Thermodynamics and Metabolism

• _____________change () is a measure of the _______________ _______________ from a reaction

• = change in ______________

• ___ = change in ______________

A. Thermodynamic Quantities

• Both entropy and enthalpy contribute to G

(T = degrees Kelvin)

____ = reaction is _____________ in the direction written

______ = reaction is ______________

_________ reaction is at ___________

Relationship among energy, enthalpy and entropy

The Standard State (Go) 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 Go’ = -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)

Eo’ = 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 (E) 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