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16 Cards in this Set
- Front
- Back
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What do enzyme-catalysed reactions in vitro usually need extremes of?
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Temperature
Pressure pH Concentration |
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Do enzymes affect the free energy of a reaction?
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No, they enable the reaction to overcome a kinetic barrier
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Describe 3 ways in which enzymes promote a reaction to occur
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Orientation - may hold two substrates together in the appropriate position for the reaction
Reactive group - enzyme binds with substrate transiently during reaction Proton donors - some enzymes act as proton donors |
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Describe 2 ways in which enzymes are specific
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Structure of substrates
Types of reaction they catalyse |
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Name 5 different factors that may change the rate of an enzyme-catalysed reaction
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Temperature
pH Concentration of substrate Concentration of enzyme Time course of reaction (conc. of product) |
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How does temperature affect the rate of reaction?
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Approx. x2 per 10 degree rise
until denaturing at too high temperatures |
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How does pH affect an enzyme-controlled reaction?
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Acts by protonating or deprotonating an ionisable group on the enzyme or the substrate
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What is Vmax?
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The enzyme's maximum rate
(enzyme becomes saturated with substrate) |
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What is Km?
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The Michaelis constant - the concentration at which the rate of the enzyme reaction is half Vmax
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What are the units of Km?
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Substrate concentration units
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Why is it difficult to estimate Vmax and thus Km?
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Vmax never reached
Hard to align a curve to a scatter of points Some enzymes inhibited by high [S], so readings at high [S] unreliable |
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What does this curve represent?
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Rate/[E]
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What does this curve represent?
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Rate/[S]
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What does this curve represent?
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Rate/pH
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What does this curve represent?
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Rate/temperature
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What does this curve represent?
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Rate/time course of reaction ([P])
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