8. A stopwatch to time how long the reactions take to clear the solution
9. a peace of white paper with crosses on the paper to observe how much solution have cleared
10. used 5cm3 of trysin and 5cm3 of marvel because it doesn’t take a long time to do the experiment and it also gives a clear result
11. water and acid for controls to compare with other solution to see whether the solution are fully reacted or not
12. specimen tubes and lids to shake and to compare with other solution.
A diagram for apparatus
Methods
1. I will collect the data by first of all, put 6 tubes on the crosses of a piece of white paper.
2. I will put 5 cm3 of 4% Marvel milk in all tubes. Since my aim is to find how the different concentration of enzyme affects the rate of reaction therefore we used the same concentration of Marvel to all test tubes to observe their rate of reaction by adding different concentration of enzymes.
3. add 5cm3 water to 5 cm3 of Marvel and 5 cm3 HCl to another marvel tube to compare the colour standard with other solutions to see whether they are fully reacted or not. Because acid completely digests marvel and makes it clear but water doesn’t digest at all.
4. I will add 5 cm3 volumes of 1% trypsin to 5 cm3 volumes of 4% Marvel to make up 10cm3 in total and repeated for the other e.g. 5 cm3 of 7.5% trypsin and 5 cm3 of marvel
this table shows how concentrations are made up
5. I will measure the time it takes for the marvel to completely digest (clear)
6. I will always remind myself to be careful with the experiment since the chemical that we use can be quite dangerous. For example we use HCI for the control(acid), which may cause burns and vapour is very irritating to respiratory system. Also enzymes are all potential allergens which can cause asthma or irritate membranes of the eyes or nose. Therefore I will be wearing goggles and lab coat to prevent it getting into my eyes and skin. And I will wash out my hands quickly if I touch HCI.
I think that my method is accurate enough to give reliable data since it I have considered many things to make the experiment more accurate.
Lastly, I will repeat my experiments 3 times so my results are more accurate. I will repeat any anomalous result to ensure my results are reliable.
Prediction :
Enzymes are biological catalysts which speed up reactions in living organisms, but not get used up during the reaction which are made of globular proteins. The actual area of the enzyme which binds to the substrate is called the active site. The active site of a particular enzyme has a specific shape into which one kind of substrate will fit.
This is Fischer’s ‘LOCK AND KEY’ HYPOTHESIS where substrate is the key which will fit in the enzyme, lock.
Therefore, I predict that, as the concentration of trypsin is increased, the rate of breakdown of casein will increase. In fact the rate of reaction will be directly proportional to the concentration of enzyme. Because as enzyme concentration increases more active sites will become available so the rate of the enzymatic reaction will increase.
Also the more particles there are, the more collisions will occur due to their kinetic energy between enzyme and substrate and therefore the move like that successful reactions will occur. I.e. rate increases.
Therefore, I am led to believe that if you double the enzyme concentration then you will also double the rate of reaction, due to double the amount of collisions by molecules, as long as the substrate concentration is maintained at a high level, other conditions, such as pH and temperature are kept constant.
The rate of an enzyme reaction is measured by the amount of substrate changed or the amount of product formed, during a period of time. If activity is measured over a period of time, I predict that my graph at a point the rate of reaction will level off as numbers of enzyme molecules will outnumber substrate molecules. Therefore, I can say that it has reached ‘ the limiting factor’ where the rate will not increase and there aren’t enough substrates to pair off with the enzymes to produce increasing product.
This is the graph of what I predict for the experiment
Analysis
The graph shows that the rate of reaction increases as the enzyme concentration increases as long as the substrate concentration is maintained at a high level, pH is kept constant and temperature is kept constant as I predicted in my prediction. It is because as enzyme concentration increases more active sites will become available so the rate of the enzymatic reaction will increase. The substrate concentration has to be maintained at a high level, because there should be enough substrate to fit with enzymes otherwise enzymes are useless. Also we have to keep temperature constant since as heat increase molecular motion, thus the reactants move more quickly and chances of their bumping into each other are increased until it reaches to its optimum point where the enzyme starts to denature. And pH has to be kept constant because enzyme is very sensitive to pH so changes of pH cause the enzyme shape to alter so the enzyme would no longer fit into substrates.
