Intro to Biochemical Rxns Flashcards
What is Kd in Thermodynamics?
Saturation point - point at which 50% of ligand is bound to substrate.
Also the dissociation constant
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
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)
Which of these rxns reach equilibrium?
a) ligand binding rxns
b) catalyzed rxns
c) both
a)
In catalyzed reactions, at very high substrate concentration, what happens to V?
It becomes Vmax
What does a substrate need to overcome to become a product?
Transition state
What is the function of enzymes (in regards to transition state)
Lower energy of transition state
Do enzymes affect the energy difference?
No, they just alter the kinetics of the rxn
What do you look at to investigate effect of inhibitor of kinetics?
Vmax and Km
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
Does [S] affect Vmax? Why or why not?
No, because Vmax is dependent on the enzyme concentration
Temperature, post translation modifications and enzyme mutations affect
a) Vmax
b) rate
c) Km
d) all of the above
all of the above
The lower the Km, the _______ the affinity
higher
What is the effect of irreversible inhibitors on:
[E]
Vmax
Km
lowers [E] –>
Lowers Vmax
Does not affect Km (still same affinity)
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
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
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
Which of these is not an irreversible inhibitor?
a) Statins
b) Lead
c) HIV protease inhibitors
d) ibuprofen
e) penicillin
d - competitive inhibitor
Describe the mechanism of action of ibuprofen
Competitively inhibits COX enzymes that convert arachidonic acid to prostaglandin involved in inflammatory response and pain
Describe the mechanism of action of statins
Irreversible inhibitor of NZs involved in cholesterol biosynth
Describe the mechanism of action of lead
Irreversible inhibitor of many NZs, binds to SH group on proteins
Describe the mechanism of action of HIV protease inhibitors
Irreversible inhibitor, prevents cleaving of polypeptide into virus proteins
Describe the mechanism of action of penicillin
Irreversible inhibitor of NZ involved in cell wall synthesis in bacteria
