Biology in Focus - Chapter 7

Biology in Focus - Chapter 7 - Cellular Respiration and Fermentaion

1. CAMPBELL BIOLOGY IN FOCUS
© 2014 Pearson Education, Inc.
Urry • Cain • Wasserman • Minorsky • Jackson • Reece
Lecture Presentations by
Kathleen Fitzpatrick and Nicole Tunbridge
7
Cellular
Respiration
and Fermentation

2. Overview: Life Is Work
Living cells require energy from outside sources
Some animals, such as the giraffe, obtain energy by
eating plants, and some animals feed on other
organisms that eat plants
© 2014 Pearson Education, Inc.

3. © 2014 Pearson Education, Inc.
Figure 7.1

4. Energy flows into an ecosystem as sunlight and
leaves as heat
Photosynthesis generates O
2
and organic molecules,
which are used as fuel for cellular respiration
Cells use chemical energy stored in organic
molecules to regenerate ATP, which powers work
© 2014 Pearson Education, Inc.
Animation: Carbon Cycle

5. © 2014 Pearson Education, Inc.
Figure 7.2
Light
energy
ECOSYSTEM
Photosynthesis
in chloroplasts
CO
2
+ H
2
O
Cellular respiration
in mitochondria
Organic
molecules
+ O
2
ATP
ATP powers
most cellular work
Heat
energy

6. Concept 7.1: Catabolic pathways yield energy by
oxidizing organic fuels
Several processes are central to cellular respiration
and related pathways
© 2014 Pearson Education, Inc.

7. Catabolic Pathways and Production of ATP
The breakdown of organic molecules is exergonic
Fermentation is a partial degradation of sugars that
occurs without O
2
Aerobic respiration consumes organic molecules
and O
2
and yields ATP
Anaerobic respiration is similar to aerobic respiration
but consumes compounds other than O
2
© 2014 Pearson Education, Inc.

8. Cellular respiration includes both aerobic and
anaerobic respiration but is often used to refer to
aerobic respiration
Although carbohydrates, fats, and proteins are all
consumed as fuel, it is helpful to trace cellular
respiration with the sugar glucose
C
6
H
12
O
6
+ 6 O
2
® 6 CO
2
+ 6 H
2
O + Energy (ATP + heat)
© 2014 Pearson Education, Inc.

9. Redox Reactions: Oxidation and Reduction
The transfer of electrons during chemical reactions
releases energy stored in organic molecules
This released energy is ultimately used to synthesize
ATP
© 2014 Pearson Education, Inc.

10. The Principle of Redox
Chemical reactions that transfer electrons between
reactants are called oxidation-reduction reactions, or
redox reactions
In oxidation, a substance loses electrons, or is
oxidized
In reduction, a substance gains electrons, or is
reduced (the amount of positive charge is reduced)
© 2014 Pearson Education, Inc.

11. © 2014 Pearson Education, Inc.
Figure 7.UN01
becomes oxidized
(loses electron)
becomes reduced
(gains electron)

12. © 2014 Pearson Education, Inc.
Figure 7.UN02
becomes oxidized
becomes reduced

13. The electron donor is called the reducing agent
The electron acceptor is called the oxidizing agent
Some redox reactions do not transfer electrons but
change the electron sharing in covalent bonds
An example is the reaction between methane
and O
2
© 2014 Pearson Education, Inc.

14. © 2014 Pearson Education, Inc.
Figure 7.3
Reactants Products
Methane
(reducing
agent)
Oxygen
(oxidizing
agent)
Carbon dioxide Water
becomes reduced
becomes oxidized

15. Redox reactions that move electrons closer to
electronegative atoms, like oxygen, release chemical
energy that can be put to work
© 2014 Pearson Education, Inc.

16. Oxidation of Organic Fuel Molecules During
Cellular Respiration
During cellular respiration, the fuel (such as glucose)
is oxidized, and O
2
is reduced
Organic molecules with an abundance of hydrogen,
like carbohydrates and fats, are excellent fuels
As hydrogen (with its electron) is transferred to
oxygen, energy is released that can be used in ATP
sythesis
© 2014 Pearson Education, Inc.

17. © 2014 Pearson Education, Inc.
Figure 7.UN03
becomes oxidized
becomes reduced

18. Stepwise Energy Harvest via NAD
+
and the
Electron Transport Chain
In cellular respiration, glucose and other organic
molecules are broken down in a series of steps
Electrons from organic compounds are usually first
transferred to NAD
+
, a coenzyme
As an electron acceptor, NAD
+
functions as an
oxidizing agent during cellular respiration
Each NADH (the reduced form of NAD
+
) represents
stored energy that is tapped to synthesize ATP
© 2014 Pearson Education, Inc.

