- Concentration of substrate.
- Concentration of enzyme.
- Volume of substrate.
- Volume of enzyme.
- Temperature of substrate previous to being added to enzyme.
- pH of enzyme.
- pH of substrate.
- Temperature of enzyme.
- Temperature of substrate.
An experiment to investigate how enzyme concentration affects an enzyme controlled reaction using catalase and hydrogen peroxide (following original method)
Apparatus
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A 1000cm3 beaker
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A 25 cm3 measuring cylinder
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A test tube
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A bung
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A 10cm3 syringe
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A delivery tube
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A stopclock
- 5 mixing pots
Method
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Take 3cm3 of the undiluted enzyme solution and place into a mixing pot-100% concentration (original).
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Take 8cm3 of the enzyme solution and mix with 2cm3 of water in a mixing pot-80% concentration (solution 1).
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Take 5cm3 of solution 1 and mix 5cm3 of water in a mixing pot-40% concentration (solution 2)
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Take 5cm3 of solution 2 and mix 5cm3 of water in a mixing pot-20% concentration (solution 3)
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Take 5cm3 of solution 2 and mix 5cm3 of water in a mixing pot-10% concentration (solution 4)
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Fill a 1000cm3 beaker ¾ full with water. Fill a 25 cm3 measuring cylinder to the brim with water and place your thumb over the top, invert the measuring cylinder taking care to prevent any loss of water and position in the beaker so that the mouth of the cylinder is below the waters surface.
- Take the delivery tube and place one end under the lip of the measuring cylinder.
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Place 3cm3 of the original solution in test tube.
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Place 3cm3 of hydrogen peroxide in a 10cm3 syringe and squirt into the test tube containing the catalase, insert the bung as quickly as possible. Start the stopclock at the same time and measure the amount of gas produced in the measuring cylinder in a 3 minute time period.
- Repeat twice more.
- Repeat this process for each of the following solutions: 80%, 40%, 20%, and 10%.
The independent variable in this experiment is the enzyme concentration; all other possible variables are kept constant to make it a fair test.
The following things will be kept controlled:
- Concentration of substrate.
- Volume of substrate.
- Volume of enzyme.
- Temperature of substrate.
- Temperature of enzyme.
- pH of enzyme.
- pH of substrate
If the enzyme concentration was kept constant, any of the controlled variables in the list above could be varied to produce a different experiment and therefore a different result.
I predict that the higher the enzyme concentration the higher the rate of reaction, this is because there are more enzymes per cm3 to which the substrate can attach and react with therefore more oxygen will produced in three minutes with the undiluted solution-100%.
All results must be recorded in a table and later plotted into an appropriate graph using the averages of the three results at each enzyme concentration as diagrammed below.
A table to show the volume of oxygen released in cm3 at varying enzyme concentration
A graph to show the volume of oxygen released in cm3 at varying enzyme concentration
The main trend of the graph agrees with my prediction and shows. The results were in general quite accurate although there were a few anomalous results- there was an overlap of results between the 80% and 100% concentration at points 1, 2 and 3 this could be due to the concentrations being similar, contaminations during some point of the experiment, variations in room temperature or inaccurate reading of results. There was also an anomalous result at 20% concentration that seemed to be slightly higher than the trend this may have been for similar reasons.
The majority of the results were reliable but the experiment could have been improved in the following ways:
- The bung should remain on the test tube at all times to prevent any gas from escaping and giving an inaccurate result. This involves having a syringe to add the hydrogen peroxide to the solution which has its nozzle inserted through the bung
- To stop the temperature of the solutions from varying too much with the room temperature a waterbath should be used as water stays at a constant temperature most of the time.
- A smaller sized measuring cylinder could be used as this allows the amount of oxygen to be read more accurately.
Overleaf is a version of how the experiment should be practised if the experiment was to be repeated in the future.
An accurate experiment to investigate how enzyme concentration affects an enzyme controlled reaction using catalase and hydrogen peroxide
In this method all errors addressed on the previous pages have been corrected and the method has been changed for more accurate results
Apparatus
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A 1000cm3 beaker- this will be large enough for the researcher to fit their hand and measuring cylinder in easily so that no air is allowed into the measuring cylinder in the process.
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A 10 cm3 measuring cylinder- this will give a more accurate reading of the oxygen amount than a larger version.
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A 100 cm3 conical flask and bung- the bung prevents any gas from escaping, the conical flask gives a larger surface area to the catalase so it will heat more quickly.
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A 10cm3 syringe- the syringe will be inserted into the bung; this prevents gas escaping, as the bung will be on while the hydrogen peroxide is added.
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A delivery tube-this also fits into the bung preventing gas leakage and fits under the lip of the measuring cylinder sending the gas to the top.
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A digital thermometer- a digital thermometer is much more accurate than a mercury one as the temperature is displayed on the screen so no mistakes can be made when reading it.
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A digital stopclock- a digital stopclock is easy to use and quick to read therefore making it more accurate than an analogue stopwatch.
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A waterbath- this keeps the catalase at a more constant room temperature so it is less affected by room temperature changes during the course of the experiment.
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5 mixing pots- these contain the enzymes of different concentration and with the lid they help prevent spillage or contamination.
Method
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Take 3cm3 of the undiluted enzyme solution and place into a mixing pot-100% concentration (original).
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Take 8cm3 of the enzyme solution and mix with 2cm3 of water in a mixing pot-80% concentration (solution 1).
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Take 5cm3 of solution 1 and mix 5cm3 of water in a mixing pot-40% concentration (solution 2)
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Take 5cm3 of solution 2 and mix 5cm3 of water in a mixing pot-20% concentration (solution 3)
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Take 5cm3 of solution 2 and mix 5cm3 of water in a mixing pot-10% concentration (solution 4)
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Fill a 1000cm3 beaker ¾ full with water. Fill a 10 cm3 measuring cylinder to the brim with water and place your thumb over the top, invert the measuring cylinder taking care to prevent any loss of water and position in the beaker so that the mouth of the cylinder is below the waters surface.
- Take the delivery tube and place one end under the lip of the measuring cylinder.
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Place 3cm3 of the original solution in a conical flask, place in the waterbath and allow to acclimatise to room temperature for 10 minutes.
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Place 3cm3 of hydrogen peroxide in a 10cm3 syringe and insert through the bung of the conical flask alongside the delivery tube, insert the hydrogen peroxide making sure the bung is tightly on so no gas escapes. Start the stopclock at the same time and measure the amount of gas produced in the measuring cylinder in a 3 minute time period.
- Repeat twice more.
- Repeat this process for each of the following solutions: 80%, 40%, 20%, and 10%.
Below is a diagram of the apparatus layout for this experiment:
Bibliography
AS Guru-
Revise AS Biology-Parker, John-pg 46-51, 26 and 27
Biology pages-http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/E/Enzymes.html
The Biology Project, University of Arizona-http://www.biology.arizona.edu/biochemistry/problem_sets/energy_enzymes_catalysis/01t.html