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					        Biology 107

Introduction to Metabolism I


     September 9, 2005
     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).
     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.
     Introduction to Metabolism I
6.   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).
      Introduction to Metabolism I
9.    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).

10.   Cells supply the energy for endergonic reactions through coupled
      reactions in which endergonic reactions are linked to exergonic
      reactions.

11.   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.
  Metabolic
  Pathways
Reactions occur in a
stepwise fashion
Pathways are
interconnected
Chemical reactions
are catalyzed by
enzymes
Free Energy And Capacity To Do Work
Need For Continual Flow Of Energy Into Systems
A Cell Does Three Main Kinds of
             Work
Mechanical work, such as the beating of cilia (Chapter 6),
the contraction of muscle cells, and the movement of
chromosomes during cellular reproduction

Transport work, the pumping of substances across
membranes against the direction of spontaneous
movement (Chapter 7)

Chemical work, the pushing of endergonic reactions,
which would not occur spontaneously, such as the
synthesis of polymers from monomers (the focus of this
chapter, and Chapters 9 and 10)
Energy Profile For a Chemical Reaction
Energy Profiles For Energy-requiring and Energy-
               releasing Reactions
Enzymes Lower Activation Energy But They
 Do Not Change the Overall Energy Profile
Coupling Of Energy-releasing Reactions With
        Energy-requiring Reactions
     ATP, GTP, UTP, CTP
All nucleotide triphosphates contain high energy
bonds. Although ATP is the primary cellular energy
carrier, other nucleotide triphosphates may provide
energy to specific chemical reactions.

				
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