Required Praxtical: Effect of PH on amylase

Aim of the practical

To investigate the effect of pH on the rate of enzyme activity using amylase

Independent variable

pH (changed using buffer solutions)

Dependant variable

Time taken for starch to be broken down (or rate of enzyme activity)

Control variables

Temperature

Volume of amylase

Volume of starch

Concentration of amylase

Concentration of starch

Step 1

Place drops of iodine solution into the wells of a spotting tile

Step 2

Add amylase, starch and a buffer solution to a test tube

Step 3

Place the test tube in a water bath at 37C

Step 4

Start the stopwatch and mix the solution

Step 5

Every 30 seconds, place a drop of the mixture onto the iodine

Step 6

Record the time when the iodine stays brown (no blue-black colour)

Likely results

Rate of reaction increases as pH approaches the optimum pH (about 7)

Rate decreases either side of the optimum

At extreme pH values the enzyme denatures and stops working

Graph axis

X axis=pH

Y axis=Rate of Enzyme activity

Shape=curve with a peak at the optimum pH

Common mistakes

Judging colour change by eye as it is subjective

Temperature not kept constant

Inconsistent timing

Improvements

Use a colorimeter instead of judging by eye

Use a water bath to control temp

Repeat results and calculate mean

Use automated timing or consistent intervals