Metabolism I Flashcards
What is an exergonic reaction?
a spontaneous, favourable rxn.
- moves forward
- ΔG<0
What is an endergonic reaction?
a non-spontaneous, unfavourable rxn.
- moves backward
- ΔG>0
Definition of equilibrium
no net change in the amount of reactants or products, ΔG=0
ΔG = ?
- G(final)-G(initial)
or - -nFΔE
How do you determine ΔG’*?
By measuring concentrations of reactants and products at equilibrium when the is no net change
What is ΔG’*?
standard free-energy
ΔG’*=?
-RT ln([A][B]/[C][D])
or
-nFΔE’*
What is defined by the variable R?
The gas constant (8.315J/mol x k)
What is defined by variable T?
Absolute temperature
What happens to Ea of a reaction when an enzyme is added? Does the ΔG change?
Ea decreases but ΔG stays the same
What is ATP?
Adenosine triphosphate; cellular currency for energy, fuels most cellular activity, has high energy potential.
(3) phosphate groups+ribose+adenine
What gives ATP such a high potential energy?
The repellant focus of the negative charges on the phosphate groups
What is ATP coupling and how does it move unfavourable reactions forward?
ATP coupling: coupling ATP hydrolysis (favourable) with other unfavourable reactions to move them forward.
Hydrolysis of ATP to make ADP+Pi is very exergonic and it releases a lot of energy, this energy release is transferred to a substrate via phosphorylation
What is Keq?
The equilibrium constant for reaction
Keq=?
Keq=[products sum]/[reactants sum]
- excludes water as a product or reactant
- ex. for A+H2OB+C Keq=[B][C]/[A]