I predicted a proportional line. I predicted a linearly proportional line in which if you double the enzyme concentration than you will also double the rate of reaction, due to double the amount of collisions by molecules however, my graph didn’t fallow my prediction. Because, when the concentration of enzyme is 0.25, the rate of reaction is 3.38 however when the concentration of enzyme is 0.5, the rate of reaction is only 4.81. So it does not double. For the other example, when the concentration of enzyme is 0.5 the rate of reaction is 4.81 however when the concentration of enzyme is 1, the rate of reaction is only 7.00. Therefore, my experiment does not double. I believe that there are some errors or mistakes which didn’t allow my rate to be directly proportional to the concentration of enzyme.
Also, I predicted that there comes a point where all the active sites of the enzyme are saturated so the graph will level off, in other words it will meet a plateau since numbers of enzyme molecules will outnumber substrate molecules. However, I could not clearly found the graph leveling off since there was always enough substrates for enzymes to react with. In fact the highest concentration of enzyme was only 1% and marvel was 4%. Therefore my graph didn’t agree with my prediction.
Evaluation
I believe that my result was accurate enough to see that the concentration of enzyme increases as the rate of reaction increases. If you see the result table then you can absorb that the first and second experiments were very close together. However, I can observe some unanimous results which in the third experiment. All the third experiment took far too much more time to clear the marvel compare to the first and the second experiment. In fact the third experiment is about double as the first and second experiment. Therefore, I just accounted average between first and second experiment. And I am led to believe that there must have been some mistakes or errors.
The result table
* = anomalous
in the third experiment, 1% concentration of enzyme took 300s where the average between first and second was only 143s. 0.75 % took 420s where the average between first and second was 172s, the 0.5% took 408s where the average was 208 and 0.25% took 510s to clear marvel in the third experiment where the average was only 261s.
I think that the anomalous result happened firstly because the beakers that I used for the third experiment had different beaker temperature. I did not have enough beakers to do the third experiment therefore, I washed the beakers that I used for my second experiment with cold water to do the third experiment, the beakers temperature must have affect the temperature of enzyme. Furthermore, I opened the windows before I did my third experiment when the temperature outside was very cold and windy, and I did my third experiment on the window sill. I believe these two things affected my experiment. It is because enzymes are very sensitive to temperature therefore as the temperature decrease the rate of reaction also decreases since the coolness decrease molecular motion, thus the reactants move more slowly and chances of their bumping into each other are decrease according to Collision Theory.
The other reason that I can think of are, while I was doing the third experiment, it was really hard to tell if the solution is completely reacted or became clear. Therefore I could have measured time after the marvel is completely digested. Also, I did two experiments already before I did the third experiment so my reaction was not as good as the first and second experiments the reason that I am not a Robert. Therefore I think that I could start timing late which could have affected my experiment.
Lastly, if you see my result table, you can observe that the first experiment takes least time to clear Marvel. I believe that it is because I might was holding the beakers for a longer time in the first experiment which could increase temperature and increase the rate of reaction. Because as the temperature gets high the rate of reaction increase as well since high temperature increase molecular motion, thus the reactants move more quickly and chances of their bumping into each other are increasing according to Collision theory. Also, I should have had more concentration while I was doing the first experiment than the second and the third ones. So I should have started timing much more accurately therefore I should have missed some time of reaction which happened in the third and a bit of in the second experiment.
The third experiment was took too much more time than the first one and the second one. Therefore I didn’t include the third experiment when I calculated the rate of the reaction. As a matter of fact, the graph trend was very similar to what I predicted and gave me a good enough to conclude that as the concentration of enzymes increases then the rate of reaction increases.
Further works
I wanted to see my graph meeting a plateau<leveling off> which I predicted in my prediction. However I could not observe it from my graph since the range of the concentration of enzymes was too narrow. Therefore for my further works I would just repeat the experiment with increased range of the concentration of enzymes which will be 0 ~ 5 percent so that I can hopefully see my graph leveling off and can conclude that I observed my graph levels off at a certain point as numbers of enzyme molecules will outnumber substrate molecules. Therefore, I can say that it has reached ‘ the limiting factor’ where the rate will not increase and there aren’t enough substrates to pair off with the enzymes to produce increasing product.
I would also want to do another experiment to give evidence that enzymes are sensitive to the temperature because I think that my third experiment went wrong mainly because of different temperature.
Method
I would get samples of starch solution and the enzyme amylase (which breaks starch down into simple sugars) are misted together and kept at different temperatures. Samples from each experiment are tested with iodine at regular intervals.
The result and conclusion
In the presence of starch iodine turns blue-black, but when there is no starch present the iodine stays yellowy brown. It is evidence such as this which demonstrates the effect of temperature on the rate of enzyme-controlled reaction.