To investigate the effect of pH on the activity of the enzyme Trypsin

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To investigate the effect of pH on the activity of the enzyme Trypsin

Aim

To investigate the effect of pH on the activity of the enzyme Trypsin using a range of buffer solutions and exposed photographic negative.

Hypothesis

Trypsin will have an optimum pH (the rate of reaction will be highest at that pH) and the rate of reaction will decrease below and above the optimum pH.

Apparatus

3% trypsin solution

Buffer solutions at pHs 3,5,7,9 and 10

5 pieces of exposed photographic negative (1.5cm2)

5 pieces of wire (about 15cm long)

5 test tubes

2 10cm3 graduated pipettes

2 Pipette fillers

thermostatically controlled water bath

thermometer

stop clock

Method

The 5 pieces of exposed photographic negative were put onto the ends of the 5 pieces of wire.

5cm3 of trypsin solution was put in to a test tube. 2cm3 of buffer solution at pH 7 was added to the test tube. The test tube was put into the water bath (set at 25?C) and it was preincubated for 5 minutes so that the contents of the test tube would reach the temperature of the water in the water bath. The temperature of the water in the water bath was taken using a thermometer. It was 26?C.
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A water bath was used so that the temperature would be the same for all the pHs because the temperature of the laboratory varies.

Then 1 piece of negative, on the end of a piece of wire, was dangled into the test tube.

The time taken for the negative to become clear was measured using a stop clock. The photographic negative is coated with a layer of gelatine containing crystals of a silver salt. The trypsin hydrolyses the gelatine (protein), to polypeptides and amino acids, and you can see when this has happened because the silver ...

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