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CAMPBELL
BIOLOGY Reece • Urry • Cain • Wasserman • Minorsky • Jackson
© 2014 Pearson Education, Inc.
TENTH
EDITION
CAMPBELL
BIOLOGY Reece • Urry • Cain • Wasserman • Minorsky • Jackson
TENTH
EDITION
Cellular
Respiration and
Fermentation
Lecture Presentation by
Nicole Tunbridge and
Kathleen Fitzpatrick
9
© 2014 Pearson Education, Inc.
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.
Figure 9.1
© 2014 Pearson Education, Inc.
Energy flows into an ecosystem as sunlight and
leaves as heat
Photosynthesis generates O2 and organic
molecules, which are used in cellular respiration
Cells use chemical energy stored in organic
molecules to generate ATP, which powers work
© 2014 Pearson Education, Inc.
Figure 9.2
Light energy
Organic molecules
O2 CO2 H2O +
Photosynthesis in chloroplasts
Cellular respiration in mitochondria
ECOSYSTEM
ATP powers most cellular work ATP
Heat energy
+
© 2014 Pearson Education, Inc.
BioFlix: The Carbon Cycle
© 2014 Pearson Education, Inc.
Concept 9.1: Catabolic pathways yield energy by oxidizing organic fuels
Catabolic pathways release stored energy by
breaking down complex molecules
Electron transfer plays a major role in these
pathways
These processes are central to cellular respiration
© 2014 Pearson Education, Inc.
Catabolic Pathways and Production of ATP
The breakdown of organic molecules is exergonic
Fermentation is a partial degradation of sugars
that occurs without O2
Aerobic respiration consumes organic molecules
and O2 and yields ATP
Anaerobic respiration is similar to aerobic
respiration but consumes compounds other
than O2
© 2014 Pearson Education, Inc.
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
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy (ATP + heat)
© 2014 Pearson Education, Inc.
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
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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.
Figure 9.UN01
becomes oxidized
(loses electron)
becomes reduced
(gains electron)
© 2014 Pearson Education, Inc.
Figure 9.UN02
becomes oxidized
becomes reduced
© 2014 Pearson Education, Inc.
The electron donor is called the reducing agent
The electron receptor 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 O2
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Figure 9.3
Reactants Products
Methane (reducing
agent)
Oxygen (oxidizing
agent)
Carbon dioxide Water
becomes oxidized
becomes reduced
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Oxidation of Organic Fuel Molecules During Cellular Respiration
During cellular respiration, the fuel (such as
glucose) is oxidized, and O2 is reduced
© 2014 Pearson Education, Inc.
Figure 9.UN03
becomes oxidized
becomes reduced
© 2014 Pearson Education, Inc.
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.
Figure 9.4
NAD+
2 e− + 2 H+
2[H] (from food)
Nicotinamide (oxidized form)
Reduction of NAD+
2 e− + H+
NADH
Nicotinamide (reduced form)
Oxidation of NADH H+
H+
Dehydrogenase
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Figure 9.4a
NAD+
Nicotinamide (oxidized form)
© 2014 Pearson Education, Inc.
Figure 9.4b
2 e− + 2 H+
Reduction of NAD+
2 e− + H+
NADH
Nicotinamide (reduced form)
Oxidation of NADH H+
H+
Dehydrogenase
2[H] (from food)
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Figure 9.UN04
Dehydrogenase
© 2014 Pearson Education, Inc.
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
O2 pulls electrons down the chain in an energy-
yielding tumble
The energy yielded is used to regenerate ATP
© 2014 Pearson Education, Inc.
Figure 9.5
H2 + ½ O2
2 H + ½ O2
2 H+
2 e−
2 e− 2 H+ +
H2O
½ O2
Controlled release of
energy
ATP
ATP
ATP
Explosive release
Cellular respiration Uncontrolled reaction (a) (b)
Fre
e e
nerg
y,
G
Fre
e e
nerg
y,
G
H2O
© 2014 Pearson Education, Inc.
