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How Substrate Concentration Affects a Catalase Enzyme Reaction

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Submitted By bluebird99
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Biology HL
20/9/2013
How Substrate Concentration affects a Catalase Enzyme Reaction
RQ
How does changing the substrate concentration affect the rate of a catalase reaction in an enzyme? Hydrogen peroxide was used as the substrate and the rate was measured by oxygen production.
Hypothesis
If the substrate concentration is increased then the rate of a catalase reaction will also increase until it reaches the optimal concentration or saturation point and will remain constant. This is because there will be more substrate molecules in a higher concentration therefore a higher frequency of collisions. This increases enzyme activity and more product will be formed. However at a certain concentration the enzymes will become saturated (all active sites are full), so an increase in substrate molecules will stop affecting the rate.
Variables
Independent Variable - Hydrogen peroxide concentration
Dependent Variable – rate of catalase reaction by measuring the volume of oxygen produced after five minutes
Controlled Variables – performed at room temperature (21 Celsius), catalase used (potato), weight of potato (1g) in each trial, time given for reaction to take place (5 minutes), method & apparatus
Apparatus
1. Safety goggles & apron
2. Measuring cylinder, 100 cm3 (+/- 0.5cm3)
3. Large plastic tub
4. Access to sink/water
5. Clamp stand, boss and clamp
6. Rubber bung and delivery tube
7. 9 large test tubes
8. Stopwatch (+/- 0.01s)
9. Hydrogen Peroxide, range of concentration: 1%, 3%, 6%
10. Potatoes
11. Cutting board & knife
12. Test tube stands
13. Balance (+/- 0.01g)
14. 10 cm3 Glass pipette (+/- 0.08cm3)
15. Quick release pipette filler
Method
1. Fill the plastic tub 3/4 full (about 3 liters) and place next to clamp stand as shown in figure 1
2. Submerge the 100cm3 measuring cylinder in water horizontally so that it fills with water, tilt opening slightly up so all the air is let out
3. Place the delivery tube in the opening and leave the bung outside the basin
4. Secure the base of the cylinder to the clamp stand out of the water where the measurement indications can be seen, make sure the opening (and delivery tube inside) are deep in the water so that there is no risk of the water falling out during the experiment, refer to figure 1
5. Set the scale and using the knife and cutting board cut nine pieces out of the potato which each weigh 1g. Be as accurate as possible and use the same kind of potatoes. Place each piece in a separate clean and dry test tube
6. Label three test tubes 1%, three 3%, and three 6% and place in stand
7. Use the pipette to measure out 3cm3 of 1% concentrated hydrogen peroxide
8. Release the hydrogen peroxide into first labeled test tube and immediately place the bung on top and start the stopwatch simultaneously
9. Ensure that the experiment area stays at constant room temperature by not performing it near a radiator or opening windows
10. If oxygen isn't being produced shake the test tube and/or delivery tube but be careful to not break the equipment or let the delivery tube fall out of the measuring cylinder
11. After five minutes measure the amount of oxygen produced by the reaction by reading the bottom of the curve of the meniscus at eye level
12. Rinse out test tube in a sink and put away
13. Repeat steps 2-12 for each trial and level of the independent variable by changing or repeating the hydrogen peroxide concentration used in step 7

Data Collection and Processing
Data Collection Table

Volume of Oxygen produced after five minutes (+/- 0.5cm3)
Hydrogen Peroxide Concentration (+/- 0.5%) Trial 1 Rate of Reaction (+/- 0.1 cm3/minute) Trial 2 Rate of Reaction (+/- 0.1 cm3/minute) Trial 3 Rate of Reaction (+/- 0.1 cm3/minute)
1 3 0.6 2 0.4 2 0.4
2 5 1 7 1.4 8 1.6
3 11 2.2 10 2 11.5 2.3
Time for each reaction was five minutes (+/- 5 seconds)
Hydrogen Peroxide Concentration
(+/-0.5%) Rate of Reaction (+/- 0.1 cm3/minute) Range
(+/- 0.1 cm3) Average Rate of Reaction
( +/ 0.1cm3/minute) Standard Deviation
(cm3) Percentage Uncertainty (%) Trial 1 Trial 2 Trial 3
1 0.6 0.4 0.4 0.2 0.47 0.11
3 1 1.4 1.6 0.6 1.33 0.30
6 2.2 2 2.3 0.3 2.17 0.15

