-globular proteins. -biological catalysts. -have a specific tertiary structure. -they can be reused as they remain unchanged after a reaction. -they reduce the activation energy of a reaction.
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what is activation energy?
the amount of energy needed to get the reaction going.
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what happens?
bonds break so that there is energy to form new bonds so that the reaction can take place.
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larger activation energy =
slower rate because only a few substrate molecules have the energy to pass the barrier
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what is the active site?
where the reaction takes place
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what is it made up of?
a small number of AAs
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what is the substrate held in the active site by?
temporary bonds that form between the AAs of the active site and groups on the substrate molecule.
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what does the lock and key hypothesis suggest?
that the active site is complementary in shape to the substrate.
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what happens once the enzyme-substrate complex is formed?
intramolecular forces cause the bonds to break and form products.
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what does the induced fit hypothesis suggest?
that the active site is not initially complementary in shape to the substrate.
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how does it propose the enzyme-substrate complex is formed?
the substrate begins to bind to the enzyme and induces the active site to change shape to fit that of the substrate
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what is the optimum temperature for mammalian enzymes?
40c
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what happens when temperature increases?
the molecules have a higher kinetic energy and so enzymes collide with their substrate more often.
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what about at temperatures below 0?
enzymes work at a very slow rate due to the slow diffusion of enzyme and substrate molecules through the ice lattice.
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what happens when the temperature goes above the optimum?
enzyme denatures
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why are enzymes relatively resistant to high temperatures?
they have a high proportion of cysteine which makes disulphide bridges, making them stronger and more resistant.
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what is the optimum pH for most enzymes?
pH7-8
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what do changes in pH do?
disrupt the arrangement of hydrogen bonds
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what does this cause?
the specific 3D shape of the active site to denature so that the substrate can no longer bind
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what happens as the substrate conc increases?
the rate increases because there are more substrate molecules to bind with
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what happens at higher concs?
the rate is constant because the enzymes are saturated with substrate so there are few free enzymes
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what is the maximum RoR at eh infinite substrate conc called?
V max
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what do inhibitors do?
reduce the rate of enzyme-catalysed reactions
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how do competitive inhibitors do this?
they are a similar shape to the substrate and so fit into the active site meaning that the substrate cannot
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what happens if the substrate conc is high enough?
the effect of the competitive inhibitor is removed and V max will be reached
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what do non-competitive inhibitors do?
bind to the allosteric site which changes the whole shape of the enzyme so that the substrate can no longer bind
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is it reversible?
no
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give 3 examples of non-competitive inhibitors.
-cyanide. -heavy metal ions. -some insecticides.
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what do non-competitive inhibitors show?
that the lock and key hypothesis is incorrect
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Other cards in this set
Card 2
Front
what is activation energy?
Back
the amount of energy needed to get the reaction going.
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