* Repeat steps 4 & 5 (for the amylase & starch solution mixture) every 30 seconds until a blue/black colour no longer develops.
* When there is no further change in the colour of the iodine, take the starch-amylase test tube, add Benedict's reagent, and place in the water bath for 1 minute.
but i have decided not do do a pilot experiment.
To ensure that the test is fair I will only vary two factors (at different stages of the experiment not simultaneously). All the quantities will have to be carefully measured since small variations in the amount of enzyme used can make significant variations in the results. In the section where temperature is investigated, 2cm3 of water is added. This is because the starch solution is neutral and in the previous investigation (for pH) 2cm3 of the appropriate buffer was added. If the 2cm3 of water was not added then it would not be a fair test since the volumes used in each part of the investigation would be different. If they were different then this would affect the results since the solution would be of different concentrations and therefore one would react faster than the other would.
Apparatus
I have chosen to use a measuring cylinder to measure the volumes of substances used since it is more accurate than a pipette. I will use an electronic water bath for maintaining the mixture at a temperature above room temperature since the temperature is more accurate than a water bath above a Bunsen burner. I will have to use ice from the freezer to reduce the temperature of the mixture to 10 C and the different temperature. A 100⋄C thermometer will provide temperature results of a sufficient accuracy (to 1OC). The pH buffer range will be pre-prepared therefore I do not have to concern myself with measuring and maintaining pH levels.
* Variables
I have chosen to repeat the experiment 3 times because it therefore allows me to calculate an average time. This will ensure that there are no abnormal results and it will increase accuracy. I have decided to start the temperature at 10OC and increase by 5OC each time since it will allow me to see the increase and decrease of the enzyme activity. It should also be accurate enough for me to predict an optimum operating temperature to an accuracy of 5OC. I have no control over which pH buffers I will use since the school prior to the experiment will provide them.
* Enzymes
Substances called catalysts speed up many chemical reactions. Catalysts called enzymes control the metabolic reactions in the body. Amylase is an enzyme; it is present in the digestive systems of many animals. Amylase speeds up the breakdown of long chain starch molecules in smaller chains of maltose. Enzyme molecules have a very precise three-dimensional shape. This includes a 'dent', which is called the active site. It is exactly the right size and shape for enzyme's substrate to fit into (in the case of amylase this is starch). When a substrate molecule slots into the active site, the enzyme 'tweaks' the substrate molecule, pulling it out of shape and making it split into product molecules. High temperatures make enzymes inactive: this is because they are proteins, which are damaged by temperatures above about 40OC. Most enzymes work best at a pH of about 7. This is also because they are proteins, which are damaged by very acidic or very alkaline conditions. Due to the enzyme's unique active site it can only convert one kind of substrate molecule into one kind of product.
First of all the average time taken for the starch to be digested in each condition was calculated. got these averages off the internet and have incorporated these and i will draw a graph to help me.
Temperature(C) 10 21 32 40 50 55 60 67 80&90
Average Time (min) 9.8 6.7 5.3 5.5 3.5 3.0 3.5 4.5 10 +
pH 8 7 6 5 3 2
Average Time (min) 9.5 6.7 4.5 2.8 4.7 9.2
research
i have used the internet and books such as the history of enzymes.
diagram
results this is the first second and third attempt now to be put in a graph like the one shown below but i will also show the average all shown in seconds.
30c 50,60,50
40c 30,41,47
50c 140,130,140
10c 160,170,160
analysis and conclusion
i have found out that the best temperature is in between 30 and 40 degrees Celsius but if i had more time i would repeat and a more accurate time scale and i would also repeat it more.
my graph shows the rate of reaction against the temperature as you can see the more you increase the
temperature the quicker the reaction goes until it reaches a maximum
speed and then it begins to decrease i believe that the maximum temperature is in between 30 and 40 degrees.
my prediction was correct because as the temperature increases the rate of reaction is quicker until a maximum and then it falls quickly.
they agree with the background research i have done from a book called the fullick book and the book i had of the history of enzymes with help from some friends but altered into my own words and have recorded this above.
evaluation
the procedure went well as thought the things i would change would be the accuracy of the temperature in this it's showing that the range is in between 30 and 40 for human amylase the rate must be close to 37 degree which is ideal for the temperature for the reaction also if measurements every 5 seconds and a tolerance chart for when it is complete gone also check my conclusion for the total and what the main evaluation i repeated my experiment incase of rogue values but as i have repeated the total to get a wide variety of results
