What are enzymes:
Enzymes are large soluble proteins molecules. We call them biological catalysts, because all living this rely on them. Each chemical reaction that takes place in a human body is catalysed by a specific enzyme.
E.g. an enzyme in your saliva called amylase starts off the break down of starch in your food.
Most reactions speed up as the temperature rises. However when an enzyme gets to hot, it looses its shape and stops working. This is when the enzyme has denatured.
The extra energy at temperatures of 45°C and above make the enzyme vibrate more rapidly, the shaking breaks some of the week bonds holding it in shape. Now the reactant the substrate no longer fits into the active site. And the reaction id not catalysed.
How enzymes work:
Enzymes lower the activation energy of a reaction that is the energy needed to make the reaction take place.
Enzyme + Substrate Enzyme substrate Enzyme +Products
Catalysts is a molecule which speeds up a chemical reaction, but remains unchanged, it dose not take part in the actual reaction. Virtually every metabolic reaction which takes place within every living organism is called catalysed by an enzyme. Many enzyme name end is “ase” i.e. amylase or lipase.
Each enzyme has its own individual shape therefore usually acting on one type of substrate molecule. The enzyme is said to be specific for the substrate.
When the reaction is complete the products leave the site leaving then enzyme unchanged and free to receive and substrate molecule.
Method:
- Place 200cm ³ of water into a beaker and warm up to 20ºC.
- Label two test tubes A and B,
- Using a syringe place 5cm³ starch solution into test tube A
- Using a syringe place 1cm³ amylase solution into test tube B
- Place test tube A and B into a beaker of water (water bath) to warm up to 20ºC
- Wait for two minuets keeping the water bath constantly at 20ºC, whilst you are waiting, set up a dimple tile with a drop of iodine in each dimple.
- Now that the two minuets have passed and both test tubes have been warmed up to the same temperatures pour the contents of test tube A into test tube B and start the stop clock.
- Shake tube B and put it back into the beaker keeping the water at 20ºC
- Every 15 seconds, test the contents of tube B to see if there is any starch left in the solution. Do this by using a pipette to take a sample from test tube B and dropping it into a new iodine drop in the dimple tile.
- Keep repeating this experiment every 15 seconds until the iodine shows that there is no longer any starch left.
- Repeat this experiment using the same volume of starch and amylase at higher temperatures e.g. 30ºC, 40ºC 50ºC etc
- Repeat each experiment twice to make an average for your results
- Then to prove that is it the amylase that reacts with the starch to break it down, do one of the experiments again taking away the amylase and replacing it with water.
I will record my results in the following results table below.
Apparatus:
2test tubes 10 ml Syringe
250 ml beaker 1ml Syringe
Bunsen burner Pipette
Tripod 2%Amylase solution
Gauze 1% starch solution
Heats proof mat Iodine Solution
Thermometer
Stop clock
Your apparatus should be set up similar to the diagram below.
For the Experiment you will need:
- Stop clock - Amylase Solution
- Pipette - Starch Solution
- Dimple tray - Iodine solution
- Heat proof mat - Gauze
- Beakers - 2 test tubes
- Thermometer - Tripod
-Bunsen Burners
Safety:
The safety aspects fro this investigation it’s very similar to other experiments which include boiling.
Goggles are needed so that none of the chemicals used can be splashed into your eyes and damage them.
Hair needs to be tied up so that it dose not catch on fire.
Gloves/Tongs hot equipments needs to be handled with care and to be protect yourself from getting burnt.
Bunsen burner should not be used on a blue flame when not in use.
Chemicals should be used with care; any spilt chemicals should be cleaned away in the most appropriate way. (Iodine X )
Loose clothes, need to be taken of before the experiment is taken place.
Fair test:
To make it a fair test:
- Ensure that exactly 200cm³ of water is in the water bath each time the experiment is done.
- Make sure that the temperature stays at 20ºC, and is constant for each individual experiment.
- Make sure that 1cm³ of amylase is in tube B.
- Exactly 5cm³ of starch solution is used in test tube A
- Start the stop clock as soon as test tube A is mixed with test tube B.
- Before the solution of A and B are placed back into the water bath shake well.
- To take samples of the solution every 15 seconds.