The Stages of Cellular Respiration: A Preview
Harvesting of energy from glucose has three
stages
Glycolysis (breaks down glucose into two
molecules of pyruvate)
The citric acid cycle (completes the breakdown of
glucose)
Oxidative phosphorylation (accounts for most of
the ATP synthesis)
© 2014 Pearson Education, Inc.
Figure 9.UN05
1.
2.
3.
GLYCOLYSIS (color-coded blue throughout the chapter)
PYRUVATE OXIDATION and the CITRIC ACID CYCLE
(color-coded orange)
OXIDATIVE PHOSPHORYLATION: Electron transport and
chemiosmosis (color-coded purple)
© 2014 Pearson Education, Inc.
Figure 9.6-1
Electrons via NADH
ATP
CYTOSOL MITOCHONDRION
Substrate-level
GLYCOLYSIS
Glucose Pyruvate
© 2014 Pearson Education, Inc.
Figure 9.6-2
Electrons via NADH
Electrons via NADH
and FADH2
ATP ATP
CYTOSOL MITOCHONDRION
Substrate-level Substrate-level
GLYCOLYSIS PYRUVATE OXIDATION CITRIC
ACID CYCLE Acetyl CoA Glucose Pyruvate
© 2014 Pearson Education, Inc.
Figure 9.6-3
Electrons via NADH
Electrons via NADH
and FADH2
ATP ATP ATP
CYTOSOL MITOCHONDRION
Substrate-level Substrate-level Oxidative
GLYCOLYSIS PYRUVATE OXIDATION CITRIC
ACID CYCLE
OXIDATIVE PHOSPHORYLATION
(Electron transport and chemiosmosis)
Acetyl CoA Glucose Pyruvate
© 2014 Pearson Education, Inc.
BioFlix: Cellular Respiration
© 2014 Pearson Education, Inc.
The process that generates most of the ATP is
called oxidative phosphorylation because it is
powered by redox reactions
© 2014 Pearson Education, Inc.
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 CO2
and water by respiration, the cell makes up to 32
molecules of ATP
© 2014 Pearson Education, Inc.
Figure 9.7
Enzyme Enzyme
Substrate
Product
ATP
ADP
P
© 2014 Pearson Education, Inc.
Concept 9.2: 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 O2 is present
© 2014 Pearson Education, Inc.
Figure 9.UN06
GLYCOLYSIS PYRUVATE
OXIDATION
CITRIC
ACID
CYCLE
OXIDATIVE
PHOSPHORYL-
ATION
ATP
© 2014 Pearson Education, Inc.
Figure 9.8
Energy Investment Phase
Glucose
Energy Payoff Phase
Net
2 ATP used 2 ADP + 2 P
4 ADP + 4 P 4 ATP formed
NAD+ 4 e− 2 + + 4 H+ 2 H+ 2 NADH
Pyruvate 2
2
2
2
2
2
2
2 H+ H+
4
4
Glucose Pyruvate
ATP ATP used ATP formed
H2O
NADH
−
2 NAD+
+
+
+
+ + +
2 H2O
4 e−
© 2014 Pearson Education, Inc.
Figure 9.9a
GLYCOLYSIS: Energy Investment Phase
ADP
Glucose 6-phosphate
Fructose 6-phosphate
ATP ATP
ADP
Glyceraldehyde 3-phosphate (G3P)
Fructose 1,6-bisphosphate
Dihydroxyacetone phosphate (DHAP)
Glucose
Hexokinase Phosphogluco- isomerase
Phospho- fructokinase
Aldolase
Isomerase
1 2
5
4 3
© 2014 Pearson Education, Inc.
Figure 9.9aa-1
GLYCOLYSIS: Energy Investment Phase
Glucose
© 2014 Pearson Education, Inc.
Figure 9.9aa-2
GLYCOLYSIS: Energy Investment Phase
Glucose 6-phosphate
ATP
ADP Glucose
Hexokinase
1
© 2014 Pearson Education, Inc.
Figure 9.9aa-3
GLYCOLYSIS: Energy Investment Phase
Glucose 6-phosphate
ATP
ADP Glucose
Hexokinase Phosphogluco- isomerase
Fructose 6-phosphate
1 2
© 2014 Pearson Education, Inc.