19. © 2014 Pearson Education, Inc.
Figure 7.4
NAD
+
Nicotinamide
(oxidized form)
Nicotinamide
(reduced form)
Oxidation of NADH
Reduction of NAD
+
Dehydrogenase
NADH
+ 2[H]
(from food)
2 e
−
+ 2 H
+
2 e
−
+ H
+
H
+
H
+
+

20. © 2014 Pearson Education, Inc.
Figure 7.4a
NAD
+
Nicotinamide
(oxidized form)

21. © 2014 Pearson Education, Inc.
Figure 7.4b
Nicotinamide
(reduced form)
Oxidation of NADH
Reduction of NAD
+
Dehydrogenase
NADH
2 e
−
+ 2 H
+
2 e
−
+ H
+
H
+
H
+
+ 2[H]
(from food)
+

22. © 2014 Pearson Education, Inc.
Figure 7.UN04

23. NADH passes the electrons to the electron
transport chain
Unlike an uncontrolled reaction, the electron
transport chain passes electrons in a series of steps
instead of one explosive reaction
O
2
pulls electrons down the chain in an energy-
yielding tumble
The energy yielded is used to regenerate ATP
© 2014 Pearson Education, Inc.

24. © 2014 Pearson Education, Inc.
Figure 7.5
Explosive
release
(a) Uncontrolled reaction (b) Cellular respiration
H
2
O
F
r
e
e

e
n
e
r
g
y
,

G
F
r
e
e

e
n
e
r
g
y
,

G
E
l
e
c
t
r
o
n

t
r
a
n
s
p
o
r
t
c
h
a
i
n
Controlled
release of
energy
H
2
O
2 H
+
2 e
−
2 H
+
+ 2 e
−
ATP
ATP
ATP
½
½
½H
2
+O
2 O
2
O
2
2 H +

25. The Stages of Cellular Respiration: A Preview
Harvesting of energy from glucose has three stages
Glycolysis (breaks down glucose into two molecules
of pyruvate)
Pyruvate oxidation and the citric acid cycle
(completes the breakdown of glucose)
Oxidative phosphorylation (accounts for most of
the ATP synthesis)
© 2014 Pearson Education, Inc.
Animation: Cellular Respiration

26. © 2014 Pearson Education, Inc.
Figure 7.UN05
Glycolysis (color-coded teal throughout the chapter)
Pyruvate oxidation and the citric acid cycle
(color-coded salmon)
1.
Oxidative phosphorylation: electron transport and
chemiosmosis (color-coded violet)
2.
3.

27. © 2014 Pearson Education, Inc.
Figure 7.6-1
Electrons
via NADH
Glycolysis
Glucose Pyruvate
CYTOSOL
ATP
Substrate-level
MITOCHONDRION

28. © 2014 Pearson Education, Inc.
Figure 7.6-2
Electrons
via NADH
Glycolysis
Glucose Pyruvate
Pyruvate
oxidation
Acetyl CoA
Citric
acid
cycle
Electrons
via NADH and
FADH
2
CYTOSOL
ATP
Substrate-level
ATP
Substrate-level
MITOCHONDRION

29. © 2014 Pearson Education, Inc.
Figure 7.6-3
Electrons
via NADH
Glycolysis
Glucose Pyruvate
Pyruvate
oxidation
Acetyl CoA
Citric
acid
cycle
Electrons
via NADH and
FADH
2
Oxidative
phosphorylation:
electron transport
and
chemiosmosis
CYTOSOL
ATP
Substrate-level
ATP
Substrate-level
MITOCHONDRION
ATP
Oxidative

30. The process that generates most of the ATP is
called oxidative phosphorylation because it is
powered by redox reactions
© 2014 Pearson Education, Inc.

31. Oxidative phosphorylation accounts for almost 90%
of the ATP generated by cellular respiration
A smaller amount of ATP is formed in glycolysis and
the citric acid cycle by substrate-level
phosphorylation
For each molecule of glucose degraded to CO
2
and
water by respiration, the cell makes up to 32
molecules of ATP
© 2014 Pearson Education, Inc.

32. © 2014 Pearson Education, Inc.
Figure 7.7
Substrate
P
ADP
Product
ATP+
Enzyme
Enzyme

33. Concept 7.2: Glycolysis harvests chemical energy
by oxidizing glucose to pyruvate
Glycolysis (“sugar splitting”) breaks down glucose
into two molecules of pyruvate
Glycolysis occurs in the cytoplasm and has two
major phases
Energy investment phase
Energy payoff phase
Glycolysis occurs whether or not O
2
is present
© 2014 Pearson Education, Inc.

