Bioenergetics

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Bioenergetics

• The Flow of Energy in the Cell

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Living Versus Nonliving

• Living cells/organisms maintain order.

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Life Has 4 Essential
Requirements

• Molecules that provide basic building blocks
• Chemical catalysts (enzymes)
• Information that guide activities
• Energy to drive reactions and processes
  necessary for life

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Nonliving Versus Living
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Maintenance of Order

• How do cells maintain or create order?

Energy
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Energy

• Capacity to cause change capacity to do work
  the ability to rearrange matter.
• Kinetic energy of motion
• Examples
• Heat (random movement of molecules)
• Light (movement of photons)
• Potential stored energy or energy of position
• Example
• Chemical energy (energy due to structure)

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Flow of Energy through Biosphere
Against concentration, electrical gradient
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Ultimate Fate of All Energy.

• Is to become randomized in the biosphere as
  increased entropy.
• Energy flows from nuclear fusion of sun to
  eventual sink, the entropy of the universe.
• Every process of reaction that occurs in the
  universe leads to greater entropy.

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Energetics

• Is there a great divide between the living and
  the nonliving?
• No, according to Erwin Schrödinger
• Both obey same laws of chemistry physics
• Thermodynamics laws and principles that govern
  flow of energy.

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Closed System
System Surroundings Universe
surroundings
system
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Open System

• Energy is transferred to or from the surroundings.

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1st Law of Thermodynamics
The law of conservation of energy

• Energy can be transferred or transformed but
  cannot be created or destroyed.

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1st Law of Thermodynamics

• During any reaction the total amount of E that
  leaves the system the E that enters the system
  minus E that is stored within system
• ?E difference in internal energy of the system
  before the reaction (E1) and after the reaction
  (E2)

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Meaning of ?E

• ?E E2 E1
• ?E E products E reactants
• Change in enthalpy (heat content)
• H E PV
• ?H ?E ?(PV) PV 0
• ?H H products H reactants
• ?H Neg (endothermic), Positive (exothermic)

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2nd Law of Thermodynamics

• Every energy transfer or transformation increases
  entropy of the universe.

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Does life violate 2nd law?

• NO!
• Life forms are open systems.
• Energy from complex molecules ? simple molecules
  used to maintain order.
• Heat generated ? entropy of surroundings.

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DG (Change in Free Energy)

• DG is convenient way to measure the amount of
  disorder created in the universe when a chemical
  reaction takes place.

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Energy Profiles
DG Gproducts - Greactants
Exergonic Reaction (Spontaneous)
Endergonic Reaction (Non-spontaneous)
transition state
transition state
Free energy ?
EA
EA
products
DG gt 0
reactants
DG lt 0
products
reactants
Progress of reaction ?
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What if DG 0?

• Reaction has reached chemical equilibrium.

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Relationship Between Keq DG
(DG 0)
Keq
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DG

• Free energy change under standard conditions
• indicates pH 7.0
• indicates
• products reactants 1.0M (except water)
• Temperature 25C 298K
• Pressure 1 atmosphere
• Useful way to compare reactions.

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DG

• Under standards conditions, all of these
  reactions will proceed to right.

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Relating DG to DG
R 1.987 cal/molK T temperature in Kelvin