Metabolism: Energy and Enzymes

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Chapter 6

• Metabolism Energy and Enzymes

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6.1 Cells and the flow of energy

• Energy the ability to do work or bring about
  change
• Organisms need a constant supply of energy to
  maintain organization and carry out metabolic
  activities
• Flow of energy fig. 6.1

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Forms of Energy

• Kinetic energy of motion (a ball rolling down a
  hill)
• Potential stored energy (the food we eat has
  potential energy)
• Chemical chemical composition of substances
  makes them possess energy, such as lipids, carbs,
  etc.
• Mechanical a type of kinetic in which an
  organism is using its chemical energy and
  converting it (ie. An organism walking)

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Laws of Thermodynamics

• These two laws explain why energy flows in
  ecosystems and cells
• Energy starts from the sun, and flows, it does
  not cycle. Some of the suns energy is
  dissipated as heat but most of it is used by
  plants for photosynthesis and animals when they
  eat. Eventually all solar energy is dissipated
  as heat.

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First Law of Thermodynamics

• Law of conservation of energy energy cannot be
  created or destroyed, only changed from one form
  or another
• See picture on p. 102, solar energy being used by
  a plant to convert carbon dioxide and water into
  carbohydrates, and energy being lost as heat

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Second Law of Thermodynamics

• Energy cannot be changed from one form to another
  without a loss of usable energy
• See picture on p. 103, carbohydrates being used
  for muscle contraction and some of the energy
  being lost as heat

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Cells and entropy

• Entropy a relative amount of disorganization
• Processes that occur in cells naturally tend to
  move toward entropy.
• See fig. 6.2 and consider the messy room
  analogy a neat room is more organized but less
  stable than a messy room (its easier to mess
  up), while a messy room is more stable but less
  organized (harder to clean up)

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ENTROPY
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6.2 Metabolic Reactions and Energy Transformations

• Metabolism the sum of all chemical reactions
  that occur in the body
• Reactants substances in a chemical reaction that
  begin the reaction
• Products the result of the reaction
• In the reaction on the right, circle the
  reactants and draw a square around the products

• Direct combination or synthesis, in which 2 or
  more chemical elements or compounds unite to form
  a more complex product
• N2 3 H2 ? 2 NH

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Free energy

• The amount of energy available, still free to
  do work, after a chemical reaction has occurred
• From Wikipedia, the Gibbs free energy ?G equals
  the work exchanged by the system with its
  surroundings, less the work of the pressure
  forces, during a reversible transformation of the
  system from the same initial state to the same
  final state.

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Exergonic Reactions

• When there is a negative ?G, therefore energy is
  released.
• Cellular respiration is an exergonic reaction

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Endergonic reaction

• The ones in which ?G is positive and energy is
  absorbed
• Examples protein synthesis, nerve conduction,
  muscle contraction

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Adenosine Triphosphate (ATP)

• The common energy currency of cells, when cells
  require energy, they spend ATP
• The more active an organism, the greater its
  demand for ATP
• It is constantly being generated from ADP
  (adenosine diphosphate) and a molecule of
  inorganic phosphate
• Glucose breakdown during cellular respiration
  provides the energy for the buildup of ATP in
  mitochondria

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Structure of ATP
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Coupled Reactions

• When reactions are both exergonic and endergonic
  energy is first released by an exergonic reaction
  and in turn used to drive an endergonic reaction
• See fig. 6.4 first ATP is broken down to get
  energy and then that energy is used in muscle
  contraction

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Functions of ATP

• Uses of ATP in living systems
• Chemical ATP provides the cell energy to
  synthesize macromolecules
• Transport ATP provides energy for cells to
  transport molecules across membranes
• Mechanical enables muscle contraction, cells to
  move, cell division, etc.

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For next time(MONDAY)

• We will finish ch. 6 notes
• READ chapter 6!!!
• On page 112 do reviewing ch. 1-7
• Study session MON after school for one hour!
• TEST (chapters 2-6) TUES
• Come tomorrow to randomly choose your take home
  essay, due TUES