Uml Biochemistry Enzyme Catalysis Mechanisms

Front 1

The enzyme must stabilize the EX‡ transition state more than it stabilizes _______.

Back 1

ES
(energy barrier between ES and EX‡ must be smaller than the barrier between S and X‡)

Front 2

Tighter S binding results in ________ ES energy, expanding the activation energy barrier & thus ____________ rxn rate

Back 2

lowered ; lowering

Front 3

Substrates typically lose waters of hydration (--generally, charged groups are more stable in hydrated form —ΔHsolv) in the formation of the ES complex.
___________ (of charged groups) raises the energy of the ES complex, making it more reactive.

Back 3

Desolvation

Front 4

Charged groups may be forced to interact with similarly charged residues, resulting in _______________.
If such charge repulsion is relieved in the course of the reaction, (the first answer) can result in a rate ___________.

Back 4

electrostatic destabilization; increase

Front 5

You could use transition state analogs to _________________.

Back 5

study transition states

Front 6

TSA’s bind ________ strongly than S or other types of competitive inhibitors

Back 6

more

Front 7

Which is not an example of a transition state analog?
a. proline racemace
b. Pyrrole-2-carboxylate
c. Δ-1-pyrroline-2-carboxylate
d. proline dehydroxinase
e. Phosphoglycolohydroxamate
f. hydrated from of purine ribonucleoside

Back 7

d.

Front 8

Covalent (aka nucleophillic) catalysis:
Enzyme and substrate become linked in a __________ covalent bond at one or more points in the reaction pathway.
Covalent bond formation provides the chemistry that speeds the reaction.

Back 8

transient

Front 9

In _______________ catalysis, H+ or OH- concentration affects the reaction rate, kobs is pH-dependent, but buffers (which accept or donate H+/OH-) have no effect.

Back 9

specific acid-base

Front 10

In _____________ catalysis, an ionizable buffer may donate or accept a proton in the transition state, kobs is dependent on buffer concentration.

Back 10

general acid - base

Front 11

In low-barrier H bond catalysis, as the O-O distance _________, the hydrogen bond becomes stronger, and the bond order of the weakest interaction increases.

Back 11

decreases

Front 12

In Metal-ion catalysis, Ions such as ______and ______ may be either structural or catalytic (“loosely bound”)

Back 12

Mg2+ , Zn2+

Front 13

Metal ions participate in the catalytic process in three major ways. Which of the following is not true?:

1. By binding to substrates to orient them properly for reaction.
2. By mediating oxidation–reduction reactions through reversible changes in the metal ion's oxidation state.
3. By providing a covalent linkage site for stabilization
4. By electrostatically stabilizing or shielding negative charges.
5. All of these are true

Back 13

3.

Front 14

Serine proteases are homologous, but locations of the three crucial residues differ somewhat. What are the 3 crucial residues?

Back 14

Ser, His, Asp