34. © 2014 Pearson Education, Inc.
Figure 7.UN06
Glycolysis
Pyruvate
oxidation
Citric
acid
cycle
Oxidative
phosphorylation
ATP ATP ATP

35. © 2014 Pearson Education, Inc.
Figure 7.8
Energy Investment Phase
Energy Payoff Phase
Net
Glucose
Glucose
2 ADP + 2P
4 ADP + 4P
2 NAD
+
+ 4 e
−
+ 4 H
+
2 NAD
+
+ 4 e
−
+ 4 H
+
4 ATP formed − 2 ATP used
2 ATP
4 ATP
used
formed
2 NADH+ 2 H
+
2 Pyruvate + 2 H
2
O
2 Pyruvate + 2 H
2
O
2 NADH + 2 H
+
2 ATP

36. © 2014 Pearson Education, Inc.
Figure 7.9a
Glycolysis: Energy Investment Phase
Glucose
ATP
ADP
Glucose
6-phosphate
Phosphogluco-
isomerase
Hexokinase
1
2 3
4
ATP
ADP
Fructose
6-phosphate
Phospho-
fructokinase
Fructose
1,6-bisphosphate
Aldolase
Isomerase
5
Glyceraldehyde
3-phosphate (G3P)
Dihydroxyacetone
phosphate (DHAP)

37. © 2014 Pearson Education, Inc.
Figure 7.9aa-1
Glycolysis: Energy Investment Phase
Glucose

38. © 2014 Pearson Education, Inc.
Figure 7.9aa-2
Glycolysis: Energy Investment Phase
Glucose
Glucose
6-phosphate
ADP
ATP
Hexokinase
1

39. © 2014 Pearson Education, Inc.
Figure 7.9aa-3
Glycolysis: Energy Investment Phase
Glucose
Glucose
6-phosphate
ADP
ATP
Hexokinase
1
Fructose
6-phosphate
Phosphogluco-
isomerase
2

40. © 2014 Pearson Education, Inc.
Figure 7.9ab-1
Glycolysis: Energy Investment Phase
Fructose
6-phosphate

41. © 2014 Pearson Education, Inc.
Figure 7.9ab-2
Glycolysis: Energy Investment Phase
Fructose
6-phosphate
Phospho-
fructokinase
3
Fructose
1,6-bisphosphate
ATP
ADP

42. © 2014 Pearson Education, Inc.
Figure 7.9ab-3
Glycolysis: Energy Investment Phase
Fructose
6-phosphate
Phospho-
fructokinase
3
Aldolase
Isomerase
4
5
Fructose
1,6-bisphosphate
Glyceraldehyde
3-phosphate (G3P)
ATP
ADP
Dihydroxyacetone
phosphate (DHAP)

43. © 2014 Pearson Education, Inc.
Figure 7.9b
Glycolysis: Energy Payoff Phase
2 NAD
+
Glyceraldehyde
3-phosphate (G3P)
Triose
phosphate
dehydrogenase
6
+ 2 H
+
2 NADH
2
2P
i
1,3-Bisphospho-
glycerate
3-Phospho-
glycerate
2-Phospho-
glycerate
Phosphoenol-
pyruvate (PEP)
Pyruvate
Phospho-
glycerokinase
Phospho-
glyceromutase
Enolase Pyruvate
kinase
2 ADP
2 2 2 2
2 ADP
2 ATP
2 H
2O
2 ATP
9
1087

44. © 2014 Pearson Education, Inc.
Figure 7.9ba-1
Isomerase
4
Glyceraldehyde
3-phosphate (G3P)
Dihydroxyacetone
phosphate (DHAP)
Glycolysis: Energy Payoff Phase
Aldolase
5

45. © 2014 Pearson Education, Inc.
Figure 7.9ba-2
Isomerase
Glyceraldehyde
3-phosphate (G3P)
Dihydroxyacetone
phosphate (DHAP)
Glycolysis: Energy Payoff Phase
2 NAD
+
Triose
phosphate
dehydrogenase
+ 2 H
+
2 NADH
2
1,3-Bisphospho-
glycerate
2
Aldolase
P
i
5
6
4

46. © 2014 Pearson Education, Inc.
Figure 7.9ba-3
Isomerase
Glyceraldehyde
3-phosphate (G3P)
Dihydroxyacetone
phosphate (DHAP)
Glycolysis: Energy Payoff Phase
2 NAD
+
Triose
phosphate
dehydrogenase
+ 2 H
+
2 NADH
2
1,3-Bisphospho-
glycerate
3-Phospho-
glycerate
Phospho-
glycerokinase
2 ADP
2 ATP
2
Aldolase
P
i
2
5
7
6
4

