Picture Source: http://www.abbysenior.com/biology/enzymes.htm
There are three different types of enzymes that we can name, they are:
- Amylase – This is commonly found in saliva and is used to break down long chains of carbohydrates such as starch into Maltose and Dextrin
- Lipase – This is commonly found in the stomach and is used to break down fats.
- Protease – This is also found in the stomach and is used to break down Proteins. The experiment being used in this experiment, Pepsin, is a protease and breaks down proteins into peptides.
Source: http://www.wikipedia.com
Method:
Start by checking the room temperature, and if it is below the first temperature you have set for the test then heat up a water bath with a Bunsen burner until it is at the correct temperature, this will ensure for a fair test. Once the water is at the set temperature, in this experiments case it is 24°C, take the Bunsen burner away from the water bath and put a test tube into the water bath. Then into the test tube put 3 cm³ of Pepsin, and then put the same amount of substrate into the test tube and start the timer. Putting the same amount of enzyme and substrate in every time and ensuring that the timer is started as the substrate is entered will ensure a fair test. Then time how long it takes for the solution to reach the set clearness using the Clearness chart. In this case it is 3. Make sure that you check the clearness of the solution every 10 seconds ensuring a fair test. Once the solution has reached the set clearness, record the time it has taken to reach the clearness and repeat the experiment but at a higher temperature, making sure that the water is at the exact set temperature and the same amount of enzyme and substrate is added each time to ensure a fair test. The experiment will be repeated 3 times to make the results more certain and there will be results taken at 7 different temperatures taken at 10 second intervals from 24°C to 84°C.
Results:
The temperature in this set of results is the temperature outside the test tube, in the water bath.
The temperature in this set of results is the temperature inside the test tube.
Conclusion:
The results show that as the temperature increases, the enzyme starts to work faster, but, the rate at which the enzyme speeds up, gets lower. For example, looking at the first graph, at the start of the first run, the enzyme goes from taking 88 seconds to break down the substrate enough, to taking 62 seconds. Then looking at the last two results from the first run it goes from taking 15 seconds at 74°C to taking 13 seconds at 84°C. This is shows that the enzyme is starting to denature. Although enzymes usually start to denature around 60°C, it would have taken a few seconds for the inside of the test tube to get to the same temperature as the temperature in the water bath. What is shown in the graphs is what was predicted, as the temperature increases the rate that the enzyme works will increase, until a certain point where the enzyme will denature.
Analysis:
The results that are shown above are reliable; although another run could have been taken in the second set of results to make them more accurate and more reliable, they both effectively show the same thing, that as the temperature increases the rate at which the enzyme works increases, until a certain point where it will start to denature, around 54°C in the case of the first set of runs, whereas in the second set of runs it is harder to tell. Denaturing occurs when the enzyme starts to breakdown; its shape changes as the protein strings that it is made of start to break apart. If the enzyme starts to change shape, it means that the substrate the enzyme is breaking down will no longer be able to fit into the active site on the enzyme. This causes the rate at which the enzymes break down to slow down, as there are less successful collisions occurring. Although the heat has increased and the substrate and enzymes are moving faster, the enzymes cannot work if the substrate doesn’t fit into the activation site. So the activation energy might be reached, and there might be a higher chance of a collision, but without the substrate fitting onto the activation site the rate at which the enzymes work will slowly decline until all have denatured.
Evaluation:
The results show what was expected, even though there were mistakes made in the second set of results. The first set of results went well, but to make the results more accurate, I could have used a water bath where the temperature is kept constant and accurate, instead of using a beaker filled with water and a Bunsen burner; which made it harder to keep the temperature constant and accurate. The second set of results didn’t go as well because it was difficult the keep the temperature inside the test tube at the set temperature after putting in the enzyme and substrate. One way that this could have been improved would be by putting only the enzyme in the test tube while it was being heated and then adding the substrate. Both set of results show that as the temperature goes up the speed at which the enzyme works also goes up, until a point where it will start to denature. Instead of just measuring the temperature, the pH of the liquid could have also been measured, as the pH is another factor in the denaturing of enzymes. If the pH is too high, the enzyme will start to denature the same as with temperature; and if the pH is too low the enzyme will not work as fast, the same as with temperature. One way that the pH could have been kept constant, if it was measured, is to use universal indicator paper to measure the pH every time there was a temperature result taken. If the pH became too acidic, a small amount of alkali could be added to it to return it to normal; and if the pH became too alkali, a small amount of acid could be added to return it to normal. The optimal pH for the enzyme in this case is pH 2, which means that the solution would have to be kept quite acidic at all times.
