Thermodynamic Principles

1
Thermodynamic Principles

• A Review

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Thermodynamics

• Energy and Its Effects on Matter

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Thermodynamic Principles

• Thermodynamics determines whether a physical
  process is possible (i.e. spontaneous)
• Themodynamics provides no information about the
  rate of a physical process

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Thermodynamic Systems

• Closed Physical Chemistry (Equilibrium)
• Open Biochemistry (Steady-State)

Inputs and Outputs
5
First and Second Laws of Thermodynamics

• First Law of Thermodynamics
• Energy is Conserved
• Second Law of Thermodynamics
• The Universe Tends Toward Maximum Disorder

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Consequences of Second Law of Thermodynamics

• Spontaneous processes proceed in directions that
  increase the overall disorder of the universe
• Increased order in a system requires decreased
  order of the surroundings

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Free Energy

• Indicator of Spontaneity

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Gibbs Free Energy (G)

• G H TS
• H Enthalpy (Heat Content)
• S Entropy (Disorder)
• A gt B
• ?G GB GA
• ?G ?H T?S

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Change in Gibbs Free Energy (?G)

• Exergonic spontaneous
• Endergonic requires input of free energy

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Change in Enthalpy (?H)

• Exothermic system releases heat
• Endothermic system gains heat

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Time Course of Reaction
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Transition State
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Thermodynamics of the Transition StateA B gt
P Q
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Accelerating Chemical Reactions(Heat)
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Accelerating Chemical Reactions(pH)
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Accelerating Chemical Reactions (Catalysis
Reduces ?G)
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Free Energy and Work

• Thermodynamics
• Kinetics

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Examples

• Hydrophobic Interactions
• Stability of ATP

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Chemical Equilibria
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Equilibrium Constants
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Standard Free Energy Changes(Standard State
Conventions)

• One Mole
• 25C
• 1 Atmosphere

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Standard State Conventions in Biochemistry

• H2O 1
• (actual value 55.5 M incorporated into Keq)
• H 107 M (pH 7)

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Coupled Reactions

• Additivity of Free Energy Changes

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Coupled Reactions