47. © 2014 Pearson Education, Inc.
Figure 7.9bb-1
3-Phospho-
glycerate
Glycolysis: Energy Payoff Phase
2

48. © 2014 Pearson Education, Inc.
Figure 7.9bb-2
83-Phospho-
glycerate
Glycolysis: Energy Payoff Phase
Phospho-
glyceromutase
222
2 H
2
O
2-Phospho-
glycerate
Phosphoenol-
pyruvate (PEP)
Enolase
9

49. © 2014 Pearson Education, Inc.
Figure 7.9bb-3
3-Phospho-
glycerate
Glycolysis: Energy Payoff Phase
2 ATP
Phospho-
glyceromutase
2222
2 ADP
2 H
2
O
2-Phospho-
glycerate
Phosphoenol-
pyruvate (PEP)
Pyruvate
Enolase Pyruvate
kinase
9
108

50. Concept 7.3: After pyruvate is oxidized, the citric
acid cycle completes the energy-yielding oxidation
of organic molecules
In the presence of O
2
, pyruvate enters the
mitochondrion (in eukaryotic cells), where the
oxidation of glucose is completed
Before the citric acid cycle can begin, pyruvate must
be converted to acetyl coenzyme A (acetyl CoA),
which links glycolysis to the citric acid cycle
© 2014 Pearson Education, Inc.

51. © 2014 Pearson Education, Inc.
Figure 7.UN07
Glycolysis
Pyruvate
oxidation
Citric
acid
cycle
Oxidative
phosphorylation
ATP ATP ATP

52. © 2014 Pearson Education, Inc.
Figure 7.10
CYTOSOL
Pyruvate
(from glycolysis,
2 molecules per glucose)
CO
2
CoA
NAD
+
NADH
MITOCHONDRION CoA
CoA
Acetyl CoA
+ H
+
Citric
acid
cycle
FADH
2
FAD
ADP +P
i
ATP
NADH
3 NAD
+
3
+ 3 H
+
2CO
2

53. © 2014 Pearson Education, Inc.
Figure 7.10a
CYTOSOL
Pyruvate
(from glycolysis,
2 molecules per glucose)
CO
2
CoA
NAD
+
NADH
MITOCHONDRION CoA
Acetyl CoA
+ H
+

54. © 2014 Pearson Education, Inc.
Figure 7.10b
CoA
Citric
acid
cycle
FADH
2
FAD
ADP +P
i
ATP
NADH
3 NAD
+
3
+ 3 H
+
2CO
2
CoA
Acetyl CoA

55. The citric acid cycle, also called the Krebs cycle,
completes the breakdown of pyruvate to CO
2
The cycle oxidizes organic fuel derived from
pyruvate, generating 1 ATP, 3 NADH, and 1 FADH
2

per turn
© 2014 Pearson Education, Inc.

56. © 2014 Pearson Education, Inc.
Figure 7.UN08
Glycolysis
Pyruvate
oxidation
Oxidative
phosphorylation
ATP ATP ATP
Citric
acid
cycle

57. © 2014 Pearson Education, Inc.
Figure 7.11-1
Acetyl CoA
Oxaloacetate
CoA-SH
Citrate
H
2
O
Isocitrate
Citric
acid
cycle
2
1

58. © 2014 Pearson Education, Inc.
Figure 7.11-2
Acetyl CoA
Oxaloacetate
Citrate
H
2
O
Isocitrate
NADH
NAD
+
+ H
+
CO
2
a-Ketoglutarate
Citric
acid
cycle
3
1
CoA-SH
2

59. © 2014 Pearson Education, Inc.
Figure 7.11-3
Acetyl CoA
Oxaloacetate
Citrate
H
2
O
Isocitrate
NADH
NAD
+
+ H
+
CO
2
a-Ketoglutarate
Citric
acid
cycle
CoA-SH
CO
2
NAD
+
NADH
+ H
+
Succinyl
CoA
4
1
3
CoA-SH
2

60. © 2014 Pearson Education, Inc.
Figure 7.11-4
Acetyl CoA
Oxaloacetate
Citrate
H
2
O
Isocitrate
NADH
NAD
+
+ H
+
CO
2
a-Ketoglutarate
Citric
acid
cycle
CoA-SH
CO
2
NAD
+
NADH
+ H
+
ATP formation
Succinyl
CoA
ADP
GDPGTP
P
i
ATP
Succinate
5
4
1
CoA-SH
3
CoA-SH
2

