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Biology
Sylvia S. Mader
Michael Windelspecht
Chapter 6
Metabolism:
Energy and
Enzymes
Lecture Outline
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6.1 Cells and the Flow of
Energy
• Energy – The ability to do work or bring
about a change
 Kinetic energy
• Energy of motion
• Mechanical
 Potential energy
• Stored energy
• Chemical energy
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Flow of Energy
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solar
energy
heat
heat
heat
Chemical
energy
Mechanical energy
3
Two Laws of
Thermodynamics
• First law:
 Law of conservation of energy
 Energy cannot be created or destroyed, but can be
changed from one form to another
• Second law:
 Law of entropy
 When energy is changed from one form to another,
there is a loss of usable energy
 Waste energy goes to increase disorder
4
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heat
CO2
sun
H 2O
carbohydrate
solar energy
producer
Carbohydrate Metabolism
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
heat
carbohydrate
uncontracted muscle
contracted muscle
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Cells and Entropy
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H2O
C6H12O6
CO2
Glucose
Carbon dioxide
and water
• more organized
• more potential energy
• less stable (entropy)
a.
kinetic
energy
• less organized
• less potential energy
• more stable (entropy)
H+
H+
channel protein
H+
H+
H+
H+
H+
H+
H+
Unequal distribution
of hydrogen ions
• more organized
• more potential energy
• less stable (entropy)
b.
H+
H+
H+
H+
H+
H+
H+
H+
H+
Equal distribution
of hydrogen ions
• less organized
• less potential energy
• more stable (entropy)
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6.2 Metabolic Reactions and Energy
Transformations
• Metabolism
 Sum of cellular chemical reactions in cell
 Reactants participate in a reaction
 Products form as result of a reaction
• Free energy is the amount of energy available
to perform work
 Exergonic Reactions - Products have less free
energy than reactants (release energy)
 Endergonic Reactions - Products have more free
energy than reactants (require energy input)
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ATP: Energy for Cells
• Adenosine triphosphate (ATP)
 High energy compound used to drive metabolic
reactions
 Constantly being generated from adenosine
diphosphate (ADP)
• Composed of:
 Adenine, ribose (together = adenosine), and three
phosphate groups
• Coupled reactions
 Energy released by an exergonic reaction
captured in ATP
 ATP is used to drive an endergonic reaction
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The ATP Cycle
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adenosine triphosphate
ATP is unstable and has
a high potential energy.
P
P
P
ATP
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The ATP Cycle
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
adenosine triphosphate
ATP is unstable and has
a high potential energy.
P
P
P
ATP
ATP +
P
Endergonic Reaction:
• The hydrolysis of ATP releases
previously stored energy, allowing
the change in free energy to do
work and drive other processes.
• Has negative delta G.
• Examples: protein synthesis, nerve
conduction, muscle contraction
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The ATP Cycle
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
adenosine triphosphate
ATP is unstable and has
a high potential energy.
P
P
P
ATP
ADP
+
P
Endergonic Reaction:
• The hydrolysis of ATP releases
Previously stored energy, allowing
the change in free energy to do
work and drive other processes.
• Has negative delta G.
• Examples: protein synthesis, nerve
conduction, muscle contraction
P
P
+
P
+
adenosine diphosphate
phosphate
ADP is more stable and has lower potential energy than ATP.
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The ATP Cycle
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
adenosine triphosphate
ATP is unstable and has
a high potential energy.
P
P
P
Exergonic Reaction:
• Creation of ATP from
ADP and Prequires
input of energy from
Other sources.
ATP
• Has positive delta G.
• Example: cellular
respiration
ADP
+
P
Endergonic Reaction:
• The hydrolysis of ATP releases
Previously stored energy, allowing
the change in free energy to do
work and drive other processes.
• Has negative delta G.
• Examples: protein synthesis, nerve
conduction, muscle contraction
P
P
+
P
+
adenosine diphosphate
phosphate
ADP is more stable and has lower potential energy than ATP.
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