- When the experiment is repeated make sure that the same procedure is taken place.
Repeat experiment at different times
20ºC 30ºC 40ºC 50ºC 60ºC 70ºC
Prediction:
My prediction for the optimum temperature that amylase will digest starch will be body temperature which is approximately 37ºC-40ºC This is because body temperature is 37ºc. When the amylase is breaking down starch it is broken down in the mouth and the small intestine. The body temperature is approximately 37ºc in both of these places. We need amylase to break down starch so that our body has enough energy for us to be active.
So the optimum temperature that I predict will be between 37ºC and 40ºC because we need our energy as fast as we can.
As the temperature increases the molecules gain more energy and move around much more, therefore there is likely to be much more of a successful collision. Between the enzymes amylase and the substrate starch. When the temperature gets to high at approximately 60ºC the enzyme becomes denatured and the substrate can no longer fit into the active site. The reaction then slows down and is no long efficient.
I also predicted that, with time, the starch concentration would decrease for each temperature tested. As the starch concentration decreases the enzyme finds it more and more difficult to find enough substrate to act upon.
Results:
My results table
From my table of results I have come to the conclusion that the optimum temperature at which amylase is 40ºC. This is what I had predicted.
Obtaining my evidence:
Throughout the whole experiment I did not change anything that I wrote in my method I used the exact amount of starch and amylase . I did not change the amount of water I used. I used the right equipment with as much accuracy and proficiency that we could do. Obviously we could of done the experiment with more proficiency if we had done it in a professional laboratory, this is why the results varied
Preliminary:
Most of my ideas and prediction for this experiment came from two past experiments done in class.
- Being the effect oh pH on amylase activity
- The action of lipase on milk fats
pH Amylase activity
In the previous experiment I was trying to identify the optimum Ph that amylase would digest starch quickest at. We found out that the optimum temperature was pH 9, now this was expected as this is the average pH that is found inside humans. This means that more alkaline conditions are needed for amylase to digest starch.
Lipase on milk fats
In this preliminary experiment. I was trying to identify the optimum temperature at which lipase would digest milk fats fastest at. The optimum temperature for this was 45ºC. This means that the temperature needed to digest milk fastest by lipase successfully is 45ºC.
The effect of pH on amylase activity
The action of lipase on milk fats
This graph shows the results that I got from my first experiment.
From looking at the graph and putting in my line of best fit I would say that 60°c is the optimum temperature. To make sure that it is 60°c I should have done the temperature 80°c to make sure there was a rise in the time and that 60°c is the optimum temperature.
Most of the points do go through the line of bets fit and it shows that the there is a pattern. The only point on the graph that could have been wrong was at 40°c. this is very far away from the line of best fit.
This graph shows the times that I got from the second experiment that I did.
This graph is not very accurate and most of the points are not in the right place. It still shows that 60°c is the optimum temperature but it not very reassuring.
To be absolutely certain that 60°c is the optimum temperature then I should have carried on to 80°c like in the first experiment.
At 20°c the time was very high and it took very long for the amylase to digest the starch. At 30°c there is a big drop and then the time rises again at 40°c which is why the results and very accurate. If I had tested at 80°c the time could have come down again. I would have to see a strong rise in the line of best fit for there to be enough evidence to say that 60°c is the optimum temperature.
In this graph it shows all the average times from both experiments.
From this graph I have the information that 40°c is the optimum temperature. I am very confident that it is 40°c because from both experiments it has been 40°c that has been the optimum temperature. On the second experiment I wasn’t very clear but on the rest of the experiments it was. On the first experiment that I did, it showed very clearly that 40°c was the optimum temperature.
On the first experiment the line of best fit was very good and showed a clear pattern in what was happening when raising the temperature.
Drawing Conclusion
The results were as I predicted in my prediction. In my prediction I said that 30°c - 40°c would be the optimum temperature because the amylase would work best at body temperature.
Evaluation
I have found out that 40°c is the optimum temperature for amylase to digest starch.
If I were to do this experiment again I would use a colorimeter because it would be more efficient and would tell me exactly how much starch was in the iodine solution. I would also expand the range of temperatures that I would use. I only went up 70°c in this experiment because I thought the optimum temperature was quite low. I was right in my prediction.
