Before beginning the investigation on the digestion of fat by lipase I first carried out a preliminary experiment to discover how much Sodium Carbonate should be used- this is valid to the experiment because the amount of Sodium Carbonate will affect the amount of time taken. A shorter time would be more beneficial, to enable me to check results.
Method:
1. Place the following into a test tube:
3cm Milk,
1cm Lipase.
3 drops phenolphalein.
2cm Sodium Carbonate.
2. Place test tube into a water bath at 38
3. Using the stopwatch time how long it takes for the colour to change from pink to colourless.
4. Repeat steps 1-3 for 3cm and 4cm Sodium Carbonate.
Results:
These results show that is best to use 2cm Sodium Carbonate for this experiment. It took a short amount of time for the 2cm amount because this meant that there was less alkaline mixture to turn acidic.
The phenolphthalein turns colourless due to the production of acid throughout this experiment.
Fat ---------→ fatty acids + Glycerol.
The aim of this experiment is to discover the effect of temperature on the digestion of fat by lipase.
The Independent variable in this investigation is temperature the other factors will remain the same to see what effect the temperature will have on the dependent variable digestion.
I will test the digestion of fat in the following temperatures:
20 ,30 , 40 , 50 , 60 ,this is because the range covers the optimum temperature of an enzyme’s rate of reaction and also allows it to experience high temperatures.
Method:
- Place in a test tube.
3cm milk
1cm lipase
3drops phenolphalein
2cm Sodium carbonate
- Place the test tube in a water bath at room 20 .
- Using a stopwatch time how long it takes for the colour to change from pink to colourless.
- Repeat steps 1-3 for water baths- 30 , 40 , 50 ,60 .
Diagram:
Prediction:
I believe that the enzymes will work best at a temperature of around 40 this is because when enzymes are exposed to high temperatures it causes the molecules within the enzyme to vibrate to rapidly and damage their structure causing denaturation and deactivation of the active site.
I have also required the knowledge to know that enzymes work very efficiently within the body and therefore I believe that they will work just as well outside of the body at around the same temperature. Another factor, which adds me to believe this hypothesis, is the preliminary experiment I carried out- the experiment containing the 2cm of Sodium Carbonate at 38 also took the shortest amount of time.
As enzymes exist within cells where the pH is 7 the most favourable pH is obviously 7- a pH of significantly higher or lower than 7 will also damage/denature the cells.
Results:
Conclusion.
The results above do not show the relationship between digestion of fat by lipase and temperature to that I would have hoped. The table of results show that the fastest reaction in this experiment was 60 These results do not confirm my prediction that enzymes would work best at around body temperature. However as the enzymes haven’t been denatured it shows that the enzymes must have been more heat stable- this can depend on a number of things- for example how old the enzymes are.
Evaluation.
I believe that I worked well throughout this experiment and although my results did not follow my prediction that they are a “one off” dependent on the nature of the enzyme.
I think this experiment could have been improved by using a computer to time the experiment and use a computerised thermometer to check the temperature of the water baths to more accuracy.
You could test this experiment for another type of food e.g. sugar using benedict’s solution at different temperatures to see if the enzyme followed the same pattern or followed my prediction.
