Investigation to see how changing the temperature of Milk changes the speed of it’s coagulation after adding the enzyme rennin.


I will be investigating what happens to the rate of milk coagulating when I alter the temperature.



I predict that as the temperature increases, so does the rate of reaction. This is because heat energy causes more collisions between the particles in the enzyme and particles in the substrate. However, very high temperatures damage enzymes by denaturing them.


An enzyme, we are using extra cellular enzymes which control reactions that occur outside cells (for example, digestive enzymes work outside cells in the gut), molecule is globular and very large but only a small part of it, the active site, is involved in the reaction. This Diagram shows how the shape of the active site matches that of the substrate molecule.


The substrate molecule fits into the active site and is held there until the reaction is complete.


The product is then released and the enzyme is once again ready to take part in the reaction. This is known as the lock and key hypothesis. The active site has a distinct shape, rather like a lock. Just as only the right 'key' will fit a lock, so only the right substrate has the right shape to fit into the active site.


Firstly I will measure out the correct volume of milk, this will be 2ml throughout, into a pipette and drop it into the test tube; I will then measure out ˝ml of rennin and drop that into the test tube. I place a bung in the end of the test tube and ask a friend to start the stop watch as soon as I have shaken it once, because the reaction then starts, and placed the test tube into the correct water bath. I will stop timing when the solution turns into a thick lumpy mixture.


I will keep the experiment fair by: -


· Using a different pipette for the rennin and milk so that none get contaminated.


· Only changing the temperature.


· Using the same volume of milk and rennin every time as more will make it a different experiment.


· Repeating the experiment three times to avoid any anomalous results.


Some of the factors that will affect my investigation are temperature of Rennin, temperature of Milk, concentration of Rennin, concentration of Milk, volume of Rennin and volume of Milk.


Temperature of Rennin – this will affect my experiment by giving the Rennin particles more kinetic energy, meaning they will move faster, resulting in a higher number of successful collisions. I will control this by putting my Rennin solution in a water bath that is at 40°C. But if it was too high the experiment would be useless as they would have denatured


Temperature of Milk – this will affect my experiment by giving the Milk particles more kinetic energy, meaning they will move faster, resulting in a higher number of successful collisions. I will control this by putting my Milk solution in a water bath that is at the correct temperature. Combining this with Rennin at 40°C will ensure a fair test.


Concentration of Rennin – this will affect my experiment by giving the Milk particles more Rennin to react with meaning they will have more successful collisions. I will control this by not changing it so that it remains at 5%.


Volume of Rennin – this will affect my experiment by giving the Milk particles physically more Rennin to react with meaning they will have more successful collisions. I will control this by not changing it so that it remains at ˝ml.


Volume of Milk – this will affect my experiment by giving the Rennin particles physically more Milk to react with meaning they will have more successful collisions. I will control this by not changing it so that it remains at 2ml.


I will use the following equipment: -


· Stopwatch – to time the experiment.


· Test tube – to contain the reactants.


· Measuring Cylinder – to measure out the reactants.


I have done a pre-test, the results were: -


40°C


20°C


Time


35 Seconds


124 Seconds


I used 2 ml of Milk, 2ml of Rennin. From this experiment I conclude that the experiment will not take very long and I will use higher volumes of both solutions.


Results






Conclusion


After doing the experiment I conclude that the optimum temperature for the