Transcript Chapter 6.1-2 Notes

Chapter 6
Metabolism: Energy and Enzymes
6.1: Cells and the flow of
energy
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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
Forms of Energy
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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 it’s chemical energy and
converting it (ie. An organism walking)
Laws of Thermodynamics
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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 sun’s 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.
First Law of
Thermodynamics
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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
Second Law of
Thermodynamics
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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
Cells and entropy
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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 (it’s easier to
mess up), while a messy room is more
stable but less organized (harder to clean
up)
ENTROPY
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
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Direct combination or
synthesis, in which 2 or
more chemical elements or
compounds unite to form a
more complex product:
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N2 + 3 H2 → 2 NH
Free energy
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The amount of energy available, still ‘free’ to
do work, after a chemical reaction has
occurred
From Wikipedia, “the Gibbs free energy ΔG
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.“
Exergonic Reactions
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When there is a
negative ΔG,
therefore energy is
released.
Cellular respiration
is an exergonic
reaction
Endergonic reaction
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The ones in which ΔG is positive and
energy is absorbed
Examples: protein synthesis, nerve
conduction, muscle contraction
Adenosine Triphosphate
(ATP)
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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
Structure of ATP
Coupled Reactions
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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
Functions of ATP
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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….
For next time(MONDAY)
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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