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S 2007 BIOC 3406. 01-18-07. Principles of Bioenergetics. Management of energy is a characteristic of living systems. ♫♫Stayin’ Alive… Growth Reproduction. Life uses energy to…. Synthesize the molecules of life Produce Motion Heat Light Create gradients (establish potential fields)

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management of energy is a characteristic of living systems
Management of energy is a characteristic of living systems
  • ♫♫Stayin’ Alive…
  • Growth
  • Reproduction
life uses energy to
Life uses energy to…
  • Synthesize the molecules of life
  • Produce
    • Motion
    • Heat
    • Light
  • Create gradients (establish potential fields)
    • Concentration
      • Chemical
      • Hydrogen ion
    • Electrical potential
life obtains energy
Life obtains energy
  • From environmental heat?
  • From light?
  • - From chemical fuel
    • Respiration
thermodynamics
Thermodynamics
  • Energy – “The capacity to do work”

q, heat; disorganized energy. Can only do work by passing from high to low temperature

w, work; organized energy. Can be

pressure-volume work

electrical work

concentration work

free energy
“Free” energy
  • Essentially from the sun
    • Spectrum of very hot body
    • Energy density of cool body
  • Direct from sun
    • Photosynthetic cells
    • Heterotrophic cells
g free energy
G, “Free” energy
  • Process converts reagents A into products B
  • G is the energy difference in the products B in their standard states and the reagents A in their standard states
thermodynamics9
Thermodynamics
  • E = q + w

E is the change in internal energy (kinetic + potential energy)

  • H = E + PV ( at constant P)

H is the Enthalpy; the “heat of reaction” at constant T and P

  • G = H - TS (constant T, P

G is the change in Gibbs Free energy

systems
Systems
  • Isolated
    • No interaction with the rest of the universe
  • Closed
    • Exchanges energy with the rest of the universe
  • Open
    • Exchanges matter as well as energy with the rest of the universe
processes
Processes

A  B

In a real process, S is positive (2nd Law)

(S of universe)

G’s sign gives the character of the process

G = 0 A, B already in equilibrium

G > 0 A increases, B decreases

G < 0 B increases, A decreases

processes12
Processes
  • If A↔B, at equil, then if start with

A ↔ B,

B will↑, A will↓

  • If A↔ B, at equil, then if start with

A ↔ B,

A will↑, B will↓

equilibrium
Equilibrium
  • When A and B are in the same medium, there is continuous interconversion

A  B and B  A

If forward and backward rates are equal, system is in equilibrium

Ratio of backward and forward rates = K, the equilibrium constant

K is also numerically equal to the ratio of the products to the reagents at equilibrium

q mass action ratio
Q “Mass Action Ratio”
  • For any mixture of A and B, Q is the ratio of the products and reactants at any instant
    • If product of product concentrations > product of reactant concentrations, Q < 1
    • If product of reactant concentrations > product of product concentrations, Q > 1
    • If product of product concentrations = product of reactant concentrations, Q = 1
meaning of superscripts
Meaning of Superscripts
  • “°”
    • Standard state: Reagents, products at 1M, pH 0 (H+ at 1M) (If acid-base reaction)
  • “’”
    • Biochemical standard state: pH 7, Mg2+ ~1 mM, aqueous solvent
slide16
G, G’°
  • G – A driving force
    • For conditions A, B (actual concentrations)
  • G’° – A driving force
    • For conditions A’°, B’°
slide17
G, G’°
  • G° = - RTln K =-RTln (std forward rate)/(std backward rate)
  • G = -RTln Q =-RTln (actual forward rate)/(actual backward rate)
problems
Problems
  • p 518, 2-5
slide19

K

270

890

Glucose 6-phosphate + H2O  glucose + Pi

ATP + glucose  glucose 6-phosphate

G = G1 + G2

= - RTln K = - RTln K1 - RTln K2

= - RT(ln K1 + ln K2)

= - RT (ln K1K2)

= - RTln K

phosphoryl group transfer
Phosphoryl Group Transfer
  • Hydrolysis of anhydrides, esters creates an acid or other active compound, drives equilibrium to the right
  • Hydrolysis of ATP
    • -30.5 kJ/mol
  • PEP +H2O  pyruvate
    • -61.9 kJ/mol!
  • 1,3-bisphosphoglycerate  Pi + 3-PG
    • -49.3 kJ/mol
  • Acetyl coenzyme A + H2O  CoASH
    • -31.4 kJ/mol