pratical 3

• On a tile, label each well with the time (from 0 onwards) and add a drop of iodine solution to each well.
• Add 2 cm3​ ​of each buffer solution (ranging from pH 3.0 to 7.0) into each labelled test tube.
• Immerse the starch solution, amylase solution, and the test tubes of buffer solution in a water bath at 25​°C.
• Allow a few minutes for the temperature to equilibrate.
• Use a syringe to add 2 cm3​ ​of amylase into a test tube of buffer solution.
• Use a syringe to add 2 cm3​ ​of starch into the same test tube and start timing immediately.
• Use the glass rod to transfer a drop of the mixture to the well labelled ‘0’ on the tile.
• Repeat step 6 every minute, rinsing the glass rod in between every test, until the iodine solution remains brown and does not turn blue-black.
• Calculate the rate of enzyme reaction by using 1/ time taken for iodine solution to remain brown.
• Repeat steps 2-8 for buffer solutions with different pH values.
• Plot a graph of the rate of enzyme reaction against pH.