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1.10 Core Practical - Effect of pH on Enzyme Activity - Coggle Diagram
1.10 Core Practical - Effect of pH on Enzyme Activity
Intro
We can use iodine (dark orange colour) to check for the presence of starch in the solution at any time
When starch is present, the iodine solution will turn to a blue-black colour
The enzyme being used is called amylase - which breaks down carbohydrates such as starch into simple sugars such as maltose
Amylase has an optimal pH, and we can use this experiment to estimate what it might be
In this practical, we are looking at how pH affects the rate of activity of a particular enzyme
Equipment
1% starch solution
Iodine solution
1% amylase solution
Labelled buffer solutions of different pH
Method
Label a test tube with the pH to be tested. Place it in a water beaker with 50ml cold water and place this above a Bunsen Burner for 3 minutes
Place 2cm^3 of amylase solution, 2cm^3 of starch solution and 1cm^3 of the buffer pH solution in a test tube and start a stopwatch
Place single drops of iodine solution on each well of a tray
Repeat Step 4 after another 10 seconds. Continue repeating until the solution remains orange, and record the time taken
After 10 seconds, use a pipette to place a drop the solution into one of the wells containing iodine solution. The mixture should turn blue-black to indicate that starch is still present and has not yet been broken down.
Repeat Steps 1-5 with a buffer solution of different pH
Record your results on a graph of pH (on the x-axis) and time taken to complete reaction (on the y-axis)
What results do we expect to see?
The optimal pH of amylase will be at whichever pH the reaction completes in the shortest time
This should be somewhere around pH 7.0
Why do we use a Bunsen Burner and water beaker?
We use this equipment to keep the solution at a relatively constant temperature throughout the reaction (temperature is a control variable in this experiment)