Average Rate of reaction
(Trial 1 rate+ Trial 2 rate+ Trial 3 rate)/3 = average rate eg. (0.6 + 0.4 + 0.4)/3 = 0.47

Range of the Rates
Maximum value – minimum value = range eg. Rate of Reaction
Volume of oxygen produced/time (5 minutes) = R.O.R
e.g.

Standard Deviation – Calculate using Microsoft excel

Percentage Uncertainty
(half the range/rate of reaction value) x 100
e.g.

Data Processing

Conclusion and Evaluation My graph shows there is an almost perfect positive correlation between the hydrogen peroxide concentration and the rate of the catalase enzyme reaction, with a correlation coefficient of 0.99. The rate of reaction at 1% concentration was 0.46cm3 oxygen produced per minute and the lowest recorded rate. For 3% was 1.33cm3 per minute, and for 6% was 2.17cm3 per minute and was the highest recorded rate. The rate of reaction at 6% was about 5x greater than the rate of reaction at 1%. The shape of the graph is a constant increase, which disagrees with my hypothesis in which I stated that “If the substrate concentration is increased then the rate of a catalase reaction will also increase until it reaches the optimal concentration or saturation point and will remain constant”. My results support the first half of my hypothesis, however I predicted eventually the graph would plateau due to optimal concentration, which didn’t occur in my results. This may be due to the lack of variety in the levels of IV, possibly the saturation point was at a higher concentration which was not reached or was already reached at 5% but data wasn’t collected to show this. The ideal trend is shown to the right. The catalase is an enzyme which catalyzes hydrogen peroxides breakdown into water and oxygen gas in a “decomposition reaction” by breaking the peroxides bonds. The rate of reaction increases at first because the higher the concentration the more substrate molecules present therefore a higher frequency of collisions. Resulting in more enzyme activity and product formed (oxygen and water released). This was proven in my results, however at a certain point the enzymes will become saturated so all their active sites are filled and the rate is no longer affected, as represented above. There was no evidence of this in my experiment. A student from another class also investigated substrate concentration and her results also didn’t plateau and her graph represented my trend. She did however test with more varied levels of IV but did not go above 6% concentration so one can assume that the optimal concentration is higher. This means our experiment was accurate just we should have tested further. A follow up experiment would be to test a bigger variety of concentrations including higher ones until this optimal concentration is reached. To investigate further I could change my independent variable to temperature of the reaction, investigate the concentration of enzymes, or the effect of pH. When we tested 6% concentration our percentage uncertainty was 7% meaning the method used during those trials was relatively reliable and the results are relatively precise. Whereas the trials done for 1% and 3% concentration both had a percentage uncertainty of 22% meaning they aren’t very precise.
Evaluation
Error Significance Improvement
We did not weigh the potato with high precision, each piece was +/- 0.5g low Use a different form of catalase, like the liquidated liver which can be easily measured precisely using a pipette
There was small variance in our levels of IV high Investigate further also using 2%, 4%, and 5%. Also if higher concentrations can be available to attempt to reach optimal concentration of the catalase enzyme
The delivery tube and bung were constantly falling out of the tube and oxygen produced was lost which affected both the accuracy and precision low Stick the delivery tube further up the measuring cylinder and tape the bung onto the tube during the experiment
The delivery tube was at a downward angle delaying the release of oxygen into the tube high Use a shallower basin and a longer measuring cylinder so that the tube can be at a vertical angle
The was about a 5 second delay in our time measurement due to a slow reaction time which made the results less precise low Use a timer/alarm rather than a stop watch so that when the time goes off is controlled mechanically
The test tube was not shaken consistently for each trial throughout the five minutes making the experiment less precise low Have one of the students shake the test tube constantly for the five minutes
There were not enough/many trials for each level of IV which made our experiment less reliable high Repeat the levels of IV atleast 5 times each

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