Effects of pH on enzyme-catalyzed reactions
Materials
1. 6 test tubes with a test tube rack
2. a wax pencil
3. a pipette
4. spec 20
5. potato extract
6. water
7. catechol
8. distilled water
9. 5 different buffer solutions (PH 3, PH 5, PH 7, PH 9, PH 11).
Method
1. We use a wax pencil to mark the tubes with numbers 1 through 5 and “X” and leave the last tube as “blank”.
2. We measure 1 ml potato extract and 4 ml buffer for pH 3 into No.1 tube. Measure 1 ml potato extract and 4 ml buffer for pH 5 into No.2 tube. Measure 1 ml potato extract and 4 ml buffer for pH 7 into No.3 tube. Measure 1 ml potato extract and 4 ml buffer for pH 9 into No.4 tube. Measure 1 ml potato extract and 4 ml buffer for pH 11 into No.5 tube. Measure 1 ml potato extract and 4 ml buffer for pH 7, plus 2 ml distilled water into “Blank” tube.
3. Cover each tube with parafilm and invert to mix. Stand all 6 tubes in the test tube rack.
4. Add 2 ml of catechol to the 5 sample tubes, put the parafilm back on, and again invert the tube to mix the contents.
5. Use our “blank” to calibrate the Spec 20.
6. Allow the browning reaction to proceed for exactly 5 minutes. Then insert the sample tubes, one at a time in numerical order, into the Spec 20 and record the absorbances. Note any color changes in the test tubes.