Figure 9.9ab-1
GLYCOLYSIS: Energy Investment Phase
Fructose 6-phosphate
© 2014 Pearson Education, Inc.
Figure 9.9ab-2
GLYCOLYSIS: Energy Investment Phase
3
Fructose 6-phosphate
ATP
ADP
Fructose 1,6-bisphosphate
Phospho- fructokinase
© 2014 Pearson Education, Inc.
Figure 9.9ab-3
GLYCOLYSIS: Energy Investment Phase
3 4
5
Fructose 6-phosphate
ATP
ADP
Glyceraldehyde 3-phosphate (G3P)
Fructose 1,6-bisphosphate
Dihydroxyacetone phosphate (DHAP)
Phospho- fructokinase
Aldolase
Isomerase
© 2014 Pearson Education, Inc.
Figure 9.9b
GLYCOLYSIS: Energy Payoff Phase
Glycer-
aldehyde
3-phosphate
(G3P)
Triose
phosphate
dehydrogenase
6 1,3-Bisphospho-
glycerate
3-Phospho-
glycerate
2-Phospho-
glycerate
Phosphoenol-
pyruvate (PEP)
Pyruvate
Phospho-
glycerokinase
Phospho-
glyceromutase
Enolase Pyruvate
kinase
2 NAD+
7 8 9
10
2 NADH
+ 2 H+
2
2
2
2
2 2 2 2
2
2 2 H2O
ATP ATP ADP
ADP
© 2014 Pearson Education, Inc.
Figure 9.9ba-1
GLYCOLYSIS: Energy Payoff Phase
4
Glyceraldehyde
3-phosphate (G3P)
Dihydroxyacetone
phosphate (DHAP)
Aldolase
Isomerase
5
© 2014 Pearson Education, Inc.
Figure 9.9ba-2
GLYCOLYSIS: Energy Payoff Phase
4
Glyceraldehyde
3-phosphate (G3P)
Dihydroxyacetone
phosphate (DHAP)
Aldolase
Isomerase
5 6
Triose
phosphate
dehydrogenase
2 NAD+ 2 H+
NADH
2
2
2
2
1,3-Bisphospho-
glycerate
© 2014 Pearson Education, Inc.
Figure 9.9ba-3
GLYCOLYSIS: Energy Payoff Phase
4
Glyceraldehyde
3-phosphate (G3P)
Dihydroxyacetone
phosphate (DHAP)
Aldolase
Isomerase
5 6 7
Triose
phosphate
dehydrogenase
2 NAD+ 2 H+
NADH
2
2
2
2
2 ADP
1,3-Bisphospho-
glycerate
3-Phospho-
glycerate
Phospho-
glycerokinase
2
2
ATP
© 2014 Pearson Education, Inc.
Figure 9.9bb-1
3-Phospho-
glycerate
2
GLYCOLYSIS: Energy Payoff Phase
© 2014 Pearson Education, Inc.
Figure 9.9bb-2
8 9
Phospho-
glyceromutase
3-Phospho-
glycerate
2-Phospho-
glycerate
2 2 2
Enolase
Phosphoenol-
pyruvate (PEP)
2 H2O
GLYCOLYSIS: Energy Payoff Phase
© 2014 Pearson Education, Inc.
Figure 9.9bb-3
8 9
10
Phospho-
glyceromutase
3-Phospho-
glycerate
2-Phospho-
glycerate
2 2 2
Enolase
Phosphoenol-
pyruvate (PEP)
Pyruvate
Pyruvate
kinase
2
2 ATP ADP
2 H2O 2
GLYCOLYSIS: Energy Payoff Phase
© 2014 Pearson Education, Inc.
Concept 9.3: After pyruvate is oxidized, the citric acid cycle completes the energy-yielding oxidation of organic molecules
In the presence of O2, pyruvate enters the
mitochondrion (in eukaryotic cells) where the
oxidation of glucose is completed
© 2014 Pearson Education, Inc.
