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