The experiment:
You keep the same amount of rennin (1cm³) and milk (2cm³) for a fair test. You change the temperature of the water, to see what temperature the enzymes work best at for instance at first the temperature is 30 ºC but each time you do the next experiment you add on 5 ºC. Change the test tubes, so there is no rennin left from the previous experiment.
We have to measure the amount of rennin, water and milk to make sure it is accurate. We will be timing how long it takes for the rennin to react with the milk. We will time it using a stop watch. We will record all the measurements taken.
Prediction:
I predict that the reaction will be faster when the temperature is at body temperature which is probably between 40ºC-45ºC. The reaction will be quiet slow or there will be no reaction if the temperature is either too high or too low.
I predict this because enzymes are in 3D shapes. If you increase the temperature of a chemical you are transferring energy to it, this energy gives Kinetic energy to the particles. When given energy the particles move and collide more often. This is called the lock and key (because the enzyme and the substrate fit into each other) which is also known as the Enzyme substrate complex. Therefore the more kinetic energy given to the particles the more they collide, which results to Active site, this is when the reaction happens. But enzymes are usually damaged at temperatures above 45 ºC, due to a high temperature they change shape because they are Proteins and it has weak molecular bonds, so when you heat them you damage them. Therefore they then tend to denature which results to no reaction whatsoever.
Safety measures:
- Make sure to wear goggles.
- Make sure the rennin and milk don’t mix before the experiment takes place.
- To use tongs to hold hot apparatus or other scientific equipments.
- Tidy the table before the experiment.
- Tuck in stools.
- Stand while doing the experiment.
- Tie hair back.
- To turn gas of when unattended.
- Use the safety flame when not doing the experiment.
Analysis and Conclusion
I noticed as the temperature of the milk and rennin increased, the reaction took less time to take place. At 30ºC the reaction took a long time to take place as it took 1 minute and 24 seconds, then at 35 ºC it took less time approximately 39.5 seconds, at 40 ºC it took 36.5 seconds, at 45 ºC it took 28 seconds and at 50 ºC it took 26.5 seconds. When the temperature reached to 55 ºC the enzymes in the rennin denatured. On my results, at 50 ºC the reaction was at is fastest peak.
The reaction takes place faster as the temperature is at body temperature or when it’s near body temperature, which is approximately 37 ºC according to my results.
When the temperature was at 30 ºC it was too low for the reaction to take place, as there was no heat energy passed on to the particles, which didn’t give the particles any kinetic energy for them to move about. But as the temperature gradually increased to body temperature and round about near the body temperature, more heat energy was given to the particles and they collided more often. This resulted to the enzyme and the substrate to fit into each other. When the temperature was above 55 ºC the enzyme changed shape and denatured.
My prediction matched my results because as I said in my prediction that the reaction will be faster and will work best at body temperature. I also said that the enzymes will denature if the temperatures are too high because of the enzymes changing shapes at very high temperatures.
Evaluation of the Experiment
My method was good because we started from a high temperature to a low temperature so when we wanted the water to cool down we added cold water to it instead of waiting. This saved a lot of time.
My method was also very good because when I repeated the experiment I got similar results.
I could improve my method:
- By using a thermostat, this heated up water ore accurately and saves time instead of heating the water up each time.
- By using a measuring cylinder to measure the miniscus.
- By using a graduated pipette.
- By knowing when the reaction began and ended as it varied each time.
To get further evidence we could:
- Get some one else’s results and compare.
- Use the water bath to make smaller gaps between temperatures to find out the exact point the enzymes denature.
- Do the experiment again. I could improve my investigation by adding acid to the milk and then doing the experiment because Rennin is found in the stomach of young mammals, there is also acid with rennin in the stomach.
- Doing the experiment again but this time using different types of milk for instance: skimmed, semi-skimmed, organic and etc.
I think that my results that were obtained were reliable enough to support my conclusion, as my prediction matched my results. The only problem I had was to know when the reaction ended this could be because of the milk clotting too much for me to realise. The odd results that I got were that the rennin and milk still reacted to each other at 50 ºC on my results, but at 50 ºC the enzymes are meant to denature as that’s above body temperature. This may be because of the rennin not denaturing at 50 ºC.
Afsheen Mahomed 11KAI
Mr White