61. © 2014 Pearson Education, Inc.
Figure 7.11-5
Malate
Succinate
FAD
FADH
2
Fumarate
H
2
O
7
6
Acetyl CoA
Oxaloacetate
Citrate
H
2
O
Isocitrate
NADH
NAD
+
+ H
+
CO
2
a-Ketoglutarate
Citric
acid
cycle
CoA-SH
CO
2
NAD
+
NADH
+ H
+
ATP formation
Succinyl
CoA
ADP
GDPGTP
P
i
ATP
5
4
1
CoA-SH
3
CoA-SH
2

62. © 2014 Pearson Education, Inc.
Figure 7.11-6
NADH
NAD
+
+ H
+
8
Malate
Succinate
FAD
FADH
2
Fumarate
H
2
O
7
6
Acetyl CoA
Oxaloacetate
Citrate
H
2
O
Isocitrate
NADH
NAD
+
+ H
+
CO
2
a-Ketoglutarate
Citric
acid
cycle
CoA-SH
CO
2
NAD
+
NADH
+ H
+
ATP formation
Succinyl
CoA
ADP
GDPGTP
P
i
ATP
5
4
1
CoA-SH
3
CoA-SH
2

63. © 2014 Pearson Education, Inc.
Figure 7.11a
CoA-SH
Acetyl CoA
Start: Acetyl CoA adds its
two-carbon group to
oxaloacetate, producing
citrate; this is a highly
exergonic reaction.
Oxaloacetate
Citrate
Isocitrate
H
2
O1
2

64. © 2014 Pearson Education, Inc.
Figure 7.11b
Isocitrate
Redox reaction:
Isocitrate is oxidized;
NAD
+
is reduced.
Redox reaction:
After CO
2
release, the resulting
four-carbon molecule is oxidized
(reducing NAD
+
), then made
reactive by addition of CoA.
CO
2
release
CO
2
release
a-Ketoglutarate
Succinyl
CoA
NAD
+
NADH
+ H
+
CO
2
CO
2
CoA-SH
NAD
+
NADH
+ H
+
3
4

65. © 2014 Pearson Education, Inc.
Figure 7.11c
CoA-SH
Redox reaction:
Succinate is oxidized;
FAD is reduced.
Fumarate
Succinate
Succinyl
CoA
ATP formation
ATP
ADP
GDPGTP
FAD
FADH
2
P
i
5
6

66. © 2014 Pearson Education, Inc.
Figure 7.11d
Redox reaction:
Malate is oxidized;
NAD
+
is reduced.
Fumarate
Malate
Oxaloacetate
H
2
O
NAD
+
+ H
+
NADH
7
8

67. The citric acid cycle has eight steps, each catalyzed
by a specific enzyme
The acetyl group of acetyl CoA joins the cycle by
combining with oxaloacetate, forming citrate
The next seven steps decompose the citrate back to
oxaloacetate, making the process a cycle
The NADH and FADH
2
produced by the cycle relay
electrons extracted from food to the electron
transport chain
© 2014 Pearson Education, Inc.

68. Concept 7.4: During oxidative phosphorylation,
chemiosmosis couples electron transport to ATP
synthesis
Following glycolysis and the citric acid cycle, NADH
and FADH
2
account for most of the energy extracted
from food
These two electron carriers donate electrons to the
electron transport chain, which powers ATP synthesis
via oxidative phosphorylation
© 2014 Pearson Education, Inc.

69. The Pathway of Electron Transport
The electron transport chain is in the inner
membrane (cristae) of the mitochondrion
Most of the chain’s components are proteins, which
exist in multiprotein complexes
The carriers alternate reduced and oxidized states as
they accept and donate electrons
Electrons drop in free energy as they go down the
chain and are finally passed to O
2
, forming H
2
O
© 2014 Pearson Education, Inc.

70. © 2014 Pearson Education, Inc.
Figure 7.UN09
Glycolysis
Pyruvate
oxidation
Citric
acid
cycle
Oxidative
phosphorylation:
electron transport
and chemiosmosis
ATP ATP ATP

71. © 2014 Pearson Education, Inc.
Figure 7.12
Multiprotein
complexes
(originally from
NADH or FADH
2
)
F
r
e
e

e
n
e
r
g
y

(
G
)

r
e
l
a
t
i
v
e

t
o

O
2

(
k
c
a
l
/
m
o
l
)
50
40
30
20
10
0
NADH
NAD
+
FADH
2
FAD
2
2
e
−
e
−
FMN
Fe•S
Fe•S
Q
I
II
III
Cyt b
Cyt c
1
Fe•S
Cyt c
IV
Cyt a
Cyt a
3
2e
−
O
22 H
+
+ ½
H
2
O

