Biology 107 Introduction to Metabolism I

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Biology 107Introduction to Metabolism I

• September 13, 2002

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Introduction to Metabolism I

• Student Objectives As a result of this lecture
  and the assigned reading, you should understand
  the following
• 1. Despite the organized structure of cells, all
  living things tend toward disorder. To maintain
  order, living things and the cells they are made
  up of depend on a continual flow of energy from
  the environment.
• 2. Metabolism is the sum total of an organism's
  chemical processing some chemical processes
  degrade complex molecules into simpler molecules
  (catabolic pathways), and some chemical processes
  synthesize complex molecules from simpler
  molecules (anabolic pathways).

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Introduction to Metabolism I

• 3. Energy can only be described and measured by
  how it affects matter. Energy is the capacity to
  perform work - all organisms require energy to
  stay alive, and all organisms transform energy.
• 4. There are two (2) forms of energy potential
  energy and kinetic energy.
• 5. The first law of thermodynamics (law of energy
  conservation) the total amount of energy in the
  universe is constant and energy can be
  transferred and transformed, but it cannot be
  created or destroyed.

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Introduction to Metabolism I

• The second law of thermodynamics energy
  conversions reduce the order of the universe.
  Heat, which is due to random molecular motion, is
  one form of disorder. The second law has direct
  applications to cellular activities - as
  explained in this law, energy cannot be
  transferred or transformed by the cell with 100
  efficiency.
• 7. Chemical reactions in living organisms - the
  starting substances of chemical reactions are
  called reactants reactants interact with one
  another to form new substances called products.
• 8. Chemical reactions, including those in cells,
  are of two types endergonic (energy-requiring)
  and exergonic (energy-releasing).

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Introduction to Metabolism I

• In an endergonic biosynthetic reaction, the
  electrons forming the chemical bonds of the
  product are at a higher energy level than the
  electrons of the reactants (i.e., the reaction
  requires input of energy).
• Cells supply the energy for endergonic reactions
  through coupled reactions in which endergonic
  reactions are linked to exergonic reactions.
• ATP is the cell's main energy carrier. Most
  frequently, coupled reactions use ATP as the
  energy source, and ATP is renewable energy that
  cells regenerate from exergonic reactions.

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Metabolic Pathways
Reactions occur in a stepwise fashion Pathways
are interconnected Chemical reactions are
catalyzed by enzymes
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Free Energy And Capacity To Do Work
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Need For Continual Flow Of Energy Into Systems
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Energy Profile For a Chemical Reaction
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Energy Profiles For Energy-requiring and
Energy-releasing Reactions
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Enzymes Lower Activation Energy But They Do Not
Change the Overall Energy Profile
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Coupling Of Energy-releasing Reactions With
Energy-requiring Reactions