Transcript Free Energy

Free Energy
Ch. 6
Overview of Free Energy
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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
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
Definitions
• Free energy –
–The amount of energy left to do
work after a chemical reaction has
occurred
• Entropy –
–The relative amount of disorder
• Disorder happens spontaneously
• Organization requires energy
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More Organized
Disorder happens
spontaneously
Less Organized
Lower Entropy
Increased Entropy
More Potential
Energy
Less Potential
Energy
Less Stable
More Stable
Organization
requires energy
© Jill Braaten
Cells and Entropy
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H2O
More
Organized
Less
Organized
C6H12O6
CO2
Lower
Entropy
Glucose
• more organized
• more potential energy
• less stable (entropy)
a.
More
Potential
Energy
kinetic
energy
• less organized
• less potential energy
• more stable (entropy)
H+
H+
channel protein
H+
H+
H+
Less
Stable
H+
H+
H+
H+
H+
H+
H+
H+
H+
Unequal distribution
of hydrogen ions
• more organized
• more potential energy
• less stable (entropy)
b.
Increased
Entropy
Carbon dioxide
and water
H+
H+
H+
H+
Equal distribution
of hydrogen ions
• less organized
• less potential energy
• more stable (entropy)
Less
Potential
Energy
More
Stable
7
Entropy and Free Energy
• Reactions that increase entropy have a
negative change in free energy (-ΔG)
– The products have less free energy than the
reactants
– Energy is released (Exergonic Reaction)
– The reaction occurs spontaneously
Entropy and Free Energy
• Reactions that decrease entropy have a
positive change in free energy (+ΔG)
– The products have more energy than the
reactants
– Requires energy input (Endergonic Reaction)
Living Things Require Free Energy
• Life requires a highly ordered system
– Order is maintained by a constant input of free
energy into the system
– Loss of order or free energy results in death.
Flow of Energy
solar
energy
heat
heat
Chemical
energy
heat
Mechanical energy
12
Living Systems and the 2nd Law of
Thermodynamics
• Increased disorder and entropy are offset by
biological processes that maintain or increase
order.
– Reactions that increase entropy (negative change
in free energy) are coupled with reactions that
decrease entropy (positive change in free energy).
ATP
• Fee energy becomes available for metabolism
and other processes by the conversion of ATP
to ADP, which is coupled to many energy
requiring reactions.
Coupled Reactions
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1
2
Myosin assumes its
resting shape when
It combines with ATP.
ATP splits into ADP
and p , causing
myosin to change its
shape and allowing it
to attach to actin.
3
Release of ADP and
p cause myosin to
again change shape
and pull against actin,
generating force and
motion.
actin
myosin
ATP
P
ADP
15
The ATP Cycle
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adenosine triphosphate
ATP is unstable and has
a high potential energy.
P
P
P
ATP
16
The ATP Cycle
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adenosine triphosphate
ATP is unstable and has
a high potential energy.
P
• Creation of ATP from
ADP and requires
input of energy from
Other sources.
P
P
ATP
• Has positive delta G.
• Example: cellular
respiration
ADP
+
P
• 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.
17
• Organisms use fee energy to maintain
organization, grow and reproduce.
– Organisms use various strategies to regulate body
temperature and metabolism:
• Endothermy – the use of thermal energy generated by
metabolism to maintain homeostatic body temperature
• Ectothermy – the use of external thermal energy to
help regulate and maintain body temperature
Animation
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