ICT IN BIOLOGY
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Hydrogen peroxide (H₂0₂) is a toxic substance produced by the metabolism of cells. To stop this substance building up they break it down into water and oxygen. This reaction is catalysed by a group of enzymes called peroxidases. The reaction is exothermic, it releases heat energy.

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 Temperature Probe into channel CH 1 on the CBL2 interface.
    
3.  Press .
    
4. Check that you are getting a reading at about room temperature. If you get –999.9°C you know something is wrong! You will need to specify the probe. Press to reset the program, then reboot DataMate.
    

   WARNING

   Hydrogen peroxide is corrosive, avoid contact with the skin and the eyes and wear safety glasses. Wash off any spills with plenty of water.

    

5. Measure 10cm³ H₂O₂ into a large test tube. Slide the temperature probe into to the H₂O₂ and let it come to the temperature of the liquid (let the probe equilibrate). What would happen if you did not do this? How do you know if the probe has equilibrated? How long did this take?

1. Start the DataMate program. DataMate should 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 (be patient it’s a bit sluggish!)
   select MODE press .
3. Select : TIME GRAPH and the screen TIME GRAPH SETTINGS will appear.
4. The default settings are 180 samples every 1s experiment will collect temperature readings for 3 minutes. 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. A live graph will appear on the calculator screen. Wait about 15 seconds and add 2cm³ yeast suspension and stir it in.
    
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 cursor
   keys or to examine the data points along the displayed curve of temperature vs. time. As you move the cursor right or left, the time (X) and temperature (Y) values of each data point are displayed below the graph. Move the cursor to the point when the yeast was added to the hydrogen peroxide. Record that time. Move the cursor to find the highest temperature and record that time. How long did it take for the yeast to raise the temperature of the test tube to this point?
    
5. To return to the main screen press .
    
6. Wash the temperature probe and wipe it dry.

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 (temperature). You may now shut down the calculator and transfer the data to a computer for further processing in a program such as MS Excel or Star Calc using the TI Graph Link. Alternatively you may store and archive your data under another name for later analysis.

• Write out a balanced equation for this reaction. Note: catalysts such as enzymes are not consumed by the reactions they influence, they simply make them easier to react.
• How could you confirm that the enzyme has not been used up by the reaction?
• Which is the most appropriate recording method and why?
• What would you use as a control for these experiments?
• From the graph it should be possible to calculate the approximate rate of reaction in as rise in temperature per unit time or °C min^-1
• Repeated the experiment with different concentrations of hydrogen peroxide? (Store and archive your data first)
• What sources of error are there in this experiment (list at least three)?
• What would you do to improve the reliability and accuracy of this investigation?