8. Enzyme Controlled Reaction

Question 1

What RP is this ?

Answer 1

1

Question 2

Name 2 ways of measuring the rate of an enzyme controlled reaction ?

Answer 2

1. Measure how fast product is formed and use this to compare rate of reaction under different conditions
2. Measure how fast substate is broken down and use this to compare rate of reaction under different conditions

Question 3

What practical would you do if you are Measuring how fast product is formed and use this to compare rate of reaction under different conditions
?

Answer 3

Use Catalase which catalyses breakdown of hydrogen peroxide into water and oxygen.
It’s easy to measure volume of oxygen produce and to work out how fast it’s given off.
You’ll be working out rate of the reaction at different temps.
Oxygen displaced water from cylinder

Question 4

What do you need to do when measuring rate of a reaction ?

Answer 4

You need to find out how much the amount of reactant or product is changing over time

Question 5

What apparatus will be needed for investigation breakdown of hydrogen peroxide

Answer 5

Measuring cylinder 
Trough of water 
Boiling tube
Bung 
Delivery tube 

Hydrogen peroxide solution
Enzyme catalase

Question 6

How to carry out the experiment of breakdown of hydrogen peroxide

Answer 6

1. Set up boiling tubes with same volume/ conc of hydrogen peroxide (keep pH same add equal volume of buffer)
2. Set up rest of apparatus
3. Put each boiling tube in water bath at different temps (10,20,30..) along with another tube containing catalase. Wait 5 mins before moving on to next step so enzyme gets up to same temp .
4. Use pipette to add same volume/ conc of catalase to each boiling tube. Quickly attach bung / delivery tube.
5. Record how much o2 is produced in first minute of reaction - stopwatch
6. Repeat experiment at each temp 3 times and use result to find mean volume of oxygen produced.
7. Calculate mean rate of reaction at each temp by dividing volume of oxygen produced by time take.
   Units cm3 s-1

Question 7

Why Buffer solution added?

Answer 7

It resists changed in pH when small amounts of acid or alkali are added.

Question 8

What should also be carried out at each temp ?

Answer 8

Negative control reaction

Ie boiling tube containing hydrogen peroxide but NO CATALASE should be carried out at each temp

Question 9

What experiment would you do Measure how fast substate is broken down and use this to compare rate of reaction under different conditions ?

Answer 9

Using enzyme amylase to catalyse breakdown of starch into maltose.

Then using iodine potassium iodide solution to test for starch presence. To work out rate of reaction at different concentrations of enzyme.

Question 10

Apparatus you will need for investigation breakdown of starch

Answer 10

Stopwatch
Pipette
Spotting tile
Test tube

Starch solution
Amylase enzyme
Potassium iodide

Question 11

How to carry out experiment for investigating breakdown of starch.

Answer 11

1. drop of iodine potassium solution into each well on spotting tile. Labels wells
2. Mix together known conc/ volume of amylase and starch in test tube
3. Using pipette put a drop of mixture into one fo the Wells containing iodine solution at regular intervals ( every10secs)
4. Observing resulting colour. Iodine solution goes blue back when starch is present but remains normal browny orange colour when there’s no starch around.
5. See how fast amylase is working by recording how long it takes iodine solution to no longer turn blue back when starch/-amylase is added
6. Repeat experiment using different conc of amylase
7. Also sure you repeat experiment 3 times at each amylase conc and fine mean time taken

Question 12

What is key to these experiments ?

Answer 12

Only change one variable

Everything else should stay the same