Intro to Biochemical Rxns Flashcards Preview

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Flashcards in Intro to Biochemical Rxns Deck (23)
1

What is Kd in Thermodynamics?

Saturation point - point at which 50% of ligand is bound to substrate.
Also the dissociation constant

2

In a ligand binding reaction, will changing [S] may have one of these results:
a) change the shape of the curve
b) shift the curve
c) both

b
will not change shape because not changing affinity

3

In a ligand binding rxn, if the conformation of S changes, it may have one of these results:
a) change the shape of the curve
b) shift the curve
c) both

c)

4

Which of these rxns reach equilibrium?
a) ligand binding rxns
b) catalyzed rxns
c) both

a)

5

In catalyzed reactions, at very high substrate concentration, what happens to V?

It becomes Vmax

6

What does a substrate need to overcome to become a product?

Transition state

7

What is the function of enzymes (in regards to transition state)

Lower energy of transition state

8

Do enzymes affect the energy difference?

No, they just alter the kinetics of the rxn

9

What do you look at to investigate effect of inhibitor of kinetics?

Vmax and Km

10

Enzyme concentration does NOT affect which of the following:
a) rate of reaction
b) Km
c) shape of curve
d) position of curve
e) more than one of the above

e) a + d

11

Does [S] affect Vmax? Why or why not?

No, because Vmax is dependent on the enzyme concentration

12

Temperature, post translation modifications and enzyme mutations affect

a) Vmax
b) rate
c) Km
d) all of the above

all of the above

13

The lower the Km, the _______ the affinity

higher

14

What is the effect of irreversible inhibitors on:
[E]
Vmax
Km

lowers [E] -->
Lowers Vmax
Does not affect Km (still same affinity)

15

What is the effect of competitive inhibitors on:
[E]
Vmax
Km

[E] does not change (rxn reversible)
Vmax is unaffected
Going to need more substrate to compete with inhibitor (enzyme likes inhibitor too so lower affinity for substrate)
--> Km increases

16

What is the effect of uncompetitive inhibitors on:
(forms ESI)
[E]
Vmax
Km

Enzyme concentration unaffected
Vmax is decreased because when it forms ESI, the ESI is slower at forming product E+I+P
Km is decreased because inhibitor enhances binding affinity of E to S

17

What is the effect of noncompetitive inhibitors on:
(forms EI and ESI)
[E]
Vmax
Km

Inhibitor does not bind to active site, but changes the substrate so Vmax decreases because slows rate of rxn

[E] unaffected
Vmax dec
Km unaffected

18

Which of these is not an irreversible inhibitor?
a) Statins
b) Lead
c) HIV protease inhibitors
d) ibuprofen
e) penicillin

d - competitive inhibitor

19

Describe the mechanism of action of ibuprofen

Competitively inhibits COX enzymes that convert arachidonic acid to prostaglandin involved in inflammatory response and pain

20

Describe the mechanism of action of statins

Irreversible inhibitor of NZs involved in cholesterol biosynth

21

Describe the mechanism of action of lead

Irreversible inhibitor of many NZs, binds to SH group on proteins

22

Describe the mechanism of action of HIV protease inhibitors

Irreversible inhibitor, prevents cleaving of polypeptide into virus proteins

23

Describe the mechanism of action of penicillin

Irreversible inhibitor of NZ involved in cell wall synthesis in bacteria