72. © 2014 Pearson Education, Inc.
Figure 7.12a
Multiprotein
complexes
F
r
e
e

e
n
e
r
g
y

(
G
)

r
e
l
a
t
i
v
e

t
o

O
2

(
k
c
a
l
/
m
o
l
)
50
40
30
20
10
NADH
NAD
+
FADH
2
FAD
2
2
e
−
e
−
FMN
Fe•S
Fe•S
Q
I
II
III
Cyt b
Cyt c
1
Fe•S
Cyt c
IV
Cyt a
Cyt a
3
2e
−

73. © 2014 Pearson Education, Inc.
Figure 7.12b
30
20
10
0
Cyt c
1
Cyt c
IV
Cyt a
Cyt a
3
2e
−
F
r
e
e

e
n
e
r
g
y

(
G
)

r
e
l
a
t
i
v
e

t
o

O
2

(
k
c
a
l
/
m
o
l
)
(originally from
NADH or FADH
2
)
2 H
+
+ ½O
2
H
2O

74. Electrons are transferred from NADH or FADH
2
to the
electron transport chain
Electrons are passed through a number of proteins
including cytochromes (each with an iron atom)
to O
2
The electron transport chain generates no ATP
directly
It breaks the large free-energy drop from food to O
2

into smaller steps that release energy in manageable
amounts
© 2014 Pearson Education, Inc.

75. Chemiosmosis: The Energy-Coupling Mechanism
Electron transfer in the electron transport chain
causes proteins to pump H
+
from the mitochondrial
matrix to the intermembrane space
H
+
then moves back across the membrane, passing
through the protein complex, ATP synthase
ATP synthase uses the exergonic flow of H
+
to drive
phosphorylation of ATP
This is an example of chemiosmosis, the use of
energy in a H
+
gradient to drive cellular work
© 2014 Pearson Education, Inc.

76. © 2014 Pearson Education, Inc.
Video: ATP Synthase 3-D Side View
Video: ATP Synthase 3-D Top View

77. © 2014 Pearson Education, Inc.
Figure 7.13
INTERMEMBRANE SPACE
MITOCHONDRIAL MATRIX
Rotor
Internal rod
Catalytic knob
Stator
H
+
ATP
ADP
P
i
+

78. The energy stored in a H
+
gradient across a
membrane couples the redox reactions of the electron
transport chain to ATP synthesis
The H
+
gradient is referred to as a proton-motive
force, emphasizing its capacity to do work
© 2014 Pearson Education, Inc.

79. © 2014 Pearson Education, Inc.
Figure 7.UN09
Glycolysis
Pyruvate
oxidation
Citric
acid
cycle
Oxidative
phosphorylation:
electron transport
and chemiosmosis
ATP ATP ATP

80. © 2014 Pearson Education, Inc.
Figure 7.14
Protein
complex
of electron
carriers
H
+
H
+
H
+
H
+
Q
I
II
III
FADH
2
FAD
NAD
+
NADH
(carrying electrons
from food)
Electron transport chain
Oxidative phosphorylation
Chemiosmosis
ATP
synthase
H
+
ADP + ATPP
i
H
2
O2 H
+
+ ½ O
2
IV
Cyt c
1 2

81. © 2014 Pearson Education, Inc.
Figure 7.14a
Protein
complex
of electron
carriers
H
+
Q
I
II
III
FADH
2
FAD
NAD
+
NADH
(carrying electrons
from food)
Electron transport chain
H
2
O2 H
+
+ ½ O
2
Cyt c
1
IV
H
+
H
+

82. © 2014 Pearson Education, Inc.
Figure 7.14b
ATP
synthase
Chemiosmosis2
H
+
H
+
ADP +P
i
ATP

83. An Accounting of ATP Production by Cellular
Respiration
During cellular respiration, most energy flows in the
following sequence:
glucose ® NADH ® electron transport chain ®
proton-motive force ® ATP
About 34% of the energy in a glucose molecule is
transferred to ATP during cellular respiration,
making about 32 ATP
There are several reasons why the number of ATP
molecules is not known exactly
© 2014 Pearson Education, Inc.

