The effect of Temperature on Enzyme Action (Rennin)

Materials

• Beakers 250ml
• Bunsen burner
• Tripod stand and gauze
• Test tubes
• Rennin solution
• Stopwatch
• Measuring cylinder
• Test tube rack
• Milk
• Thermometer
• Pipette

Method

1. Firstly the students obtained rennin solution which was kept in refrigerator.
2. Then they prepared a water bath at 40°C in a 250ml beaker.
3. After that they placed 5ml of milk into two test tubes labelled A & B and 1 ml of rennin solution to the test tube labelled C.
4. The students then placed the 3 test tubes in water bath and left it for 5 minutes.
5. Following on they poured the contents of test tube C (rennin solution) into test tube A and start the stopwatch.
6. They examined the tubes, and then they tilted gently and did not shook it.
7. Furthermore, they recorded the time it takes for the clotting to occurred in both the test solutions (test A) and control (test B).
8. They repeated the above steps at temperatures of 0°C (use ice-cubes), 20°C (tap water), 60°C and 80°C.
9. Finally they repeated the entire experiment several times and noted the average results.

Risk Assessment:

The risk in this experiment involved is using Bunsen burner when preparing a water bath and this can cause burns. Also beware of broken glass (in case if a test tube is broken).

Safety procedures

The safety procedures involved in this experiment is when care was taken for water bath because it may be hot. Also care has to be taken for the Bunsen burner because it may cause burn to the skin and also were protective gloves from hazardous chemicals.

Variables

Independent: - Temperature

Dependent:- Is the rate of reaction(time taken for the milk to curdle).

Control Variable:-  Same amount of Rennin, same amount of milk, same concentration of Rennin, same type of milk and same amount of time the test tubes were left in water bath(5 minutes).

Results

Time taken for milk to curdle in the presence of Rennin  

Time taken for milk to curdle without the presence of Rennin

Discussion questions

1. The purpose is to compare the results. E.g. to see if the milk alone (in the absence of Rennin) could curdle.
2. Since the waste material was not harmful or dangerous, it was disposed through the sinkhole.
3. An example of destructive testing was the milk which has Rennin solution added to it. After the milk had curdled, it could not be used again. An example of non-destructive testing was the water bath, which could be reused; the temperature had to be changed.
4. Because it involves a number of tasks it is better so the results are more reliable and accurate. For example, while one person added Rennin solution someone else started the stopwatch.
5. The variable that were controlled were: amount of Rennin solution, amount of milk, concentration of Rennin, type of milk, amount of time test tube were left in the water bath prior to any mixing (5 minutes). These variables were controlled so they do not become a factor themselves. Only temperature was allowed to be a factor.
6. On source of error comes from the fact that the temperature of the water bath will fluctuate constantly. It needs to be checked and maintained regularly. Also, if care is not taken to observe the milk at regular intervals, one may not get the correct time at which it curdles.
7. The results were reliable because the experiment was repeated at the same temperature and the average was taken. Results were also compared with that of other group.
8. As temperature increases, so does the enzyme activity, up to a certain point. This is because as the temperature increases, the kinetic energy of the molecules also increases in the reaction, including the enzyme and this increase the speed of reaction decrease. However, after a certain maximum temperature, the enzyme’s structure becomes irreversibly changed. After this, the enzyme is said to be denatured and enzyme activity drops rapidly. This is because the changed shape of the enzyme does not allow it to become involved in further reactions. The maximum point before denaturation is called the optimum temperature. This is when enzyme activity is highest.  
9. The procedure used is a reliable way of investigating the effect of temperature on enzyme activity. However to get more reliable results, the experiment should be taken at shorter temperature intervals (e.g. 5-10°C)

Conclusion

Enzymes work best at optimum temperature. In the experiment, the optimum temperature was 40°C. This is because Rennin is produced by the walls of the stomach where the temperature is about 37°C. As temperature increase beyond the optimum, the enzyme activity decreases till it finally stops because enzyme is denatured. As temperature is decreased lower then the optimum, the rate of enzyme activity slows.

Bibliography