Oxidation of Pyruvate to Acetyl CoA
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
This step is carried out by a multienzyme complex
that catalyses three reactions
© 2014 Pearson Education, Inc.
Figure 9.UN07
GLYCOLYSIS PYRUVATE
OXIDATION
CITRIC
ACID
CYCLE
OXIDATIVE
PHOSPHORYL-
ATION
© 2014 Pearson Education, Inc.
Figure 9.10
CYTOSOL
Pyruvate
Transport protein
MITOCHONDRION
Acetyl CoA NAD+ H+ NADH +
CO2
Coenzyme A
1
2
3
© 2014 Pearson Education, Inc.
The Citric Acid Cycle
The citric acid cycle, also called the Krebs cycle,
completes the break down of pyruvate to CO2
The cycle oxidizes organic fuel derived from
pyruvate, generating 1 ATP, 3 NADH, and 1
FADH2 per turn
© 2014 Pearson Education, Inc.
Figure 9.11
PYRUVATE OXIDATION
Pyruvate (from glycolysis,
2 molecules per glucose)
NADH
NAD+
CO2
CoA
CoA
+ H+
CoA
CoA
CO2
CITRIC
ACID
CYCLE
FADH2
FAD
ATP
ADP + P i
NAD+
+ 3 H+
NADH 3
3
2
Acetyl CoA
© 2014 Pearson Education, Inc.
Figure 9.11a
PYRUVATE OXIDATION
Pyruvate (from glycolysis,
2 molecules per glucose)
NADH
NAD+
CO2
CoA
CoA
+ H+ Acetyl CoA
© 2014 Pearson Education, Inc.
Figure 9.11b
CoA
CoA
CO2
CITRIC
ACID
CYCLE
FADH2
FAD
ATP
ADP + P i
NAD+
+ 3 H+
NADH 3
3
2
Acetyl CoA
© 2014 Pearson Education, Inc.
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 FADH2 produced by the cycle
relay electrons extracted from food to the electron
transport chain
© 2014 Pearson Education, Inc.
Figure 9.UN08
GLYCOLYSIS PYRUVATE
OXIDATION
CITRIC
ACID
CYCLE
OXIDATIVE
PHOSPHORYL-
ATION
ATP
© 2014 Pearson Education, Inc.
Figure 9.12-1
Acetyl CoA
Oxaloacetate
CoA-SH
Citrate
CITRIC
ACID
CYCLE
1
© 2014 Pearson Education, Inc.
Figure 9.12-2
Acetyl CoA
H2O
Oxaloacetate
CoA-SH
Citrate
CITRIC
ACID
CYCLE
Isocitrate
1
2
© 2014 Pearson Education, Inc.
Figure 9.12-3
Acetyl CoA
H2O
+ H+
Oxaloacetate
CoA-SH
Citrate
-Ketoglutarate
NAD+
CO2
NADH CITRIC
ACID
CYCLE
Isocitrate
1
2
3
© 2014 Pearson Education, Inc.
Figure 9.12-4
Acetyl CoA
H2O
+ H+
Oxaloacetate
CoA-SH
Citrate
-Ketoglutarate
CoA-SH
NAD+
CO2
NADH
CO2 NAD+
NADH
+ H+
Succinyl
CoA
CITRIC
ACID
CYCLE
Isocitrate
1
2
4
3
© 2014 Pearson Education, Inc.
Figure 9.12-5
Acetyl CoA
H2O
+ H+
Oxaloacetate
CoA-SH
Citrate
-Ketoglutarate
CoA-SH
NAD+
CO2
NADH
CO2 NAD+
NADH
+ H+
Succinyl
CoA
ATP
ADP
GTP GDP
Succinate
CITRIC
ACID
CYCLE
P i
Isocitrate
1
2
5
4
3
CoA-SH
© 2014 Pearson Education, Inc.
Figure 9.12-6
Acetyl CoA
H2O
+ H+
Oxaloacetate
CoA-SH
Citrate
-Ketoglutarate
CoA-SH
NAD+
CO2
NADH
CO2 NAD+
NADH
+ H+
Succinyl
CoA
ATP
ADP
GTP GDP
Succinate
FAD
FADH2
Fumarate
CITRIC
ACID
CYCLE
P i
Isocitrate
1
2
5
6 4
3
CoA-SH
© 2014 Pearson Education, Inc.
