chapter 3 section 3

Question 1

What concentrations are used in the ΔG equation for cellular reactions?

Answer 1

The actual cellular concentrations of the reactants and products, not standard-state values.

Question 2

Why is the cellular ΔG different from ΔG°′?

Answer 2

The cell is not at equilibrium nor at standard state; cellular ΔG reflects how far the system is from equilibrium.

Question 3

Write the equation to calculate the actual free energy change ΔG for the reaction.

Answer 3

ΔG = ΔG°′ + RT ln([F6P]/[G6P])

Question 4

What equation relates ΔG°′ to the equilibrium constant?

Answer 4

ΔG°′ = -RT ln(K_eq)

Question 5

How is the cellular free energy change (ΔG) calculated?

Answer 5

ΔG = ΔG°′ + RT ln([G3P]/[DHAP])

Question 6

What are the three conditions under which a biochemical reaction can be considered?

Answer 6

Standard state, equilibrium, and cellular conditions.

Question 7

What is the standard-state free energy change (ΔG°′)?

Answer 7

ΔG°′ is the free energy change when all reactants and products are at 1 M concentration (and [H⁺] = 10⁻⁷ M), serving as a reference point.

Question 8

Why is standard state rarely found in living organisms?

Answer 8

Because actual cellular concentrations of metabolites are usually far from 1 M, so standard-state conditions are mostly theoretical.

Question 9

What happens if a reaction at standard state is left alone?

Answer 9

It will proceed toward equilibrium, where ΔG = 0 and the ratio of products to reactants is set by the equilibrium constant.

Question 10

How does ΔG°′ relate to equilibrium?

Answer 10

ΔG°′ = -RT ln(K_eq), linking standard-state free energy to the equilibrium constant.

Question 11

For the DHAP ⇌ G3P reaction, what does a positive ΔG°′ indicate?

Answer 11

That at equilibrium, [DHAP] > [G3P]; the reaction favors DHAP under standard-state conditions.

Question 12

What does the magnitude of ΔG°′ measure?

Answer 12

How far standard-state conditions are from equilibrium.