Lt 13 Regulation Flashcards
How long does allosteric enzyme regulation take?
Seconds
How long does covalent modification/phosphorylation take?
Minutes
How long does hormonal enzyme regulation take?
Hours/Days
What three main sites are on a allosteric enzyme?
Active site, allosteric inhibition, allosteric activation
What do allosteric activators/inhibitors do? Are they big or small?
Big. Alter active site shape resulting in activity change
Do all allosteric enzymes have quaternary structure?
Yes
What is the name of the shape of this curve?
At what point does the allosteric enzyme bind?
Is increasing [S] having an effect?
Sigmoidal
At the sharp increase
Not until symmetry point
What are the two forms an allosteric enzyme exists in?
Which does the substrate have affinity for?
Tense (T) and Relaxed (R)
Relaxed
Which does the equilibrium favour T or R?
What causes the equilibrium to shift?
Favours T, but binding of substrate causes this to shift from T to R at same time
Do allosteric inhibitors bind on R or T form?
Which way does this cause the equilibrium to swing
T form
Pushes it more to T making it hard for substrate to bind
Where do allosteric activators bind? T or R?
What effect does this have on equilibrium?
Allosteric site on R form
More R available for S to bind
What are 3 advantages of allosteric control?
Selective (only specific enzymes pathways are controlled)
Flexible (adapts quickly to changing needs of the cell)
Sensitive (Vo can change massively when substrate, activator or inhibitor conc change)
What does the regulation of enzyme activity by covalent modification usually involve?
Addition or removal of phosphate groups
What happens when phosphorylation occurs
Use ATP as phosphate donor
What happens when dephosphorylation occurs?
Removal of phosphate group
