Bioenergetic

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Chapter 5

• Bioenergetic

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Energy

• Capacity to do work
• Ability to cause specific changes
• 6 categories of change
• Synthetic
• Mechanical
• Concentration
• Electrical
• Generation of heat
• Generation of light

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Types of Change
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Synthetic Work

• Biosynthesis is the formation of new bonds
• Create new molecules for growing cell
• Also must maintain structures in the cell
• Energy needed to make energy rich organic
  molecules from subunits active subunits

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Mechanical Work

• Physical change in position or orientation of
  cell flagella or cilium to move organisms
• Muscle contraction
• Separate chromosomes
• Cytoplasmic streaming
• Ribosomes moving on mRNA

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Concentration Work

• Move molecules or ions against a gradient
• Increase the concentration in cell or remove
  cellular waste
• Maintaining Na/K concentration in the cell

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Electrical Work

• Specialized concentration work
• Ions transported across membrane, establishes an
  electrical potential across the membrane
• ATP generation in cellular respiration
• Photosynthesis
• Nerve impulses
• Uses 2/3 of the total energy in an organism

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Heat

• Major use of energy in animals that regulate
  their body temperature
• Takes about 2/3 of total energy
• Create heat when the ion transport is happening

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Bioluminescence

• Light production
• Specialized kind of energy

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Sunshine Ultimate Energy Source

• Energy comes from the sun or organic food
  molecules
• 2 types of organisms
• Phototrophs capture light by photosynthetic
  pigments
• Store energy as organic molecule
• Can also act as chemotrophs
• Chemotrophs energy is stored in chemical bonds
• Fermentation partial breakdown of organic
  molecules
• Cellular respiration electrons move from
  chemical bonds to O2
• Aerobic is when O2 is final electron acceptor
• Anaerobic is when no O2 is present

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Flow of Energy in Biosphere
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Bioenergentic

• Applied thermodynamics energy flow
• Heat, other forms of energy, conversions from 1
  form to another
• System part of a universe we want to study
• Open system shares energy with surroundings
• Closed system cannot take in energy or release
  energy to the surroundings
• Surrounding everything else

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Energy Exchange

• Between system and surroundings
• As heat hotter to colder, not useful to cells
• As work drive any process other than heat flow
• Energy changes expressed in calories amount of
  energy required to warm 1 gram of water 1 degree
  C at 1 atmosphere pressure

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1st Law of Thermodynamics

• Law of conservation of energy
• Amount of energy is constant in the universe
  although the form of the energy may change
• Never created or destroyed

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Internal Energy (E)

• Energy stored in a system
• ?E E2 E1 where 2 is after process or products
  and 1 is before process or reactants
• Change in heat content or enethalpy (H)
• ?H estimated to be ?E
• ?H Hproducts Hreactants
• -?H is exothermic, reactants release heat
• ?H is endothermic, heat taken up by reactants

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Exothermic and Endothermic
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2nd Law of Themodynamics

• Thermodynamic spontaneity whether a reaction or
  process can go but says nothing about whether it
  will go
• In every physical or chemical change, the
  universe always tends to greater disorder or
  randomness or entropy or free energy (S)
• ?S change in randomness

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Free Energy (G)

• Measure of spontaneity for a system
• ?G is related to changes in enthalpy and entropy
• ?H ?G T ?S where T is temperature in K
• Exothermic - ?H is negative and increase in
  entropy (?S) - ?G is negative
• Endothermic - ?H is and increase in entropy
  (?S) - ?G can be negative or positive

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?G
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Spontaneous Reactions

• Decrease in ?G, ?G is lt 0 and is negative
• Exergonic energy yielding in terms of ?G
• Endogonic energy requiring, increase in ?G
• Tells only that a reaction can go, potential to go

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Understanding ?G

• Equilibrium constant (Keq) is the ration of
  products to reactants at equilibrium
• A ? B Keq Beq/Aeq with B being product
  and A being reactants
• If concentration ratio is lt Keq then not enough
  of B and reaction will tend to go to the right to
  generate more B
• If concentration ratio is gt Keq then B is too
  high and the reaction will move to the left to
  make more A

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Free Energy vs Equilibrium

• Free energy is lowest at equilibrium
• The tendency for equilibrium is the driving force
  for every chemical reaction

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Standard Free Energy

• Standard state - 25C temperature, 1 atmosphere
  pressure, reactants and products at mol/L and at
  standard H
• ?G - standard free energy
• standard conditions
• pH 7
• ?G (?G at pH 7) is more useful
• If negative thermodynamically spontaneous
• If positive cannot occur in the direction
  written