84. © 2014 Pearson Education, Inc.
Figure 7.15
Electron shuttles
span membrane
CYTOSOL
2 NADH
2 NADH
2 FADH
2
or
2 NADH
Glycolysis
Glucose
2
Pyruvate
Pyruvate
oxidation
2 Acetyl CoA
Citric
acid
cycle
6 NADH2 FADH
2
Oxidative
phosphorylation:
electron transport
and
chemiosmosis
+ about 26 or 28 ATP+ 2 ATP + 2 ATP
About
30 or 32 ATP
Maximum per glucose:
MITOCHONDRION

85. © 2014 Pearson Education, Inc.
Figure 7.15a
Electron shuttles
span membrane
2 NADH
2 FADH
2
or
2 NADH
Glycolysis
Glucose
2
Pyruvate
+ 2 ATP

86. © 2014 Pearson Education, Inc.
Figure 7.15b
2 NADH 6 NADH2 FADH
2
Citric
acid
cycle
Pyruvate
oxidation
2 Acetyl CoA
+ 2 ATP

87. © 2014 Pearson Education, Inc.
Figure 7.15c
2 NADH
2 NADH 6 NADH2 FADH
2
2 FADH
2
or
Oxidative
phosphorylation:
electron transport
and
chemiosmosis
+ about 26 or 28 ATP

88. © 2014 Pearson Education, Inc.
Figure 7.15d
Maximum per glucose:
About
30 or 32 ATP

89. Concept 7.5: Fermentation and anaerobic
respiration enable cells to produce ATP without
the use of oxygen
Most cellular respiration requires O
2
to produce ATP
Without O
2
, the electron transport chain will cease to
operate
In that case, glycolysis couples with fermentation or
anaerobic respiration to produce ATP
© 2014 Pearson Education, Inc.

90. Anaerobic respiration uses an electron transport
chain with a final electron acceptor other than O
2
, for
example, sulfate
Fermentation uses substrate-level phosphorylation
instead of an electron transport chain to generate
ATP
© 2014 Pearson Education, Inc.

91. Types of Fermentation
Fermentation consists of glycolysis plus reactions
that regenerate NAD
+
, which can be reused by
glycolysis
Two common types are alcohol fermentation and
lactic acid fermentation
© 2014 Pearson Education, Inc.

92. In alcohol fermentation, pyruvate is converted to
ethanol in two steps
The first step releases CO
2
from pyruvate, and the
second step reduces acetaldehyde to ethanol
Alcohol fermentation by yeast is used in brewing,
winemaking, and baking
© 2014 Pearson Education, Inc.
Animation: Fermentation Overview

93. © 2014 Pearson Education, Inc.
Figure 7.16
2 ADP + 2 2 ATPP
i
Glucose Glycolysis
2 Pyruvate
2CO
2
2 NADH
+ 2 H
+
2 NAD
+
2 Ethanol
(a) Alcohol fermentation
2 Acetaldehyde
(b) Lactic acid fermentation
2 Lactate
2 NADH
+ 2 H
+
2 NAD
+
2 Pyruvate
Glycolysis
2 ATP2 ADP + 2P
i
Glucose

94. © 2014 Pearson Education, Inc.
Figure 7.16a
2 ADP + 2 2 ATPP
i
Glucose Glycolysis
2 Pyruvate
2CO
2
2 NADH
+ 2 H
+
2 NAD
+
2 Ethanol
(a) Alcohol fermentation
2 Acetaldehyde

95. © 2014 Pearson Education, Inc.
Figure 7.16b
2 ADP + 2 2 ATPP
i
Glucose Glycolysis
2 Pyruvate
2 NADH
+ 2 H
+
2 NAD
+
(b) Lactic acid fermentation
2 Lactate

96. In lactic acid fermentation, pyruvate is reduced by
NADH, forming lactate as an end product, with no
release of CO
2
Lactic acid fermentation by some fungi and bacteria
is used to make cheese and yogurt
Human muscle cells use lactic acid fermentation to
generate ATP when O
2
is scarce
© 2014 Pearson Education, Inc.

97. Comparing Fermentation with Anaerobic and
Aerobic Respiration
All use glycolysis (net ATP = 2) to oxidize glucose
and harvest chemical energy of food
In all three, NAD
+
is the oxidizing agent that accepts
electrons during glycolysis
The processes have different final electron acceptors:
an organic molecule (such as pyruvate or
acetaldehyde) in fermentation and O
2
in cellular
respiration
Cellular respiration produces 32 ATP per glucose
molecule; fermentation produces 2 ATP per glucose
molecule
© 2014 Pearson Education, Inc.

98. Obligate anaerobes carry out only fermentation or
anaerobic respiration and cannot survive in the
presence of O
2
Yeast and many bacteria are facultative anaerobes,
meaning that they can survive using either
fermentation or cellular respiration
In a facultative anaerobe, pyruvate is a fork in the
metabolic road that leads to two alternative catabolic
routes
© 2014 Pearson Education, Inc.

