Thermodynamics and
Metabolism
A. Thermodynamic Quantities
• _____________change (___) is a
measure of the _______________
_______________ from a reaction
• ___ = change in ______________
• ___ = change in ______________
Relationship among energy,
enthalpy and entropy
• Both entropy and enthalpy contribute
to DG
(T = degrees Kelvin)
____ = reaction is _____________ in
the direction written
______ = reaction is ______________
_________ reaction is at ___________
The Standard State (DGo)
Conditions
• Reaction free-energy depends upon
conditions
• ________________ (_____) - defined
reference conditions
Standard Temperature = ______(25oC)
Standard Pressure = ______________
Standard Solute Concentration = _____
• ____________standard state = _____
Standard ____ concentration = _____
(________) rather than 1.0M (pH = 1.0)
B. Equilibrium Constants
and
Standard Free-Energy
Change
• For the reaction: _______________
• At equilibrium:
And _________________, so that:
C. Actual Free-Energy Change
Determines Spontaneity of
Cellular Reactions
• When a reaction is not at
equilibrium, the _______________
_____________________________
_____________________________
(the ratio)
• ____ = the _______________ ratio
Where
The Free Energy of ATP
• ___________________ of metabolic
fuels is largely _________________
______________________________
ATP is an “______________”compound
• A large amount of energy is released
in the hydrolysis of the
_______________________ of ATP
(and UTP, GTP, CTP)
• All nucleoside phosphates have
nearly equal standard free energies
of hydrolysis
Complexes between ______and ______
Why are phosphoanhydrides high energy
compounds?
(1) ____________________ among negatively
charged oxygens of phosphoanhydrides of
ATP
(2) ______________________ (ADP and Pi)
or (AMP and PPi) is better than solvation of
reactant ATP
(3) ______________________ than reactants
There are more delocalized electrons on
ADP, Pi or AMP, PPi than on ATP
The Metabolic Roles of ATP
• ___________________________________
___________________________________
• Reactions can be linked by a common
_____________________ (B-X) below
A-X + B
A + B-X
B-X + C
B + C-X
Glutamine synthesis requires ATP energy
Phosphoryl-Group Transfer
• ___________________________ - the ability
of a compound to ______________________
____________________________________
• Energy-rich or high-energy compounds have
group transfer potentials _________________
____________________________________
• Low-energy compounds have group transfer
potentials less than that of ATP
Production of ATP by Phosphoryl-Group
Transfer
• ___________________________________
___________________________________
to form ATP
• __________________________________
in ________________ pathways
• ___________________________________
___________________________________
Relative phosphoryl-group-transfer potentials
Transfer of phosphoryl group from PEP to ADP
• Phosphoenolpyruvate (PEP) (a glycolytic
intermediate) has a high P-group transfer
potential
• PEP can donate a P to ADP to form ATP
___________________: Energy-rich storage
molecules in animal muscle
• _______________ (PC) and _____________
(PA) are ________________________
• Have higher group-transfer potentials than
ATP
• Produced in muscle during times of ample
ATP
• _____________________ when needed via
creatine kinase reaction
Structures of PC and PA
__________-Group Transfer
• Transfer of the nucleotidyl group from ATP is
another common group-transfer reaction
• ___________________ requires transfer of
an ________moiety to acetate
• ___________________________________
___________________________________
Synthesis of acetyl CoA
_________ Have High Free Energies of Hydrolysis
• Thioesters are energy-rich compounds
• _____________ has a DGo’ = -31 kJ mol-1
_____________ Energy Can Produce GTP
__________________________________
from Biological Oxidations
• Amino acids, monosaccharides and lipids are
oxidized in the catabolic pathways
• ____________________________________
____________________________________
• ___________________________________
• Oxidation of one molecule must be coupled
with the reduction of another molecule
Ared + Box
Aox + Bred
Free-Energy Change Is Related to Reduction
Potential
• The ____________________ of a reducing
agent is a measure of its thermodynamic
________________
• The __________________ is the measured
__________________________________
• Reference half-cell reaction is for hydrogen:
2H+ + 2e-
H2
Diagram of an electrochemical cell
• Electrons flow through external circuit
from Zn electrode to the Cu electrode
Standard reduction potentials and free energy
• Relationship between standard free-energy
change and the standard reduction
potential:
n = # electrons transferred
F = Faraday constant (96.48 kJ V-1)
DEo’ = Eo’electron acceptor - Eo’electron donor
Actual reduction potentials (_____)
• Under biological conditions, reactants are not
present at standard concentrations of 1 M
• Actual reduction potential (DE) is __________
_________________ of reactants and products
__________________________________________
_______________________________________
• Most _______ formed in metabolic reactions
in aerobic cells is _____________________
___________________________________
• Energy _________________ from ADP, Pi
• Half-reaction for overall oxidation of NADH:
Methods for Studying Metabolism
• Add ______________ to tissues, cells, and
follow emergence of intermediates
• Use sensitive isotopic ______ (3H, 14C etc)
• Verify pathway steps in vitro by using
____________________ and substrates
• Use metabolic ____________ to identify
individual steps and sequence of enzymes
in a pathway