Effect of PH on enzyme-catalyzed reactions
Through the second experiment-effects of pH on enzyme-catalyzed reactions, we get PH and absorbance of whole 5 sample with the use and compare of blank sample. No.1 sample with PH 3 and the absorbance is 1.76. No.2 sample with PH 5 and the absorbance is 1.08. No.3 sample with PH 7 and the absorbance is 2.98. No.4 sample with PH 9 and the absorbance is 0.51. No.5 sample with PH 11 and the absorbance is 0.98.
Table: Effect of PH on extent of browning
| Sample | PH | Absorbance |
| Blank | * | 0 |
| 1 | 3 | 1.76 |
| 2 | 5 | 1.08 |
| 3 | 7 | 2.98 |
| 4 | 9 | 0.51 |
| 5 | 11 | 0.98 |
Graph: Effect of PH on the browning rate
· Discussion and Conclusion
To draw the results of temperature experiment, the curve is like a “mountain”, it goes up from 0°C and reaches the peak at 40°C and down to bottom at 60°C. As we can see, the best temperature for the rate of reaction is 40°C with 3.86 absorbance. In contrast, the lowest rate of reaction is 1.51 absorbance at 60°C. Obviously, our hypothesis was accepted because the rate of an enzyme catalyzed reactions is greatest at temperature that are 40°C. For a reaction to occur, the two reactant molecules must “bump into” each other; however, in this experiment, when the temperature at 0°C, the cold condition slow down the speed of molecules and enzymes, so that it directly decreases encounters between substrate and enzymes. Therefore, 2.34 absorbance at 0°C is not high like high temperature, and enzyme that under cold condition won’t highly efficiency like enzymes under higher temperature. Moreover, high temperature does not necessarily increase the efficiency of the enzyme. Just like enzymes at 1.51 absorbance at 60°C, it not efficiency like enzymes at 3.86 absorbance at 40°C.Why? Because enzymes are efficient in a narrow rang of temperature. It true that higher temperature makes enzymes fast and efficient, but once the temperature higher than a certain temperature, the enzymes become denatured. It means enzyme lose its shape and even not reactive like enzymes under low temperature condition.
Moreover, the PH experiment pattern just like the letter “W” in graph, it reaches the peak at PH 7. As we can see, the greatest rate of reaction at PH 7 which is 2.98 absorbance. The lowest rate of reaction is 0.51at PH 9. Our hypothesis was accepted because the rate of an enzyme catalyzed reactions is greatest at Ph values that are PH 7. To explain the change of the absorbance at low and high PH values, the best environment for enzymes’ reaction is neutral condition, since acid and basic environment will make enzymes become denatured. It means enzymes will lose their original shape when they are under acid and basic condition. As a result, 1.76-1.08 absorbance under acid condition and 0.51-0.98 absorbance under basic condition are not high as 2.98 absorbance under neutral condition which is PH 7. Moreover, some people know that the greatest rate of reaction for few types of enzymes are not PH 7(neutral condition), and their optimal PH is even around PH 2 which is true. Actually, in human body, typical enzymes are still highly efficient at PH 7 environment. However, some parts of human body may have a acid environment, like stomach; thus, enzymes that optimal PH is 2 would be found in acid environment like stomach.
Fortunately, earth is our home, and earth make us have nice environment to live. Some people may not live in optimal temperature rang; thus, once their enzymes not work in optimal range for a long time, they will start ill. Different like human being, there are few kinds of animals that live in extreme weather are able to properly adjust their enzymes’ efficiency, like penguin, white bear, deep-sea fish and dolphin. Actually, study what factors affect the enzyme is only a small step for natural science, there are lots of things that unknown wait for human to explore and study.
0°C Room temp 30°C 40°C 60°C 2.34 3.23 3.48 3.86 1.51
Temperature of water bath (°C)
Absorbance
Absorbance
3 5 7 9 11 1.76 1.08 2.98 0.51 0.98
PH
Absorbance