Biochemistry E2 Flashcards
What is the fractional saturation of binding?
Y= [S] ÷ (KD + [S])
The concentration of bound ligand divided by the total amount of protein/enzyme
What is KD
The dissociation constant or the [S] at half the saturation
What is KD related to when the protein is enzymatic/catalytic?
KD=KM
In a Sctchard plot graph, when n=1,
Slope
x-intercept
y-intercept
Slope: -1/KD
x-intercept = [E]T
y-intercept = 1/KD
In a Sctchard plot graph, when n>1,
Slope
x-intercept
y-intercept
Slope: -1/KD
x-intercept = n
y-intercept = n/KD
What is the Hill Equation?
Log(ø ÷ (1-ø)) = Log (1/KD) + nLog[S]
What type of graphs are Hill Plots usually?
Sigmoidal
What does the slope of the Hill plot tell us?
Slope= n
n>1 = Positive cooperativity
0
What is the y-intercept of the Hill plot?
log(1/KD) = log(1/Km)
Michaelis-Menten Kinetics follow what order of enzymes?
First Order Enzymes
What does the graph of Zero-order kinetics look like?
If [S] vs time is linear, the reaction is 0-order
v=k
What does the graph of First-order kinetics look like?
If ln[S] vs time is linear, the reaction is 1st order
v=k[S]
What does the graph of Second-order kinetics look like?
If 1/[S] vs time is linear, the reaction is 2nd order
v=k[S][S] or v=k[S1][S2]
What is the initial reaction rate equation?
V0 = Vmax • [S] ÷ ([S] + Ks)
What are the three assumptions for Michaelis-Menten Kinetics?
- Binding of the substrate to the enzyme is at equilibrium
(Ks = K-1/K1) - Since we are measuring initial rate, not enough product is present for the reverse reaction to occur
(Secon step is irreversible) - Stead State Assumption
What is the steady state assumption?
- When [S] is very large, ∆[S] = 0
- Formation of E•S complex occurs at the same rate that its loss either by dissociation or by product formation
Define Km
Michaelis Menten constant
When [S] where half the active sites are full
OR
When [S] where the reaction is half maximal
What is the equation for the Michaelis Menten Kinetics?
V0= Vmax • [S] ÷ ([S]+Km)
Define Vmax
How fast the reaction can take place
Vmax = Kcat[E]
Kcat is the same as
K2
Movement from E•S complex to E•P complex
(Changing Substrate to Product)
What happens when [S]<
V0 = (vmax÷Km) * [S]
Less than half the binding sites are occupied
What happens when [S]=Km
V0 = Vmax/2
Half the binding sites are occupied
What happens when [S]»Km
V0 = Vmax
All the binding sites are occupied
What is the specificity constant?
Kcat ÷ Km = (Kcat ÷ (K-1 +Kcat)) •K1
Used to determine catalytic efficiency
Measures what happens when to E•S complex
