Thermodynamics of Metabolism Flashcards
What must be true for reactions to be easily reversed by changing the ratio of products to reactants?
The reaction must be a near-equilibrium reaction
What will happen when the concentration of reactants in a reaction is greater than the equilibrium concentration of reactants?
The reaction will move in the forward direction until equilibrium is attained.
What are the rates of near-equilibrium reactions regulated by?
The relative concentration of reactants to products
What types of reactions are most metabolic reactions?
Near-equilibrium reactions
What is the implication for highly exergonic metabolic reaction (delta G is much less than 0)?
The reaction is irreversible and goes to completion.
What effect does a highly exergonic reaction have on a pathway that it is a part of?
Confers directionality on the pathway (makes the entire pathway irreversible).
What does every metabolic pathway have that commits a pathway to completion?
A committed step (usually near the beginning of the pathway
What is required for the reverse reaction of a highly exergonic pathway?
A different pathway for at least one of the reaction steps (or the existence of independent interconversion routes).
What does the existence of independent interconversion routes for a forward reaction and its reverse reaction allow?
Independent control of the two processes
What type of control would be impossible without independent interconversion routes for a forward reaction pathway and its reverse reaction pathway?
Being able to shut off one reaction while turning on the other, depending on whether product or reactant is required.
What remains constant in a pathway?
The concentration of metabolites
What step in a reaction determines flux (the rate of flow)?
The RDS (the slowest step or steps)
What is true of the RDS of a reaction pathway?
Its delta G is negative and large, so it operates far from equilibrium.
Why is the delta G of the RDS large and negative?
Because the RDS is slow, its product is used in the next reaction before it can equilibrate back to the reactants of the previous step.
What is true of all near-equilibrium reactions that are downstream from an RDS?
They all have the same flux