Planning:
Our experiment involves seeing what affect an enzyme, called trypsin, has on a protein, called casein, in a milk solution. The first thing we must do is to put different concentrations of trypsin into milk solution, and see how long it takes for each solution to turn transparent. We will time how long it takes it each solution to go transparent. We will then use different pH buffer solutions, in order to change the pH of the reaction, and see how trypsin will react in each solution.
I predict that the reaction rates will be higher with alkalis,
as we have learnt that Trypsin does not react well in
acidic conditions.
We must bear in mind the factors which affect the reaction
rates of enzymes:
- Concentration of the substrate - the amount of the protein
will determine the amount of time taken for it to be broken
down by the enzyme, (trypsin in this case).
2)Temperature - All enzymes have an optimum temperature, at
which they work best at. If overheated, they can become
denatured forever.
- The pH - All enzymes work best at a certain pH, (for example,
trypsin works best at a pH of 8).
4) The concentration of the enzyme - The amount of time taken
for the substrate to be broken down depends on the amount of enzyme.
Method:
The first thing we did was putting different concentrations of
trypsin into a 10% milk solution. We then timed how long it
took for each solution to turn from opaque/translucent to
transparent. This gave us a general idea of what conditions the
enzyme worked best in. Our next task was to see how trypsin
would react with different pH solutions. This was accomplished
by adding different pH buffer solutions to the milk solutions.
Once again, we timed how long it took for each solution to turn
see through.
Prediction:
My prediction for this experiment is that the average time will decrease as the pH increases (from 3 to 15). I also think that, as the concentration of trypsin increases, the time will decrease.
Results:
Concentration 1/Time
of trypsin
0 0
0.1 0.04
0.2 0.1
0.3 0.134
0.4 0.157
0.5 0.187
0.6 0.232
0.7 0.246
0.8 0.283
0.9 0.3
1.0 0.311
pH Average time/ mins
3 No reaction
5 No reaction
7 0.38
9 4.21
11 3.62
13 1.79
15 0.07
Analysis:
By looking at the results, we can see that as the concentration
of the enzyme increased, the reaction rate decreased. 1/Time
also increased, as the concentration of the enzyme increased.
As I have said already, different enzymes work better in
different conditions. Trypsin, the enzyme we used, works best
in alkali solutions, while amylase and pepsin (other enzymes),
work better in acidic solutions. As we added alkali buffer
solutions the the milk, the time it took for the solution to go
transparent decreased. With highly acidic buffer solutions (i.e.
pH 3 and 5) we did not see any reaction occur. However, the
reaction rate did drop when it was too alkali. After it has
reached its optimum conditions, if even more alkali is added,
the time taken for the solution to go transparent will gradually
increase, as it is no longer at its optimum pH. By looking at my
results, we can see that its optimum pH level was around pH 9.
As I said before, the reaction rates depend on the concentrations
of the enzyme and substrate. If there is a higher concentration of
enzyme, this means that there is more enzyme to react with, which
due to the proportions, will speed up the reactions. From this, we
can say that as the concentration of enzyme increases, 1/Time
decreases.
Evaluation:
Overall, I am very pleased with my results, as they generally
proved my predictions to be correct.
I predicted that trypsin would work best in an alkali solution
and I was correct, as we found out that trypsin's optimum pH
level was 9, (anything above pH 7 is alkali).
If you look at the graph, you can see the reaction rates correlate
very well with the concentration of the enzyme, as the rate
increases steadily, which proves to us that as the concentration
increases, the enzyme works on a greater amount of casein. My
prediction is proven to be correct by this graph.
To improve my experiment, I could have used a wider range of
pHs, and a greater number of different concentrations. Also, if
I had had enough time, I would have seen how long it took for the
solutions with low pHs to go transparent.
Overall, I am very pleased with my results, as they have proved all
of my predictions to be correct, and I did not experience any flaws
in my experiment.
