2. Organisation (Required practical 5 - investigating enzymatic reactions and the effect of pH)

Question 1

What is the practical?

Answer 1

How does changing the pH affect the time taken for amylase to break down all the starch

Question 2

What is the IV?

Answer 2

The pH

Question 3

What is the DV?

Answer 3

• The time taken for iodine to no longer change colour (surrogate)
• Or the time taken for amylase to break down all the starch

Question 4

What is raw data?

Answer 4

The measurements you directly get from the experiment

Question 5

What is the equation for rate?

Answer 5

Rate = 1000
—————-
time taken

Question 6

What is the CV?

Answer 6

• The volume of buffer
• The volume of iodine in each well of the spotting tile
• The volume and concentration of amylase and starch used

Question 7

What is the colour change of iodine in the presence of starch?

Answer 7

Browny-orange to a bluey-black

Question 8

What are the steps for the experiment? (8)

Answer 8

1. Get a spotting tile and add drops of iodine solution into each well
2. Next set up a bunsen burner, tripod, heat proof mat, gauze and beaker with warm water
3. Heat until 35 degrees celsius (try keep it constant throughout the experiment)
4. Get the boiling tubes and add 1cm^3 of amylase solution, buffer solution with a pH of 5, and 5cm^3 of starch solution
5. Leave to equilibrate in the beaker to the 35 degrees
6. Then mix contents together and start the stopwatch
7. Every 30 seconds add the solution from the boiling tube to the iodine in the spotting tile using a pipette
8. Repeat and use different pHs of buffer solution and investigate how that affects the rate of reaction

Question 9

How can the temperature of the warm water be kept constant throughout the experiment?

Answer 9

By using a thermometer and topping up the water when needed

Question 10

What does the buffer do?

Answer 10

It keeps the pH constant