Enzyme Mechanisms Flashcards
what do catalysts not affect
free energy change of a reaction
catalysts ______ alter the equilibrium concentratiosn of products and reactants
do not
enzymes typically accelerate reactions by factors
greater than 10^6
reasons why enzymes are amazing protein catalysts
- enzymes have amazing catalytic power
- enzymes have exquisite specificity
- enzymes operate under mild biological conditions
cofactor
any non-amino acid chemical component of an enzyme
coenzyme
a complex organic or metalloorganic molecule that binds non covalently
prosthetic group
tightly bound or covalently attached cofactor (like the heme in hemoglobin)
polypeptide component
apoenzyme
polypeptide component with cofactor attached
holoenzyme
do cofactors change by the reaction?
no, if they did change they would be substrates
what do enzymes do for ts and free energy
reduce free energy needed to achieve transition state
at the end of the reaction, what is the free energy state of catalyzed and uncatalyzed
da same
enzymes accelerate
both the forward and reverse reactions
what is reaction rate proportional to
concentration of x double dagger
what is x double dagger
conformation of substrate that must be achieved in order for chemistry to work
catalysts do what to the Ea of rxns which increases what
catalysts lower the activation energy of reactions which increases concentration of x double dagger
reaction energy reduction can be
60 - 100 kj/mol
_____ - fold shift in equilibrium for each ______ kj/mol free energy change
10 fold, 6
E+S transient blip why
increase in delta g becayse enzyme bingind to substrate decreases entropy
ES transient blip why
decrease in delta g because enthalpy decreases
EP transient blip why
increase in delta g because breaking bonds increases free energy bc enthalpy increases bc h bonds satisfied with water instead of protein itself
electrostatic catalysis
preferential binding to the transition state through complementary noncovalent interactions
which component does electrostatic catalysis stabilize
stabilize enthalpic component
entropy reduction
binding of substrates in a way that optimizes their proxumuty, orientation, and conformation for reaction
what component foes entropy reduction stabilize
entropic
induced fit
change in conformaiton of the active site opon substrate binding renders the enzyme catalytically active (gives substrate specificity)
transition state stabilization catlytic strategies
- electrostatic catalysis
- entropy reduction
- induced fit
metal ion catalysis
yse of metal ion cofactors, often to promote the formation of OH-
covalent catalysis
alter reaction pathweay to include intermediates with covalent bonds not in reactants or products
general acid-base catalysis (GABC)
use of functional groups that alternately act as acuds and bases, often for reactions incoloving H+ transfer
which major catalystic strategies are new intermediates in reaction pathway
metal ion catalysis
covalent catalysis
general acid-base catalysis
which major catalytic strategy is very common
general acid-base catalysis
why does enzymes enforcing proper positioning lower activation energy
less entropy reduction required to reach x double dagger
what is the cost for bringing two molecules into proximity to form one molecule
entropy
how does enzyme binding pay for the ____ cost?
entropy cost, using multiple noncovalent interactions between the enzyme and substrate
how does hexokinase prevent hydrolysis of ATP
substrate binds with induced fit changing enzyme into active conformation
what is one reason enzymes are so large
have binding energy to pay for entropy reduciton
