Intro to Biochemical Rxns Flashcards Preview

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Flashcards in Intro to Biochemical Rxns Deck (23)
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1
Q

What is Kd in Thermodynamics?

A

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

2
Q

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

A

b

will not change shape because not changing affinity

3
Q

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

A

c)

4
Q

Which of these rxns reach equilibrium?

a) ligand binding rxns
b) catalyzed rxns
c) both

A

a)

5
Q

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

A

It becomes Vmax

6
Q

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

A

Transition state

7
Q

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

A

Lower energy of transition state

8
Q

Do enzymes affect the energy difference?

A

No, they just alter the kinetics of the rxn

9
Q

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

A

Vmax and Km

10
Q

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

A

e) a + d

11
Q

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

A

No, because Vmax is dependent on the enzyme concentration

12
Q

Temperature, post translation modifications and enzyme mutations affect

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

A

all of the above

13
Q

The lower the Km, the _______ the affinity

A

higher

14
Q

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

A

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

15
Q

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

A

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

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

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
Q

Which of these is not an irreversible inhibitor?

a) Statins
b) Lead
c) HIV protease inhibitors
d) ibuprofen
e) penicillin

A

d - competitive inhibitor

19
Q

Describe the mechanism of action of ibuprofen

A

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

20
Q

Describe the mechanism of action of statins

A

Irreversible inhibitor of NZs involved in cholesterol biosynth

21
Q

Describe the mechanism of action of lead

A

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

22
Q

Describe the mechanism of action of HIV protease inhibitors

A

Irreversible inhibitor, prevents cleaving of polypeptide into virus proteins

23
Q

Describe the mechanism of action of penicillin

A

Irreversible inhibitor of NZ involved in cell wall synthesis in bacteria