a) Enzymes speed up the rate of chemical reactions without being used up by first binding to the reactants (substrate). The location of the binding is called the enzyme's active site. This bond lowers the activation energy (the energy needed to start the reaction), making the reaction occur faster. Enzymes' effectiveness can be affected by pH, temperature, and salinity. The reaction tends to occur faster if the concentration of enzymes or substrates is increased, but there is a point when the solution becomes saturated with either enzymes or substrates and cannot work any faster. The enzyme we will be using on this lab is cellobiase, which breaks down cellobiose - a sugar derivative of cellulose, a polysaccharide found in plant cell walls. The biofuel agency uses enzymes such as cellobiase to break down cellulose in plant matter and convert it to glucose. Glucose can then be converted to ethanol by microbial fermentation. Ethanol can then be used as an energy source to power certain motors and engines.
b) The purpose of this lab is to experience first hand in the classroom what biofuel companies do on a massive scale. Biofuel companies are constantly experimenting to find the most efficient way to make biofuels - and the method we will use in this experiment is only one method out of many.
c) We will use pipetting techniques to carefully and accurately transfer enzymes, buffers, and substrates to the solution. On Day #1, we will transfer a little bit of the solution at various time points to another test tube with a strong base to stop the reaction. The base will also turn p-nitrophenol (a product of the reaction) yellow, so we can judge how much product (including the glucose) has been created. On Day #2, we will have to carefully grind up mushrooms and add the mushroom extract to the reaction and measure how this affects the speed of the reaction.
d) I predict that, as time goes on, more product will be produced from the reaction. Also, I think the mushroom, which contains more enzymes, including cellobiase, will speed up the reaction rate. The variable of this experiment is the mushroom. The control is the amount of product produced under normal circumstances (Day #1).
Results/Observations:
The solution from Day #1 turned more yellow over time (the first cuvette was the lightest and the last cuvette, the darkest). The solution with the mushroom (Day #2) also turned darker over time, only faster.
Discussion:
a) The solution from Day #1 turned more yellow over time (the first cuvette was the lightest and the last cuvette, the darkest). This indicates that more product was produced over time. On Day #2, the mushroom turned darker faster, indicating that the reaction was occurring faster. This is probably because the mushrooms contain more enzymes, such as celliobiase, which can speed up the reaction to an extent. There is a limit to how many enzymes are effective, but in the case of Day #2, the extra enzymes did help speed up the reaction.
b) Possible sources of error...
- Incorrect measuring with the pipettes
- Contamination of the solution(s)
- Timing errors
Excellent - A!
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