Graph (1)
This graph presents the change in level of water in the cylinder ±1 cm3 every 300 seconds, using the four types of sugar.
Data Processing
To measure the rate of reaction due to the fermentation of yeast using different types of sugars, the volume of the carbon dioxide should be calculated first. We measure it using this formula:
Carbon dioxide volume = final reading of the level of water- initial reading of the level of water
Table (2)
This table shows the volume of the carbon dioxide produced in cm3 ±2 using all the four sugars (Glucose, Lactose, Maltose and Sucrose).
The uncertainty is ±2 because here we added the uncertainty twice, because we used both the initial and the final uncertainties. (Each one is ±1)
Graph (2)
This graph represents the volume of carbon dioxide produced using each type of sugar over a period of 1800 seconds.
To calculate the rate of the reaction, we use a formula:
Rate of the reaction=
Table (3)
This table shows the rate of reaction using each type of sugar.
Graph (3)
This graph shows the rate of the reaction for each type of sugar used. It shows differences in the rate of the reaction where it is very clear that glucose has the highest rate of the reaction, then maltose, and lactose respectively.
Conclusion and Evaluation
Yeast can metabolize some foods. For an organism to make use of a potential source of food, it must be capable of transporting the food into its cells. It must also have the proper enzymes capable of breaking down the chemical bonds of the food in a useful way. Sugars are essential to all living organisms. Yeast is capable of using some, but not all sugars as a food source. Yeast can metabolize sugar in two ways, aerobically, with the presence of oxygen (respiration), or anaerobically, without oxygen (fermentation).
The overall process of fermentation is to convert glucose sugar (C6H12O6) to alcohol (CH3CH2OH) and carbon dioxide gas (CO2). The reactions within the yeast cell which make this happen are very complex but the overall process is as follows:
C6H12O6 -> 2 (CH3CH2OH) + 2(CO2) + Energy (ATP)
Sugar -> Alcohol + Carbon dioxide gas + Energy
(Glucose) (Ethyl alcohol)
As it is shown in table (1) the level of water was changed using glucose then the maltose then lactose respectively, the water level using sucrose remained unchanged.
As shown before, the volume of carbon dioxide produced using each type of sugar as well, also, the fermentation of yeast using glucose, produced the largest volume of carbon dioxide then maltose then lactose respectively with no production of carbon dioxide in the sucrose. The rate of reaction using glucose was (0.29 cm3 s-1), Maltose 0.011 cm3 s-1, Lactose 0.003 cm3 s-1.
Sources of error
1. The amount of yeast used with each type of sugar may affect the rate of the reaction.
2. When pouring the solutions into the four flasks the volume measured may vary as some drops may stay on the glass surface of the measuring tool.
3. The temperature was not controlled throughout the experiment.
4. There may be some leakage of carbon dioxide.
5. Errors in reading the level of water in the inverted cylinder may affect our calculations.
Improvements
1. Take the reading more than one time.
2. Using thermometer throughout the experiment to watch it and unify it as much as possible.
3. Repeat the experiment more than one time in order to take the average reading and to have mo precise result.
4. Try to weigh the same amount of used yeast in each trial. 5. Close all the tubes tightly and any source of leakage in the experiment.
by
ayahkhader (student)
