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]
what does coupling ATP hydrolysis do the the Keq of unfavourable reactions?
It raises it
- ex. for ATP coupling with glucose-6-phosphate synthesis raises the Keq of glucose-6-phosphate by a factor of ~2x10^5
What is a REDOX reaction?
reduction-oxidation reaction; chemical rxns involving electron transfer
ex. A(red)+B(ox)A(ox)+B(red)
What happens to an atom/molecule the it is oxidized?
It loses an electron
What happens to an atom/molecule when it is reduced?
It gains an electron
The more ___ a C atom is, the more free energy is released the it is oxidized
Reduced
Where is potential energy stored?
Within bonds
How is H+ involved in REDOX reactions?
They usually accompany electrons, reduction adds H+ andoxlidation revokes them
What is the function of FADH2?
FADH2= flavin adenine dinucleotide
It is an electron carrier
AH2+FAD–>A+FADH2, two elections transfer along with two H+ ions to allow AH2 to oxidize while FAD is reduced, pairs with catabolic reactions
What is the function of NADH?
NADH= nicotinamide adenine dinucleotide
It is an electron carrier
BH2+NAD+–>B+NADH+H+, two electrons transfer along with two H+ ions to allow BH2 to oxidize while NAD+ is reduced, pairs with catabolic reactions
What does reduction potential measure?
The flow of electrons, measured in V
What is E’*?
Standard reduction potential at pH=7.0
ΔE’*=?
E’(acceptor)-E’(donor)
What is the variable F?
Farraday’s constant, 96.5kJ/V x mol
What is the variable n?
Number of electrons lost
Reducing agent is …
The molecule/atom that becomes oxidized/reduces the other compound
Oxidizing agent is …
The molecule/atom that becomes reduced/oxidizes the other compound
How does malate+NAD+–>oxaloacetate+NADH+H+ proceed forwards even though it has a positive ΔG’* value?
- The concentration of NADH is greater than that of NAD+
- oxaloacetate is quickly removed so it always has a low concentration
Both of these reason favour forward reactions
What is the Michaelis-Menten Equation?
V0=(Vmax[S])/(Km+[S])
