Method
- Shred by using potato grater. This will break open the cells and release the enzymes catalase.
- Put the potato into a boiling tube attached to a delivery tube to allow gas to escape.
- Place the boiling tube into a water bath set it to 30° C and keep it here for 5 minutes so that the cell enzymes heat up to this temperature
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Measure 5 cm3 of hydrogen peroxide into a syringe. Place this into a hole into the bung of the boiling tube.
- Repeat all above steps each time putting the boiling tube into different temperatures.
I will use following rage of temperatures.
24° C, 40° C, 60° C, 80° C and 0° C
- I will use a thermometer to measure the temperature and note in a results chart.
- I will repeat each example once for accuracy
- I will also improve my results with those of my teacher’s.
Diagram
Apparatus
- Stop clock
- Crushed ice
- Electric weight balance
- Grater
- White tile
- Tweezers
- Beehive
- Water bath set to correct temperature
- Clean cloth
- Potato 5gms each experiment plus 25gms for the repeat experiment will equal 50gms
- Hydrogen peroxide 50 ml (5 ml for each experiment) which equal 50 ml
- Conical boiling tube and delivery tube
- Glass tank
- Thermometer
Fair Test
The factor that I will change is the temperature (the aim of my experiment is to find whether temperatures affect the rate of action of catalase)
The factors I will keep the same will are:
- The mass of potato ( 5 gm in each case)
- The volume of hydrogen peroxide ( 5 ml in each case)
- Concentration of hydrogen peroxide
- Source of potato will be the same or the test would be unfair.
How does the enzyme work?
Thousands of chemical reactions take place in living cells to keep them alive. Enzymes make these reactions happen much faster. Chemicals which speed up reactions are called catalysts, and since enzymes work in living cells, they are called biological catalysts.
Enzymes work on substances called substrates. The substrates attach to the active site of same shape and thus a reaction takes place.
All enzymes have some important properties:
- They are all proteins. Hence they have a specific shape.
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Specific enzyme controls one particular reactions (it is specific)
- They can be used over and over again. Hence they are economically viable.
- They are affected by changes in temperature, and each will have its own optimum temperature.
- They are affected by changes pH (how acidic or alkaline) and each will have its optimum pH.
- They can be destroyed (denatured) by heating (boiling).
Enzymes can be used over and over again because, once the products leave the active site, another substrate can fit into the active site hence a reaction can take place. Enzyme keeps on working till all the substrate is used up.
Prediction
My investigation is to find out if the temperatures affect how enzyme (catalase) works upon hydrogen peroxide (the substrate).
I predict that catalase will work differently at each temperature within my range.
At 0° C: at this temperature the catalase will work, but reaction will be very slow since there is little heat energy available for reactants to operate therefore not much oxygen will be produced.
At 24° C: at this temperature reaction will be a bit quicker therefore more oxygen will be produced at this temperature.
At 40° C: at this temperature catalase is very close to body temperature (37° C). I think that the most oxygen will be produced
At 60° C: at this temperature enzyme will slowly start getting denatured but there will still be oxygen produced since not all the enzyme molecules will be denatures.
At 80° C: at this temperature enzyme will eventually denatured, and not much oxygen will produced. Least amount of oxygen will be produced at this temperature compared to the temperatures in the range.
Results
Evaluation
- There were few areas where the methods may not have been followed precisely
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When I took out the syringe from the bung I may have left it open and I may have let oxygen escape from the hole without measuring. This would reduce the amount of O2 in the measuring cylinder.
- Some of the grated potato produced quite a lot of foam which rose in the delivery tube with the oxygen. This made it difficult to read the volume of oxygen in the measuring cylinder.
- My delivery tube was made with 2 parts joining them with a rubber tube. During some experiments this came apart and might have affected my experiment.
- In my experiment there were some results (anomalies result(s) highlighted with black colour )
This is out of line with my prediction. I expected the volume of oxygen to be the greatest at the range of about 40° C and lower at the cold and hot temperatures. It was but 30 ml of 02 is quite high.
How ever my average results followed same pattern as my teacher’s result, and so safely I can say that my results match with my predictions