Application to Enzymes

Question 1

Rate vs rate enhancement

Answer 1

Rate is the speed at which something is going.
Rate enhancement is how much faster that thing can go.
Enzymes:
Something is too slow to do under phys. conditions, so it can be enhanced to make it go faster.

Question 2

∆∆G°(++)

Answer 2

• Related to rate enhancement… Change in the change in the free energy that you need to reach the transition state.
• (Difference between free energy required for noncatalyzed rxn vs catalyzed rxn to achieve TS)
• overcome by the formation of noncovalent bonds

Question 3

Governor

Answer 3

stop the rxn from going over the fastest speed (diffusion rate)

Question 4

Why do enzymes increase forward and reverse rates equally?

Answer 4

• to avoid affecting the K (equilibrium constant), which you cant do as a catalyst.
• ## whats present at equilibrium doe snot change

Question 5

K =

Answer 5

L = k1 / k-1
ratio of the forward and reverse rate constants….

Question 6

∆H when there is binding tightly of substrate to transition state

Answer 6

energy is released . compare the energy released to the noncatalyzed reaction.
∆H catalyzed is less than ∆H uncatalyzed, due to the release of energy

Question 7

∆S when there is binding tightly of substrate to TS

Answer 7

proximity and orientation favor TS which gives a less negative ∆S.
WHY?
- need productive collision to make product, right orientation = productive collision, CATALYSTS CAN BIND IN CORRECT ORIENTATION
- this correct orientation increases the reactivity of the molecules by making ∆S++ less negative.
- why? because correct orientation = productive collision = more places to put energy, as the reaction is more likely to happen.
- one of those places to put energy is the enzyme. When enzyme binds, there is a change in conf, which requires energy
- bringing them into proximity so that there is an increase in possibility of doing rxn, you get a wider choice of places you can put your energy
-

Question 8

rate determining step

Answer 8

not binding of substrate, but achieving TS

Question 9

Ways to offset TS

Answer 9

• make two smaller TS with an intermediate between them
• making an alternative pathway

Question 10

Why is stereospecificity important?

Answer 10

because enzymes are based on amino acids that are in their L form

Question 11

geometric specificity

Answer 11

must fit the substrate into the actual site.

Question 12

ES complex vs EP

Answer 12

before TS… after TS

Question 13

Energy of E + S vs ES & EP vs E + P tell us what?

Answer 13

there is binding energy that must be overcome to release the product , and some that will be released when you form the ES product.

Question 14

1st step

Answer 14

reversible, occurs faster than the second step
E + S <> ES

Question 15

2nd step

Answer 15

K2&raquo_space; K-2

Question 16

3rd step

Answer 16

k3&raquo_space; k2

Question 17

preferential TS binding PTSB

Answer 17

enzymes active site must bind TS the most favorable way (best), than it binds substrate for ∆G°++ cat > ∆G°++ non….. means TS will be smaller…
this will ENHANCE your rate.

Question 18

if you want to increase rate by 36 kj/mol what do u do

Answer 18

break 2 hydrogen bonds. Rate enhancement is 10^6

Question 19

What must binding energy overcome?

Answer 19

entropy penalty… if you dont pay it the rxn will be unfavorable.

Question 20

active site on enzyme

Answer 20

includes both binding and catalytic sites.