More on Enzymes

Question 1

Devise a method to investigate the effect of pH on amylase enzyme activity.

Answer 1

• Heat water to a constant 35°C
• Put two drops of iodine solution into each well of spotting tile as this will test for presence of starch - add 1 drop of pure starch to a well as a control
• Add 2cm³ of amylase enzyme solution to a test tube
• Place 2cm³ of starch solution into same tube
• Add 1cm³ of buffer solution with a pH of 5 to the tube
• Mix solution in test tube and place it into beaker of water
• Use pipette to remove few drops of solution every 20 seconds from test tube and put them into each well of spotting tile (except control)
• Repeat until iodine solution stops turning black (indicates no starch left)
• Record the time this takes
• Repeat with buffer solutions of different pH values to see how pH affects time taken for starch to be broken down

Question 2

(Exam-style question)

Answer 2

One from:

• All the starch has been converted into glucose
• All the starch has reacted with the amylase
• All the starch is digested

Question 3

(Exam-style question)

Answer 3

Any two from:

• pH of the solution
• Concentration of amylase
• Concentration of starch
• Amount of mixing
• Size of the tube used
• Time interval must be the same

Question 4

(Exam-style question)

Answer 4

One from:

• It is a control
• To check that starch doesn’t break down into glucose without amylase

Question 5

(Exam-style question)

Answer 5

• Mix starch solution with amylase
• Add buffers with different pH values to the solution
• The sample that produces glucose in the shortest time is closest to the optimum

Question 6

How can you calculate rate?

Answer 6

• Rate = change ÷ time
• Rate = amount of product formed ÷ time
• Rate = 1 ÷ time (for when you are not given how much something has changed during a reaction)
• Rate = 1000 ÷ time (for when you need larger results to plot on a graph)

Question 7

(Exam-style question)

Answer 7