Apparatus
- Test tubes
- Milk (different fat concentrations)
- Sodium carbonate
- Lipase (5% conc.)
- Phenothalin
- Test tube rack
- Stop watch
Prediction
I think that the lower the substrate concentration the faster the reaction will be. This is because there is less fat for the lipase to work on and therefore it will take less time.
Variables
- Amount of milk – 5 cm³
- Amount of sodium Carbonate – 7 cm³
- Amount of lipase – 1 cm³
- Heat – room temperature
Results
Analysis
The results and the graph clearly show that as the substrate concentration increases the time decreases. Therefore this has proved my prediction to be wrong. I predicted that as the substrate concentration increased then so would the time, because at the time I believed that the more fat particles there was the longer the reaction time would be. But my experiment has proved my wrong, and it has made clear that the more fat particles there are the quicker the rate of reaction. This is because there are more fat particles for the lipase to react with and therefore more chance of a collision between the two so more chances of reaction and so the reaction is faster. And like in the skimmed where there are far fewer fat particles than in other milks there is less chance of a collision and so the rate of reaction is slower.
The skimmed milk doesn’t have a time because it was taking far too long to react and so it was decided to end the experiment so we could go onto the next one, but there wasn’t enough time for the reaction to take place. This is because (as I explained before) there are very few particles of fat in the skimmed milk and so therefore there is less chance of collision between the fat and the lipase and therefore the reaction takes much longer.
The results of the experiment are good, even though I would like to have a result for the skimmed milk it would take a very long time to react and so would be off the graph anyway and would make no difference to how it is now. There were no problems with the rest of the experiment though and the results show that the experiment went well.
If I could do this experiment again I would take more time over it and I would like to see how long it would actually take for the skimmed milk to react. But I could try to speed this up by using bile salts in all of the different types of milk, as bile salts break down the fat particles into smaller pieces and therefore make it easier for the lipase to digest, I am aware that there are not many fat particles in the skimmed milk anyway but if the bile salts could brake down whatever there already is then there would be more particles for the lipase to react with. Of course the bile salts would have to be added to all of the test tubes and so they would all react much quicker as well. But that is not a problem, as it would just speed up the time the experiment takes and therefore save time in the end.
