2.2 Enzyme equilibria

Question 1

Explain what is a reaction quotient, its equation

Answer 1

Reaction quotient (Q) - a ratio of reactant and product quantities for a specific reaction at a specific time

Question 2

Explain reaction quotient values

Answer 2

Question 3

Explain what is an equilibrium constant, its equation

Answer 3

Equilibrium constant (K) - a reaction quotient at equilibrium (dynamic equilibrium)

Question 4

Explain equilibrium quotient values

Answer 4

Question 5

Compare reaction quotient vs equilibrium constant

Answer 5

Reaction quotient - not at equilibrium
Equilibrium constant - at dynamic equilibrium (reversible reactions happen at the same time)

Question 6

Which equation allows to link equilibrium constant to Gibbs free E

Answer 6

At DYNAMIC EQUILIBRIUM

Question 7

Which equation allows to link reaction quotient to Gibbs free E

Answer 7

NOT at dynamic equilibrium

Question 8

Which equation allows to link temperature to Gibbs free E at dynamic equilibrium / not at equilibrium

Answer 8

ΔG = ΔG°+RTln(Q)
ΔG = -RTln(K)

Question 9

Van’t Hoff equation: temperature and equilibrium constant

Answer 9

Question 10

What is the Van Hoff plot, what can be calculated from it?

Answer 10

Question 11

What are the association and dissociation constants?

Answer 11

Ka - measures how tightly molecules bind (ex: enzymes and ligands)
Kd - measures how easily molecules disassemble (ex: enzyme and ligands) - more commonly used in biochem

The lower Kd - the tighter the binding - harder to disassemble

Question 12

How to define the fraction of total ligand bound sites (θ)

Answer 12

[P]total = [P] + [P-L]
θ = [P-L] / ([P] + [P-L]) fraction of bound proteins
Kd = [P][L] / [P-L]

Question 13

Kd = conc [L] where θ = 0.5 plot

Answer 13

Rectangular hyperbola -> further transform into linear by 1/θ to derive info

Question 14

1/θ vs 1/[L] graph

Answer 14