4. Enzyme Kinetics Flashcards
how do enzymes affect equilibrium?
they dont!! just speeds up the reaction
what does a reaction coordinate diagram show?
shows the reaction progress
what is the transition state?
barrier of energy that must be overcome to react product
what would happen if there was no transition state?
substrate wouldn’t be stable
how do enzymes affect transition state?
enzymes allow for a new transition state by lowering the energy barrier
they do this setting up an optimal substate position, weakening the bonds with environment, etc to allow smooth transition from substrate to product
what does the speed of enzymatic reaction rely on?
rate of reaction, determined by transition state
what does equilibrium depend on?
equilibrium depends on the energy difference between the substrate and product –> not affected by enzyme
describe what happens at transition state and how
substrate undergoes structural changes –> bonds breaking and making, unstable intermediate
what is activation energy? how do enzymes affect it?
energy required to induce the structural change of the substrate at the transition state
enzymes reduce it –> faster reaction
is there a specific direction a molecule is more likely to go thru?
no direction –> equally likely a molecule decays in either direction, i.e. substrate or product
what is the active site?
specialized pocket where reaction occurs
what is the environment of the active site? why?
hydrophobic to isolate itself from water
how does the active site work?
allows reactants to be properly positioned to easily attain their transition state by weakening bonds
(may participate in reaction)
does the active site have stronger interaction with transition state, substrate, or product?
transition state
what would be the result if an enzyme’s active site was complementary to the substrate?
substrate is too stabilized –> cannot reach transition state and enzyme acts as competitive inhibitor of the transition state –> no drive to catalyze anything
what would be the result if an enzyme’s active site was complementary to the transition state?
substrate can fit into enzyme but not perfectly –> can reach transition state naturally but FASTER!
What is the induced fit model of binding?
active site approximates the substrate, then properly binds once substrate is there
what is the selected fit model of binding?
active site changes conformation constantly and ligand stabilizes 1 conformation
describe the equilibrium of enzyme activity
E+S <–binding–> ES <–catalysis–> EP <–release–> E+P
each step is in equilibrium and has diff transition state
what do serine proteases do?
cleave peptide bonds
describe the 3 components of the serine protease active site
- Ser –> OH group acts as nucleophile that attacks peptide bond of substrate
- His –> accepts H from Ser OH to make nucleophile
- Asp –> H bonds with His, making N more electronegative
describe the alkaline phosphatase experiment
to see how fast substrates are consumed by phosphatase
if phosphatase consumes NPP (colourless), will produce NP (yellow) and can measure amount of yellow
