Lesson 1: RP Amylase pH's

Question 1

What happens to enzyme activity as you increase pH?

( Away from optimum temp)

Answer 1

• Lowers enzyme activity

Question 2

What happens to enzyme activity when you increase pH?

(away from optimum pH)

Answer 2

• Enzyme activivity decreases

Question 3

What is the independent variable in this experiment?

Answer 3

pH of buffer solutions

Question 4

What is the dependent variable in this experiment?

Answer 4

• Enzyme activity

Question 5

What is the control variable in this experiement?

Answer 5

• Temperature
• Type of enzyme used

Question 6

What are the 7 main steps to this practical?

Answer 6

1.) Add 1 drop of iodine to each depression of spotting tile.
2.) Place 2cm³ of amylase, starch and pH5 buffer in 3 different testubes
4. ) place in electric heater at 35 degrees for 10 mins .
5. ) Use thermometer (in each test-tube to check that each solution has reached the same temperature.)
5.) Add all testubes together and put drop of solution in spotting tile. This is sample for 0 secs.
6.) Put it back in heater and start stopwatch
5.) Use pipette to transfer solution to an iodine well every 30 secs.
7.) Record time iodine doesn’t change colour
8.) Repeat steps 1-6 for different pH’s

Question 7

Give 2 issues with this practical.

Answer 7

• Colour change isn’t clear
• Only testing sample every 30 secs

Question 8

What is the issue with only testing your sample every 30 secs?

How can it be solved?

Answer 8

• Only get approximate time at which reaction is complete.

Take sample every 10 secs .

Question 9

What are buffer solutions?

Answer 9

• Solutions with different PHs.

Question 10

How can we solve the problem that the colour change isn’t always clear?

Answer 10

• Get several people to look at it.

Question 11

Why do we keep testube in electric heater when taking samples?

Answer 11

• To keep temp constant.

Question 12

Q.)

How can you find a more exact optimal pH?

Answer 12

• Use smaller intervals.

Question 13

When I want to see THE OPTIMAL TEMPERATURE for enzyme action why do I use 30 sec intervals?

Answer 13

• To see how long it takes for there to be nothing but fatty acids using universal indicator.

Question 14

Q.)

Amylase catalyses the breakdown of starch into maltose. 15 grams of starch were added to a solution containing amylase. It took 2 hours for all the starch to be broken down. Calculate the rate of reaction.

Answer 14

Rate = Change ÷ Time

(In this case, Rate = Amount of substrate used ÷ Time)

Rate = 7.5 g / hr or 7.5 g hr⁻¹

Question 15

Q.)

At pH 6 the time taken for amylase to break down all of the starch was 50 seconds. Calculate the rate of reaction at pH 6.

Answer 15

• Rate = 1000/ time
• 1000/50 = 20s⁻¹

s⁻¹ means per unit time

Question 16

What does rate mean?

What is unit for rate?

Answer 16

Per unit time

cm/s (per ) s⁻¹ (unit of time)

Question 17

Q.)

(f) There are different ways to investigate the breakdown of starch by amylase.

One other method is to measure the concentration of starch present in the solution every 30 seconds.

Why is this a better method ?

normal way of doing practical

Answer 17

• It is more accurate
• As it is a quantitative value.