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effect of ph on enzyme
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| Words: 346 | Submitted: 01-Apr-2011
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Descriptionbuffer solutions to provide range of Ph
Experiment 3. The effect of pH on the action of amylase on starch
(a) Draw up the table given below, in your notebook.
(b) Label five test-tubes 1-5.
(c) Using a syringe or graduated pipette, place 5 cm3 1% starch solution in each tube.
(d) Add acid or alkali to each tube as indicated in the table below, rinsing the syringe or graduated pipette when changing from sodium carbonate to acetic acid.
(e) Place several rows of drops of dilute iodine solution on a spotting tile. Half fill a beaker with water for rinsing the dropping pipette later during the experiment.
(f) Note the time and, using a syringe or graduated pipette, add I cm3 amylase solution to each tube. Shake the tubes to mix the contents. (See Figure on p.2)
(g) Using a clean dropping pipette, remove a sample from each tube in turn and let one
drop fall on to one of the iodine drops. Rinse the pipette.
(h) Continue sampling at intervals, taking samples most frequently from the tubes which
are beginning to give a purple or reddish colour with the iodine. When a sample fails
to give a blue or purple colour with iodine, note the time and stop taking samples from
(i) If after fifteen minutes some samples are still giving a blue colour with iodine, there is
little point in continuing to test the mixture in these tubes.
(j) Rinse the dropping pipette and use it to remove a sample from tube I. Touch the tip
of the pipette on to a piece of pH test paper so that a small quantity of liquid runs on
to it. Compare the colour produced on the paper with the standard chart supplied.
Repeat this for each tube, rinsing the pipette between samples.
(k) With a fresh piece of pH paper, test the pH of your mouth.
(l) Complete the table of results.
Starch solution and amylase plus:
Time for blue colour to cease appearing
1 cm3 sodium carbonate solution
0.5 cm3 sodium carbonate solution
2 cm3 ethanoic (acetic) acid
4 cm3 ethanoic (acetic) acid
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