Enzyme Mechanisms

Question 1

what do catalysts not affect

Answer 1

free energy change of a reaction

Question 2

catalysts ______ alter the equilibrium concentratiosn of products and reactants

Answer 2

do not

Question 3

enzymes typically accelerate reactions by factors

Answer 3

greater than 10^6

Question 4

reasons why enzymes are amazing protein catalysts

Answer 4

1. enzymes have amazing catalytic power
2. enzymes have exquisite specificity
3. enzymes operate under mild biological conditions

Question 5

cofactor

Answer 5

any non-amino acid chemical component of an enzyme

Question 6

coenzyme

Answer 6

a complex organic or metalloorganic molecule that binds non covalently

Question 7

prosthetic group

Answer 7

tightly bound or covalently attached cofactor (like the heme in hemoglobin)

Question 8

polypeptide component

Answer 8

apoenzyme

Question 9

polypeptide component with cofactor attached

Answer 9

holoenzyme

Question 10

do cofactors change by the reaction?

Answer 10

no, if they did change they would be substrates

Question 11

what do enzymes do for ts and free energy

Answer 11

reduce free energy needed to achieve transition state

Question 12

at the end of the reaction, what is the free energy state of catalyzed and uncatalyzed

Answer 12

da same

Question 13

enzymes accelerate

Answer 13

both the forward and reverse reactions

Question 14

what is reaction rate proportional to

Answer 14

concentration of x double dagger

Question 15

what is x double dagger

Answer 15

conformation of substrate that must be achieved in order for chemistry to work

Question 16

catalysts do what to the Ea of rxns which increases what

Answer 16

catalysts lower the activation energy of reactions which increases concentration of x double dagger

Question 17

reaction energy reduction can be

Answer 17

60 - 100 kj/mol

Question 18

_____ - fold shift in equilibrium for each ______ kj/mol free energy change

Answer 18

10 fold, 6

Question 19

E+S transient blip why

Answer 19

increase in delta g becayse enzyme bingind to substrate decreases entropy

Question 20

ES transient blip why

Answer 20

decrease in delta g because enthalpy decreases

Question 21

EP transient blip why

Answer 21

increase in delta g because breaking bonds increases free energy bc enthalpy increases bc h bonds satisfied with water instead of protein itself

Question 22

electrostatic catalysis

Answer 22

preferential binding to the transition state through complementary noncovalent interactions

Question 23

which component does electrostatic catalysis stabilize

Answer 23

stabilize enthalpic component

Question 24

entropy reduction

Answer 24

binding of substrates in a way that optimizes their proxumuty, orientation, and conformation for reaction

Question 25

what component foes entropy reduction stabilize

Answer 25

entropic

Question 26

induced fit

Answer 26

change in conformaiton of the active site opon substrate binding renders the enzyme catalytically active (gives substrate specificity)

Question 27

transition state stabilization catlytic strategies

Answer 27

1. electrostatic catalysis 2. entropy reduction 3. induced fit

Question 28

metal ion catalysis

Answer 28

yse of metal ion cofactors, often to promote the formation of OH-

Question 29

covalent catalysis

Answer 29

alter reaction pathweay to include intermediates with covalent bonds not in reactants or products

Question 30

general acid-base catalysis (GABC)

Answer 30

use of functional groups that alternately act as acuds and bases, often for reactions incoloving H+ transfer

Question 31

which major catalystic strategies are new intermediates in reaction pathway

Answer 31

metal ion catalysis covalent catalysis general acid-base catalysis

Question 32

which major catalytic strategy is very common

Answer 32

general acid-base catalysis

Question 33

why does enzymes enforcing proper positioning lower activation energy

Answer 33

less entropy reduction required to reach x double dagger

Question 34

what is the cost for bringing two molecules into proximity to form one molecule

Answer 34

entropy

Question 35

how does enzyme binding pay for the ____ cost?

Answer 35

entropy cost, using multiple noncovalent interactions between the enzyme and substrate

Question 36

how does hexokinase prevent hydrolysis of ATP

Answer 36

substrate binds with induced fit changing enzyme into active conformation

Question 37

what is one reason enzymes are so large

Answer 37

have binding energy to pay for entropy reduciton