Paper 1 Flashcards
PRACTICAL
Enzymes
Cherrioal canotione are what mako you wark. And enzymes are what make them work.
Enzymes are Catalysts Produced by Living Things
wine things have tones of different chemical renotions going on inside them all the time.
Investigating Enzyme Activity
These renotions need to be safelully controlled - to get the fight amounts of substances in the ou
Will coon know how to investigate the effect of a variable on the rate of enzyme activity… I bet you’re thatled
you can raise the temperatire msued “og creature before its cells start getting damaged.
You Can Investigate How Temperature Affects Enzyme Activity
3) So living things produce
mat aer as
You Can Measure How Fast a Product Appears…
water bath at
constant temperature
measuring cylinder
amount of
per minute is
measured
biological catalysts.
A ontalyst is a substance which inoreases the speed of a reaction.
The enzyme catalase catalyses the breakdown
without being changed or used up in the reaction.
of hydrogen peroxide into water and oxygen.
delivery tube
useful chemical reactions in the body.
Enzymes reduce the need for high temperatures and we only have enzymes to speed up the
You can collect the oxygen and measure
how much is produced in a set time.
5) Enzymes are all proteins and all proteins are made up of chains of amino acids.
These reactions are called metabolic reactions.
3) Use a pipette to add a set amount of
These chains are folded into unique shapes
which enzymes need to do their jobs (see below).
hudrogen peroxide to a boiling tube.
Put the tube in a water bath at 10 °C.
Enzymes are Very Specific
4) Set up the rest of the apparatus as shown.
hydrogen peroxide solution
Add a source of catalase (e.g. 1 cm®
(eg potato)
of potato) to the hydrogen peroxide
2) A substrate is a molecule that is changed in a reaction.
1) Chemical reactions usually involve things either being split apart or joined together.
3) Every enzyme molecule has an active site — the part where a substrate joins on to the enzyme.
4) Enzymes are really picky — they usually only speed up one reaction. This is because
for an enzyme to work
a substrate has to be the correct shape to fit into the active site.
This is called the
‘lock and key’ model
because the substrate fits
into the enzyme just like
a key fits into a lock.
and quickly attach the bung.
Record how much oxygen is produced in the first minute. Repeat three times and calculate the mean.
Repeat at 20 °C
30 °C and 40 °C.
Control any variables (e.g. pH
the potato used
…Or How Fast a Substrate Disappears
The enzyme amylase catalyses the
active site
breakdown of starch to maltose.
solutions (at correct
temperature) mixed and
placed in water bath
2) It’s easy to deteot starch using iodine solution
— if starch is present
the iodine solution will
starch
and amylase
mocture sampled
every 10 seconds
dropping pipette
drop of
iodine solution
change from browny-orange to blue-black.
Temperature and pH Affect Enzyme Function
products
enzyme unchanged after reaction
3) Set up the apparatus as in the diagram.
spotung tile
Put a drop of iodine solution into each well
on the spotting tile. Every ten seconds
drop a sample of the mixture into a well using a
pipette. When the iodine solution remains browny-orange
(i.e. starch is no longer present) record the total time taken.
Repeat with the water bath at different temperatures to see how it affects the time taken
for the starch to be broken down. Remember to control all of the variables each time.
Rate of Reaction
1 This is the optimum temp.
where the enzyme is
Ja most active
1) Changing the temperature changes the rate of an enzyme-catalysed reaction.
Like with any reaction
a higher temperature increases the rate at first.
The enzymes and substrate have more energy
so they move about more
and are more likely to collide and form enzyme-substrate complexes.
But if it gets too hot
some of the bonds holding the enzyme together break.
This changes the shape of the enzyme’s active site
so the substrate won’t fit
any more.
The enzyme is said to be denatured.
You Can Also Investigate How pH Affects Enzyme Activity
All enzymes have an optimum temperature that they work best at.
1) You can adapt these experiments to investigate the effect of ph on enzyme activity.
4) The pH also affects enzymes. If it’s too high or too low
Follow the same method
but add a buffer solution with a different pH level to a series of
the pH interferes with the bonds holding the enzyme together.
Optimum - pwver
pH
different tubes containing the enzyme-substrate mixture.
This changes the shape of the active site and denatures the enzyme.
3) As before
control any variables
— use the water bath to keep the temperature of the reaction
5) All enzymes have an optimum pH that they work best at.
mixture the same for each pH
and make sure volumes and concentrations are kept the same.
It’s often neutral pH Z
but not always.
Paper 2
pH
If the lock and key mechanism fails - get in through a window…
Make sure you use the special terms like ‘active site and ‘denatured’ — the examiners will love it.
QI
Explan why cobytes nave an opamum pr. A hemperawne they wor best our. a mark
Section I - The Nature and Variety of Organisms
If only enzymes could speed up revision…
The key thing with experiments is to only change the thing you’re testing — and absolutely nothing else. Sorted
An experiment is carried out to investigate the effect of temperature on the breakdown of
hydrogen peroxide by the enzyme catalase.
Cubes of potato are used as a source of catalase.
Suggest two variables that would need to be controlled in this experiment. PH
he dig
1 volume
of.
(2 marks)
Section I - The Nature and Variety of Organism
