreased in a significant way. For this concentration was expected a greater volume
released of such gas; however, it happens the other way around, with a decrease in the
released of CO2. Furthermore, there is present the greater difference in the volume
produce of CO2 of each of the trials of the sample, with a mean of 192.70 cm 3.
26
“The Effect of Different Concentrations of Glucose in the Anaerobic Respiration by Yeast
/ Mayo 2012
When analyzing the results of the 25% glucose concentration, it was a greater
decreased on the production of CO2. For this concentration, and based on the
hypothesis, it was expected the major production of CO2; however, there was a greater
decreased on CO2 with reference to the 20% concentration. In addition to these results,
the standard deviation error bars presented in the graph 5 showed that there was no
significant difference in CO2 gas production in fermentation process of each individual
trial. Mathematically, the correlation coefficient was 0.97, meaning that there was a very
strong positive correlation. There was no significant difference in the rate of CO2
released in each trial carried out for 25% glucose concentration.
As it was shown in the data collected from the experiment the effect of increasing the
concentration of glucose with respect to the volume of CO2 released was not as it was
expected from the hypothesis stated. At the beginning, as the concentration from 5%
increased to a 10% glucose concentration; however as the concentration increased from
15% to 25%, there was a decreased in the volume of carbon dioxide gas released.
According to Damon, McGonegal, and Ward, (2009) a reason for the decreased on
carbon dioxide volume released from yeast respiration, it could be because when
increasing the concentration of a substance, there is an increased of molecular
collisions; however, as yeast contains certain types of enzymes, such enzymes have a
certain limit to which they can work at a maximum rate. As a result, if we continue
increasing the concentration of substrate, there will be a point in which the enzymes will
be working as far as possible until they cannot work efficiently, so the rate of reaction
starts decreasing.
Another reason for the decreased of the volume of CO 2 released as the concentration of
glucose was increasing is because as the experiment was carried out within a closed
system, the production of carbon dioxide gas as the concentration of glucose was
increasing, it could have killed the yeast inside the flask.
27
“The Effect of Different Concentrations of Glucose in the Anaerobic Respiration by Yeast
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XIII.- Evaluation
Along the experiment it was possible to obtain reliable data when following cautiously
the method previously designed step by step with the objective of avoiding any possible
problem in terms of the control of variables. In addition, a set of five trials were
performed for each sugar concentration (5%, 10%, 15%, 20% and 25%) in order to
gather current and reliable data for the analysis. However, there will be always problems
that can arise when performing the experiment which can be improved for future
repetitions of the experiment.
The data gathered from the production of carbon dioxide (CO2) by means of the final
water displacement of the 250 ml graduated cylinder (±5 %), it can be 80% accurate due
to the lost of CO2 present when mixing the substances and at the moment of closing the
flasks by means of the rubber stopper; a reason why this happened is because when
mixing the glucose solution with yeast, the reaction was very fast and there is a loss in
carbon dioxide gas from the closed system to the environment. However, the
fermentation process was carried out in a way in which it was able to obtain quantitative
data with respect to the volume of carbon dioxide gas released.
In addition, when performing this experiment a problem aroused related with
temperature. As it was pointed out, the optimum temperature to carry out the
fermentation reaction was 37°C; however, the room temperature form the laboratory
affected the optimum temperature set on the electric water bath. Even though
precautions were taken in terms of maintaining the optimum temperature as the use of
the incubator and the use of the electric bath, the control of the temperature was difficult
to maintain due to the opening of the electric water bath.
Besides that, another possible weakness of the experiment was the period of time
considered for the collection of data during the fermentation process. As the data was
collected at 5 min intervals during a 25 min period due to the laboratory conditions, the
data gathered was limited to a fraction of the process. As a result, this can be
considered as a limitation for the overall analysis since it can probably affect the
accuracy of the data for the approval of the hypothesis.
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XIV.- Improvements
An improvement for the experiment can be the fact of increasing the period of time for
fermentation. As the data was collected during a 25 min period, the data collected
corresponds only to a fraction of the complete fermentation process. It would be best to
record the data until the fermentation process has ended, in order to have more
accurate information about the rate of CO2 released.
Another improvement in order to enhance the experiment could be to have a better
control over the room temperature from the laboratory where the experiment was
performed. Even though some precautions were taken with respect to maintain the
optimum temperature of 37°C as the use of the incubator and the electric water bath, the
opening of the water bath was a limitation because the 125 ml flasks (±5 %) in which the
fermentation process was taking place were exposed to the room temperature from the
laboratory.
XV.- Bibliography
Clark, Jim. (2002). The effect of concentration on reaction rates. Web. 24 Oct 2011.
<http://www.chemguide.co.uk/physical/basicrates/concentration.html
Damon, Alan, McGonegal, Randy, Tosto, Patricia, & Ward, William. (2009). Higher level
Biology developed specifically for the IB diploma. Pearson Education, Inc.
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