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HSC Biology
Practical A: Temperature
Substrate: Milk Enzyme: Rennin
Aim: To investigate how different temperatures alter the rate of reaction between milk and an enzyme (rennin) when they are combined.
Hypothesis: The milk and rennin will react the fastest at a temperature of 40oC as this is closest to the optimum range in mammals.
Materials:
∝ Junket tablets (Rennin)
∝ Stop watch
∝ Hotplate for water bath.
∝ Bucket of Ice for 0oC test.
∝ 6 Beakers (one for each temperature)
∝ 10 Test Tubes (one for milk, one for rennin)
∝ Milk
∝ Thermometer
∝ Measuring Cylinder
∝ Mortar and Pestle
Method:
1. Set up the hotplate and water bath by placing two beakers also filled with water inside the bath.
2. Place a thermometer in the water bath and get its temperature to 40oC.
3. Set up the bucket of ice on a bench.
4. Using the measuring cylinder, measure 3mL of milk and transfer it to one test tube.
5. Grind up 1 junket tablet with the mortar and pestle and add 15mL of water to it.
6. Using the dropper, take 3mL of the rennin mixture and place it inside one test tube.
7. Place both test tubes in the water bath and leave them there for 5 minutes.
8. Take both test tubes out & have a stopwatch ready. Add the enzyme to the milk and time how long it takes for the milk to coagulate.
9. Record Results
10. Repeat steps 2-9 with the water bath at room temperature, 60oC and 80oC.
11. Repeat the experiment to get accurate results.
Variables:
Independent Variable The temperature of the water
Dependent Variable The time the milk takes to completely set
Control The amount of milk & rennin.
Results:
Temperature 0oC Room Temperature (250C) 40oC 57oC 82oC
Time Taken (minutes/seconds)
Part A Over 10 minutes 4m 12s 1m 16s 2m 18s Denatured
(no reaction)
Time Taken (minutes/seconds)
Part B Over 10 minutes 4m 56 s 1m 12s 2m 31s Denatured
(no reaction)
Average Time
(minutes/seconds) Over 10 minutes
4m 34 s
1m 14s
2m 24 s
Denatured
(no reaction)
Discussion
The investigation was carried out to investigate the effect that different temperatures had on the rate of reaction between the enzyme rennin and milk. From the results of the practical, it is clear that the fastest reaction took place at 40oC with an average time of 1 minute and 14 seconds. This is due to the fact that 40oC is the closest temperature to the optimum level of 37oC inside that of the human body, as rennin is an enzyme that occurs in the stomach to solidify milk.
The reaction that occurred at 57oC reacted surprisingly fast as although it was 17oC above the optimum temperature, it managed an average time of 2 minutes and 24 seconds. At 0oC the enzyme was not denatured, however it took over 10 minutes to react which would be very ineffective inside the human body. At 82oC the enzyme was denatured, with no reaction taking place due to the effect of the higher temperature.
In relation to the human body, the enzyme rennin can continue to react with milk to temperatures of 60oC down to 00C, with 40oC being the fastest reaction. At 80oC the enzyme was denatured, which is a clear reflection of the functions inside the human body that were modelled inside the lab.
Conclusion
In conclusion, the aim of the practical was answered with relevant results and the hypothesis was confirmed. A variety of temperatures were tested which ranged from 00C up to 800C which gave expected results in relation to how rennin solidifies milk inside the stomach of the human body. Inside humans, the optimum temperature at which enzymes operate is 370C. Therefore is was rightful to assume in the hypothesis that the fastest reaction will occur in the water bath of 40oC, which was confirmed with a reaction time of 1 minute 14 seconds.
By testing several different temperatures in the investigation as mentioned in the aim, it was clear that temperature had a clear effect on the rate of reaction between rennin and milk.
