Prediction:
Enzymes are biological catalysts, they speed up the chemical reactions that happen in living things. Enzymes carry out their at an extremely efficient rate. Enzymes are formed inside cells and after they are formed they leave their cells to carry out their outside. Enzymes that act on lipids are called lipases.
The picture below shows simply how enzymes work. Molecules are continuously around and therefore they bump into each other. When a substrate molecule bumps into the corresponding enzyme, it fits neatly into a on the enzyme, this is called the active site. The reaction takes place here and then the molecule leaves, leaving the enzyme for another substrate molecule.
Active sites of enzymes have a particular shape and because of this only one substrate molecule will fit into it. When an enzyme has lost its shape because of heat, the shape of the active site changes so a substrate molecule will no longer fit. Changing the pH has a similar effect. So the more fat in the milk the faster it will take to turn white because if there is more acid present then the pH falls turning the milk white.
I predict that the higher the fat concentration, the less the whole process will take. This is because when there is more fat each fat molecule will be able to find an enzyme faster so then the enzyme can break it down into fatty acids and glycerol. After the enzymes are completely saturated so more fats can be broken down. This is why the graph levels out.
Prediction graph:
Information from Nelson Biology and Biology for you.
Fair test:
In order for my test many things must keep constant.
-Room temp 22 °C : must keep constant because as little as a 10°C rise in temperature can half the it takes the enzymes to break down the fats.
-Lipase %: A higher lipase concentration will obviously speed up the it takes to break down the fat.
-Amount of milk.
-To stir each milk as lipase is not that soluble in and does settle out.
-Use the same timepiece for each milk.
Table of results:
As you can see the lower the fat concentration as in skimmed milk takes longer to turn white than the higher fat concentrations like whipping cream.
Conclusion:
My procedure went quite well though many things made it hard for me to know if my results are 100% accurate. It would have been hard to maintain a constant room temperature. What I could have done is to keep my different fat concentrations in baths that can maintain a constant temperature. I knew timing was going to be a problem and for this reason I did the experiment three times and took an average. Other similar experiments that I could have done to find out about lipase are changing the temperature and changing the lipase concentration. Because I only had 1 hour lessons in which to do the experiment using milks with less fat took longer, I could have got over this by using milks with higher fat concentrations or raising the temperature to around 40°C. p
