MPI
This page available as pdf download

Amylase is an enzyme that catalyses the hydrolysis of starch. Iodine and starch react to produce a dark blue-black colour so iodine may be used as an indicator to show the rate at which starch is broken down. A light probe can be used to monitor the change in optical density. Used in this way the probe acts as a colorimeter.

1. Use the following steps to start the DataMate program on your TI-83 Plus Calculator:

   Press ,  (for TI-73, TI-82, and TI-83 Calculators: Press ) then press the calculator key for the number that precedes DATAMATE. Press . An introductory screen will appear, followed by the main screen.
    

2. Plug the Light Probe into channel CH 1 on LabPro or CBL2 interface
    
3. Arrange the light source so that it shines through the beaker and into the light probe. Use the black paper to shield the beaker from changes in ambient light level
    
4. Put 30 crn³ pH 7 buffer into the beaker. Add 20 cm³ starch solution and a few drops of iodine.

1. Start the DataMate program. Press to reset the program. DataMate will detect the auto-ID sensor, set the data collection parameters, and display the current sensor reading.
    
2. Press : SETUP and using the cursor buttons, or , select MODE press .
    
3. Select : TIME GRAPH and the screen TIME GRAPH SETTINGS will appear.
    
4. The default settings are 180 samples every 0.05s experiment will collect light readings for 9 seconds. To change this select : CHANGE TIME SETTINGS
    
5. Type in a time interval in seconds, press , then the number of samples press . The experimental length in seconds is then given this should be about 5 minutes (300s) for a trial run.
    
6. Press : OK then and again press : OK to return to the main screen.

1. Select : START to begin data collection, a double beep from the interface will confirm you are recording. You may stop data collection at any time by pressing the key
    
2. Wait about 10 seconds and add 5 cm³ amylase solution. A live graph will appear on the calculator screen.
    
3. After the data collection is complete the interface will beep again and an autoscaled graph of the data will appear.
   
   
4. A cursor will appear flashing on the y-axis. Use the or keys to examine the data points along the displayed curve of light vs. time. As you move the cursor right or left, the light (X) and temperature (Y) values of each data point are displayed below the graph. Move the cursor to the point when the amylase was added to the starch solution. Record that time. Move the cursor to find the highest light intensity and record that time. How long did it take for the amylase to digest the starch?
    
5. To return to the main screen press .

1. To save the data use the : TOOLS option, then : STORE LATEST RUN.
2. To see the stored data select : QUIT and press the key. Select : Edit your data should appear in L1 (time) and L2 (light intensity). You may now shut down the calculator and transfer the data to a computer for further processing in a program such as MS Excel using the TI Graph Link

• Which is the most appropriate recording method and why?
• What would happen if you repeated the experiment at a different temperature?
• At a different pH?
• With a different concentrations of starch?
• What if the amylase is boiled before use?
• What would you use as a control for these experiments?

• MPI Index
• Top of Page