Pilot Results:
Hypothesis:
Using the ‘lock and key’ theory and the collision theory, I hypothesise that the lager the concentration of Hydrogen Peroxide, the less time it will take the catalase beads to react.
This is the ‘lock and key’ theory, of how enzymes work:
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We can see from above, that the Hydrogen Peroxide molecules have the correct code, and connect on to the catalase enzyme to form an enzyme-substrate complex. The product(s) produced then leave the enzyme. The enzyme is left unchanged, so it can be used again.
Collision Theory:
As the concentration of H2O2 doubles, the amount of H2O2 particles also double. Therefore, if there is double the amount of particles, there is more chance of collisions to happen between the H2O2 and the catalase enzymes. These collisions cause reactions, and so there will be the same amount of reactions in half the time. Thus the more H2O2 there is, the quicker the reaction will take place with Catalase; double the concentration of H2O2 half the time taken to react.
Safety:
- We used Safety Goggles, to make sure we got nothing in our eyes
- Lab coats were put on, so we could protect our clothes and skin.
- We also tucked in all our clothes under the lab coat like our ties or shirts.
- If we made a spillage, we would clean it up immediately and neatly.
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We stood up so we could get away quickly if we had a spillage of H2O2on us.
Variables:
I made sure, that the volume of the H2O2 was added by 2.5 each time, and nearest to line as I could get it. As I stated before, the two conditions that affect the rate of H2O2 breaking down is temperature and concentration. So because we were controlling the concentration, we had to make sure that the temperature was the same throughout the whole experiment. We used a thermometer to overcome this. The dropping height we kept the same too, for the reason that I started the stop clock when I dropped the bead, which I also kept the same too. I made sure that the sizes of the beads were the same sizes. The ones that weren’t, I got rid of.
I expected that the temperature would mainly affect my results above all other variables. This is because the catalase works best at a certain temperature, and so I had to try and keep my beads and concentrations of liquids as constant as I can throughout the whole experiment. I used a thermometer to measure the temperature, to make sure it wasn’t rising in temperature.
Other variables could also influence my results, such as the concentration of light. This was hard to keep constant, but the light intensity from the sun didn’t change within the hour. Furthermore, I could have used some sort of catalyst (like stirring, heating or pressurising), but I though it was unnecessary, as the results I received were satisfactory.
Enzymes:
Enzymes were first discovered by accident by a German chemist called Eduardo Buchner in 1897. An enzyme is generally a protein and an organic compound. They speed up chemical reactions (a catalyst), which naturally occur in living organisms. They each have their own ‘code’, to react with particular substances. They become denatured when the temperature ranges about 5 oC above or below their peak (normally peak is 37 oC), or if the pH becomes too acidic/alkali.
Catalase acts only on hydrogen peroxide, and is one of the fastest enzymes. Hydrogen Peroxide is found in the body as a by-product, and is a toxin; that’s why we need catalase to break it down. Catalase is found in yeast, potatoes and liver cells. Because the enzyme catalase is found in yeast; when the yeast cells are added to the Hydrogen Peroxide, it catalyses the reaction. This is an example of an organic catalyst, which is quicker and more effective than inorganic catalysts. The only disadvantage, is as I have said before, the enzymes can be easily affected by extremes in temperature and pH, which don’t really affect the inorganic catalysts.
Temperature is a very important factor, the higher the temperature the quicker the reaction. So I made sure that the reactions happened at all the same temperature to keep it a fair test. For this I used a thermometer. I had to make sure that all of my beads were more or less the equivalent size. If they were noticeably too big/small, I would discard them.
Apparatus:
- 3ml Yeast
- 3ml Alginate
- 30ml Calcium Chloride solution
- 30cm glass rod
- 25ml measuring cylinder
- Hydrogen Peroxide
- Water
- Stop clock
- Pipettes
- Tweezers
- Test-tube Rack (and 12 test tubes)
- Thermometer
Diagram of Experiment:
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Method 1:
Making the bead, we mixed the yeast and the alginate together with equal proportions. i.e. I used 2ml of yeast, and 2ml of alginate. Once mixed together well with a glass rod, I then took out the rod, placed it about 10cm above a large beaker of Calcium Chloride solution, and the yeast-alginate drops drip into the liquid. When they were solidified, I repeated the process, until I had at least 40 beads. I then discarded the malformed ones.
Method 2:
I used a 25ml-measuring cylinder, to obtain the Hydrogen Peroxide, water and bead. Then I filled the reacting cylinder with the required amount of water and Hydrogen Peroxide to fill 20ml. I then rested the pair of tweezers holding the bead, on the top of the reacting tube. I dropped the bead, and started the stop clock at the same time. I stopped the clock, once the bead had reached the meniscus of the liquid. After recording the time, I then repeated the experiment with the next concentration of Hydrogen Peroxide and water.
Analysis:
Evaluation:
