Climbing up converts the kinetic energy of muscle movement to ...

Fig. 8-2
A diver has more potential
energy on the platform
than in the water.
Climbing up converts the kinetic
energy of muscle movement
to potential energy.
Diving converts
potential energy to
kinetic energy.
A diver has less potential
energy in the water
than on the platform.

Fig. 8-5a
• More free energy (higher G)
• Less stable
• Greater work capacity
In a spontaneous change
• The free energy of the system
decreases (∆G < 0)
• The system becomes more
stable
• The released free energy can
be harnessed to do work
• Less free energy (lower G)
• More stable
• Less work capacity

Fig. 8-5b
Spontaneous
change
(a) Gravitational motion
Spontaneous
change
Spontaneous
change
(b) Diffusion (c) Chemical reaction

Free energy
Fig. 8-6a
Reactants
Energy
Progress of the reaction
(a) Exergonic reaction: energy released
Products
Amount of
energy
released
(∆G < 0)

Free energy
Fig. 8-6b
Reactants
Energy
Progress of the reaction
Products
(b) Endergonic reaction: energy required
Amount of
energy
required
(∆G > 0)

Fig. 8-7a
∆G < 0 ∆G = 0
(a) An isolated hydroelectric system

Fig. 8-7b
∆G < 0
(b) An open hydroelectric system

Fig. 8-7c
∆G < 0
∆G < 0
(c) A multistep open hydroelectric system
∆G < 0

Fig. 8-8
Phosphate groups
Adenine
Ribose

Fig. 8-9
Inorganic phosphate
P P P
Adenosine triphosphate (ATP)
P + P P
+
i
H 2 O
Adenosine diphosphate (ADP)
Energy

Fig. 8-10
1
2
Glu
Glutamic
acid
ATP phosphorylates
glutamic acid,
making the amino
acid less stable.
Ammonia displaces
the phosphate group,
forming glutamine.
+
(a) Endergonic reaction
Glu
Glu
NH 3
Ammonia
P
ATP
NH 3
(b) Coupled with ATP hydrolysis, an exergonic reaction
(c) Overall free-energy change
+
+
NH 2
Glu
Glutamine
∆G = +3.4 kcal/mol
Glu
NH 2
Glu
P
+
P
+ ADP
i

Fig. 8-11
ATP
Membrane protein
P
Solute Solute transported
(a) Transport work: ATP phosphorylates
transport proteins
Vesicle Cytoskeletal track
ATP
Motor protein Protein moved
(b) Mechanical work: ATP binds noncovalently
to motor proteins, then is hydrolyzed
P i
ADP
+
P i

Fig. 8-12
Energy from
catabolism (exergonic,
energy-releasing
processes)
ATP + H 2 O
ADP +
P i
Energy for cellular
work (endergonic,
energy-consuming
processes)

Fig. 8-13
Sucrose (C 12H 22O 11)
Sucrase
Glucose (C 6H 12O 6) Fructose (C 6H 12O 6)

Fig. 8-14
Free energy
A
C
B
D
Reactants
A
C
B
Transition state
E A
D
Progress of the reaction
A
C
B
D
Products
∆G < O

Free energy
Fig. 8-15
Course of
reaction
without
enzyme
Reactants
Course of
reaction
with enzyme
E A
without
enzyme
Progress of the reaction
Products
E A with
enzyme
is lower
∆G is unaffected
by enzyme

Fig. 8-16
Substrate
Active site
(a)
Enzyme Enzyme-substrate
complex
(b)

Fig. 8-17
1 Substrates enter active site; enzyme
changes shape such that its active site
enfolds the substrates (induced fit).
Substrates
6 Active
site is
available
for two new
substrate
molecules.
Enzyme
5
Products are
released.
Products
Enzyme-substrate
complex
2 Substrates held in
active site by weak
interactions, such as
hydrogen bonds and
ionic bonds.
4
Substrates are
converted to
products.
3 Active site can lower EA and speed up a reaction.

Fig. 8-18
Rate of reaction
Rate of reaction
Optimal temperature for
typical human enzyme
Optimal temperature for
enzyme of thermophilic
(heat-tolerant)
bacteria
0 20 40 60 80 100
Temperature (ºC)
(a) Optimal temperature for two enzymes
Optimal pH for pepsin
(stomach enzyme)
Optimal pH
for trypsin
(intestinal
enzyme)
0 1 2 3 4
pH
5 6 7 8 9 10
(b) Optimal pH for two enzymes

Fig. 8-19
Substrate
Active site
Enzyme
Competitive
inhibitor
Noncompetitive inhibitor
(a) Normal binding (b) Competitive inhibition (c) Noncompetitive inhibition

Fig. 8-20a
Allosteric enzyme
with four subunits
Regulatory
site (one
of four)
Nonfunctional
active
site
Oscillation
Inactive form
Active site
(one of four)
Activator
Active form Stabilized active form
Inhibitor
(a) Allosteric activators and inhibitors
Stabilized inactive
form

Fig. 8-20b
Inactive form
Substrate
Stabilized active
form
(b) Cooperativity: another type of allosteric activation

Fig. 8-22
Isoleucine
used up by
cell
Isoleucine
binds to
allosteric
site
Feedback
inhibition
Active site
available
Active site of
enzyme 1 no
longer binds
threonine;
pathway is
switched off.
Intermediate A
Enzyme 2
Intermediate B
Enzyme 3
Intermediate C
Enzyme 4
Intermediate D
Enzyme 5
Initial substrate
(threonine)
Threonine
in active site
Enzyme 1
(threonine
deaminase)
End product
(isoleucine)

Fig. 8-23
Mitochondria
1 µm