Fig. 8-UN1

1
Fig. 8-UN1
Enzyme 1
Enzyme 2
Enzyme 3
D
C
B
A
Reaction 1
Reaction 3
Reaction 2
Product
Starting molecule
2
Fig. 8-2
Diving converts potential energy to kinetic
energy.
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.
A diver has less potential energy in the
water than on the platform.
3
Fig. 8-3
Heat
CO2

Chemical energy
H2O
(a) First law of thermodynamics
(b) Second law of thermodynamics
4
Fig. 8-6a
Reactants
Amount of energy released (?G lt 0)
Energy
Free energy
Products
Progress of the reaction
(a) Exergonic reaction energy released
5
Fig. 8-6b
Products
Amount of energy required (?G gt 0)
Energy
Free energy
Reactants
Progress of the reaction
(b) Endergonic reaction energy required
6
Fig. 8-8
Adenine
Phosphate groups
Ribose
7
Fig. 8-9
P
P
P
Adenosine triphosphate (ATP)
H2O
P

P
P
Energy

i
Inorganic phosphate
Adenosine diphosphate (ADP)
8
Fig. 8-UN1
Enzyme 1
Enzyme 2
Enzyme 3
D
C
B
A
Reaction 1
Reaction 3
Reaction 2
Product
Starting molecule
9
Fig. 8-15
Course of reaction without enzyme
EA without enzyme
EA with enzyme is lower
Reactants
Free energy
Course of reaction with enzyme
?G is unaffected by enzyme
Products
Progress of the reaction
10
Fig. 8-16
Substrate
Active site
Enzyme
Enzyme-substrate complex
(b)
(a)
11
Fig. 8-17
Substrates enter active site enzyme
changes shape such that its active site enfolds
the substrates (induced fit).
1
Substrates held in active site by
weak interactions, such as hydrogen bonds
and ionic bonds.
2
Substrates
Enzyme-substrate complex
Active site can lower EA and speed up a
reaction.
3
6
Active site is available for two
new substrate molecules.
Enzyme
Products are released.
5
4
Substrates are converted to products.
Products
12
Fig. 8-18
Optimal temperature for enzyme of thermophilic
(heat-tolerant) bacteria
Optimal temperature for typical human enzyme
Rate of reaction
0
20
40
80
60
100
Temperature (ºC)
(a) Optimal temperature for two enzymes
Optimal pH for pepsin (stomach enzyme)
Optimal pH for trypsin (intestinal enzyme)
Rate of reaction
5
4
3
2
1
0
6
7
8
9
10
pH
(b) Optimal pH for two enzymes
13
Fig. 8-19
Substrate
Active site
Competitive inhibitor
Enzyme
Noncompetitive inhibitor
(a) Normal binding
(c) Noncompetitive inhibition
(b) Competitive inhibition
14
Fig. 8-20a
Active site (one of four)
Allosteric enzyme with four subunits
Regulatory site (one of four)
Activator
Active form
Stabilized active form
Oscillation
Non- functional active site
Inhibitor
Stabilized inactive form
Inactive form
(a) Allosteric activators and inhibitors

15
Fig. 8-22
Initial substrate (threonine)
Active site available
Threonine in active site
Enzyme 1 (threonine deaminase)
Isoleucine used up by cell
Intermediate A
Feedback inhibition
Enzyme 2
Active site of enzyme 1 no longer
binds threonine pathway is switched off.
Intermediate B
Enzyme 3
Intermediate C
Isoleucine binds to allosteric site
Enzyme 4
Intermediate D
Enzyme 5
End product (isoleucine)
16
Fig. 8-20b
Substrate
Stabilized active form
Inactive form
(b) Cooperativity another type of allosteric
activation
17
Fig. 8-23
Mitochondria
1 µm