99. © 2014 Pearson Education, Inc.
Figure 7.17
Glucose
CYTOSOL
Glycolysis
Pyruvate
O
2
present:
Aerobic cellular
respiration
No O
2
present:
Fermentation
Ethanol,
lactate, or
other products
Acetyl CoA
Citric
acid
cycle
MITOCHONDRION

100. The Evolutionary Significance of Glycolysis
Ancient prokaryotes are thought to have used
glycolysis long before there was oxygen in the
atmosphere
Very little O
2
was available in the atmosphere until
about 2.7 billion years ago, so early prokaryotes
likely used only glycolysis to generate ATP
Glycolysis is a very ancient process
© 2014 Pearson Education, Inc.

101. Concept 7.6: Glycolysis and the citric acid cycle
connect to many other metabolic pathways
Gycolysis and the citric acid cycle are major
intersections to various catabolic and anabolic
pathways
© 2014 Pearson Education, Inc.

102. The Versatility of Catabolism
Catabolic pathways funnel electrons from many kinds
of organic molecules into cellular respiration
Glycolysis accepts a wide range of carbohydrates
Proteins must be digested to amino acids and amino
groups must be removed before amino acids can
feed glycolysis or the citric acid cycle
© 2014 Pearson Education, Inc.

103. Fats are digested to glycerol (used in glycolysis) and
fatty acids
Fatty acids are broken down by beta oxidation and
yield acetyl CoA
An oxidized gram of fat produces more than twice as
much ATP as an oxidized gram of carbohydrate
© 2014 Pearson Education, Inc.

104. © 2014 Pearson Education, Inc.
Figure 7.18-1
Proteins
Amino
acids
Carbohydrates
Sugars
Fats
GlycerolFatty
acids

105. © 2014 Pearson Education, Inc.
Figure 7.18-2
Proteins
Amino
acids
Carbohydrates
Sugars
Glucose
Glycolysis
Glyceraldehyde 3-
Pyruvate
P
NH
3
Fats
GlycerolFatty
acids

106. © 2014 Pearson Education, Inc.
Figure 7.18-3
Proteins
Amino
acids
Carbohydrates
Sugars
Glucose
Glycolysis
Glyceraldehyde 3-
Pyruvate
P
Acetyl CoA
NH
3
Fats
GlycerolFatty
acids

107. © 2014 Pearson Education, Inc.
Figure 7.18-4
Proteins
Amino
acids
Carbohydrates
Sugars
Glucose
Glycolysis
Glyceraldehyde 3-
Pyruvate
P
Acetyl CoA
Citric
acid
cycle
NH
3
Fats
GlycerolFatty
acids

108. © 2014 Pearson Education, Inc.
Figure 7.18-5
Proteins
Amino
acids
Carbohydrates
Sugars
Glucose
Glycolysis
Glyceraldehyde 3-
Pyruvate
P
Acetyl CoA
Citric
acid
cycle
NH
3
Fats
GlycerolFatty
acids
Oxidative
phosphorylation

109. Biosynthesis (Anabolic Pathways)
The body uses small molecules to build other
substances
Some of these small molecules come directly from
food; others can be produced during glycolysis or
the citric acid cycle
© 2014 Pearson Education, Inc.

110. © 2014 Pearson Education, Inc.
Figure 7.UN10a

111. © 2014 Pearson Education, Inc.
Figure 7.UN10b

112. © 2014 Pearson Education, Inc.
Figure 7.UN11
Inputs
Glucose
Glycolysis
2 Pyruvate + 2
Outputs
ATP NADH+ 2

113. © 2014 Pearson Education, Inc.
Figure 7.UN12
Inputs
2 Pyruvate 2 Acetyl CoA
2 Oxaloacetate
Citric
acid
cycle
Outputs
ATP
CO
2
2
6 2
8NADH
FADH
2

114. © 2014 Pearson Education, Inc.
Figure 7.UN13a
Protein
complex
of electron
carriers
INTERMEMBRANE
SPACE
MITOCHONDRIAL MATRIX
(carrying electrons from food)
NADH NAD
+
FADH
2
FAD
Cyt c
Q
I
II
III
IV
2 H
+
+
½O
2
H
2
O
H
+
H
+
H
+

115. © 2014 Pearson Education, Inc.
Figure 7.UN13b
INTER-
MEMBRANE
SPACE
MITO-
CHONDRIAL
MATRIX
ATP
synthase
ATPADP + H
+
H
+
P
i

116. © 2014 Pearson Education, Inc.
Figure 7.UN14
Time
p
H

d
i
f
f
e
r
e
n
c
e
a
c
r
o
s
s

m
e
m
b
r
a
n
e