APK 2105C Lecture 10: Cell Metabolism Part 3
23 May 2018
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Department
Course
Professor
Chapter 3, Part 3
Cell Metabolism
• Equilibrium = reactant is converted to product at the same rate that the product is
converted to the reactant
o Energy is equal on both sides of the equation
o deltaE = 0
o [reactant] does NOT = [product]
o If the E difference is large between the reactants and products—conc difference
at equilibrium will also be large
▪ If the energy per mole of the reactants (2
kcal/mol) is greater than that of the products
(1 kcal/mole), at equilibrium there will be
greater conc of products
• The law of mass action
o An increase in [reactants] relative to [products] tends
to push a rxn forward
▪ Add more reactant, get more product
o An increase in [products] relative to [reactants] tends to push a rxn in reverse
▪ Get more product, reverse to more reactants
o K = [product] / [reactant]
▪ Example: if K = 2 is that endergonic or exergonic?
• If K = 2, then the conc of product = 2 and conc of reactant = 1
• Concentration of product > concentration of reactant
• Endergonic reaction because it would need energy input to
proceed to high product concentration
• Rxn would want to go backwards
• Activation energy barrier = higher in energy than reactants or products,
needs to be overcome for rxn to proceed
o Forward activation energy = energy need to overcome
activation energy barrier
o Reverse activation energy = energy needed to push rxn
in reverse
o Explains why exergonic rxns proceed spontaneously
▪ Going from high amount of energy to products
with low energy is easier—don’t have to add as
much energy—this energy can come from
molecules combining
o Transition state = reactants coming together and leaving changed into products
▪ Have to have enough energy to overcome activation energy barrier
• Reaction rates
o How fast are reactants consumed and products made?
o Physiologically significant
▪ Rxn rates must match cellular demands at any given moment
▪ Have to be able to provide enough energy immediately to be able to do
work
o Factors affecting rxn rate
▪ [reactant] and [product]
• Increase in [reactants] = faster rxn rate of forward rxn
o Does not affect rxn rate of reverse rxn
