Lab 5 Alcoholic fermentation PDF

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CHEM 354-03 Lab 5: Alcoholic Fermentation of Yeast Date performed: 02/05/2020 Date Submitted: 02/12/2020 Group 2:

Introduction: The purpose of this lab was to determine if yeast can metabolize different sugars and how well the sugars are metabolized. This is determined by measuring how much C O 2 is produced. Yeast is a facultative anaerobe, which means that it can metabolize sugar and produce ATP with the absence of oxygen. Without oxygen, cells can make ATP utilizing glycolysis and fermentation. This anaerobic method doesn’t produce as much ATP as aerobic cellular respiration; however it is effective when no oxygen is present. Each member of the group was assigned a different sugar concentration sample and one of two temperatures to place their sample in. A balloon secured to the top of the reaction vial which was purposed to catch the C O2 that was released. The circumference of the balloon and the depth of the C O 2 were recorded in order to determine how well the sugars were metabolized. Materials and Methods: 15mL 8% maltose at 37℃

37°C water bath

15mL 8% fructose at 45℃

45°C water bath

15mL 8% fructose at 37℃

water

15mL 4% sucrose at 45℃

pre-measured yeast sample

15mL galactose

1 large test tube per sample

1 water balloon per test tube

sharpie

Each lab member was pre-assigned a sugar, a concentration, and a water bath temperature. Each lab member then performed an individual experiment, consisting of gathering the materials and building the test tube contents. The assigned sugar and pre-measured yeast were put in the test tube and shaken to dissolve the yeast into solution. A balloon was then utilized to seal the top of the test tube, and the tube was placed in the proper water bath. A stopwatch was started in order to keep account of the time which was needed in order to obtain readings at each time increment. Every ten minutes, for the next thirty minutes, each test tube was observed, and the measurements of bubble depth and balloon circumference were measured and recorded. At the end of the experiment, the results were reported at the front of the laboratory.

Results and Discussion:

Depth of

Balloon circumference (in cm):

C O2 bubbles at time mark (in cm):

Sample

10 min.

20 min.

30 min.

0 min.

10 min.

20 min.

30 min.

8% maltose @ 37℃

1.85

5.95

6.40

4.00

5.00

10.00

12.55

8% fructose @ 45℃

5.58

6.65

7.45

4.00

8.50

11.00

11.50

8% fructose @ 37℃

3.00

-

-

4.00

6.00

-

-

4% sucrose @ 45℃

9.00

9.70

10.00

4.00

10.00

13.00

13.30

Table 1: Represents the depth of the CO2 and the balloon circumference for each sugar tested at different temperatures. The data was collected every 10 minutes for a 30-minute time period. Each member of the group tested for one of the following: 8% maltose at 37°C, 8% sucrose at 45°, 8% fructose at 37°C, and 4% sucrose at 45°C. The boxes highlighted indicate that the measurement included bubbles that fed into the balloon.

Carbon dioxide accumulated in all the sugar samples when yeast was added into the test tubes. For the 8% fructose at 37°C sample, carbon dioxide production was no longer quantized after the ten-minute mark because the balloon had burst. There are several reasons why the balloon could have burst. Either the balloon was not properly attached to the tube, the balloon was defective beforehand, or the balloon was not stretched out well enough. For the other sugars in Table 1, the carbon dioxide bubbles rose into the balloon; since the circumference of the balloon was measured every ten minutes, this factor was considered by measuring the circumference with the largest diameter of the balloon. Analyzing the change in depth of carbon dioxide bubbles produced by each sample, it was determined that sucrose had the highest rate of fermentation due to its digestive reaction. The enzyme invertase that is present in yeast is used to break up sucrose, a disaccharide (two sugars), into glucose and fructose. Fructose must then undergo isomerization to become glucose. These two reactions are what likely caused the high production rate of carbon dioxide. Overall, the rate of fermentation for each sugar can be affected by many factors such as: substrate concentration, enzyme concentration and temperature. Conclusion: The purpose of this lab was to analyze the rate of C O2 production given the sugar sample’s characteristics. Each group member was assigned a different sample that differed in the kind of sugar, the concentration of sugar in the sample, or temperature of the water bath the sample was to be placed in. The circumference of the balloon and the depth of the carbon dioxide bubbles measured throughout the experiment. Two discrepancies occurred during the experiment that should be noted. First, the C O2 bubbles fed into some of the balloons. When this occurred, the depth of the bubbles was measured including the amount visible inside the balloon. Also, throughout the experiment, in both the group level as well as the class level, many samples’ balloons burst and therefore the testing was cut short. The values listed in Table 1, are the experimental values that were obtained in the experiment and no sample was tested twice. Given

the results in Table 1, the conclusion drawn from the three samples that completed the entire thirty minutes is that the rate of C O 2 production is greater at the beginning of the yeast-sugar reaction than it is later in the reaction. This is proven by comparing the rate at ten to twenty minutes and twenty to thirty minutes. This supports the conclusion that yeast metabolizes the sugars at a faster rate when it is initially placed in solution than it does after the twenty-minute mark. This can be explained because rate is dependent on concentration. The higher the concentration of sugar the faster the rate. The initial concentration of sugar was higher and therefore the rate of metabolization was faster....