Figure 9.12-7
Acetyl CoA
H2O
+ H+
Oxaloacetate
CoA-SH
Citrate
-Ketoglutarate
CoA-SH
NAD+
CO2
NADH
CO2 NAD+
NADH
+ H+
Succinyl
CoA
ATP
ADP
GTP GDP
Succinate
FAD
FADH2
Fumarate
H2O
Malate
CITRIC
ACID
CYCLE
P i
Isocitrate
1
2
5
6 4
3 7
CoA-SH
© 2014 Pearson Education, Inc.
Figure 9.12-8
Acetyl CoA
H2O
+ H+
Oxaloacetate
CoA-SH
Citrate
-Ketoglutarate
CoA-SH
NAD+
CO2
NADH
CO2 NAD+
NADH
+ H+
Succinyl
CoA
ATP
ADP
GTP GDP
Succinate
FAD
FADH2
Fumarate
H2O
Malate
CITRIC
ACID
CYCLE
+ H+
NAD+
P i
NADH
Isocitrate
1
2
5
6 4
3 7
8
CoA-SH
© 2014 Pearson Education, Inc.
Figure 9.12a
Acetyl CoA
Oxaloacetate
Citrate Isocitrate
H2O
CoA-SH
1
2
© 2014 Pearson Education, Inc.
Figure 9.12b
3
4 -Ketoglutarate
CO2
NAD+
NADH
+ H+
CO2
NAD+
NADH
+ H+
CoA-SH
Isocitrate
Succinyl
CoA
© 2014 Pearson Education, Inc.
Figure 9.12c
Succinyl
CoA
6
5
Fumarate
FADH2
FAD
Succinate
GTP GDP
ADP
ATP
P i
CoA-SH
© 2014 Pearson Education, Inc.
Figure 9.12d
NADH
Oxaloacetate
Malate
Fumarate
H2O
7
8
NAD+
+ H+
© 2014 Pearson Education, Inc.
Concept 9.4: During oxidative phosphorylation, chemiosmosis couples electron transport to ATP synthesis
Following glycolysis and the citric acid cycle,
NADH and FADH2 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.
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 O2, forming H2O
© 2014 Pearson Education, Inc.
Figure 9.UN09
GLYCOLYSIS CITRIC
ACID
CYCLE
PYRUVATE
OXIDATION
ATP
OXIDATIVE
PHOSPHORYL-
ATION
© 2014 Pearson Education, Inc.
Figure 9.13
NADH
e− 2 NAD+
FADH2
FAD 2 e
−
FMN
Fe•S
Q
Fe•S
Cyt b
Fe•S
Cyt c1
Cyt c
Cyt a
Cyt a3
e− 2
(originally from
NADH or FADH2)
2 H+ + ½ O2
H2O
Multiprotein
complexes I
II
III
IV
50
40
30
20
10
0
Fre
e e
nerg
y (
G)
rela
tive
to
O2 (
kc
al/
mo
l)
© 2014 Pearson Education, Inc.
Figure 9.13a
50
40
30
20
10
Fre
e e
ne
rgy (
G)
rela
tiv
e t
o O
2 (
kc
al/m
ol)
NADH
e− 2
NAD+
FADH2
Fe•S
e−
FMN
Fe•S
Q
Cyt b
FAD I
II
FAD
Multiprotein
complexes
III
Fe•S
Cyt c1
Cyt c
Cyt a
Cyt a3
IV
2
e− 2
© 2014 Pearson Education, Inc.
Figure 9.13b
30
20
10
Fre
e e
ne
rgy (
G)
rela
tiv
e t
o O
2 (
kc
al/m
ol)
0
Cyt c1
Cyt c
Cyt a
Cyt a3
IV
e− 2
2 H+ + ½ O2
H2O
(originally from
NADH or FADH2)
© 2014 Pearson Education, Inc.
Electrons are transferred from NADH or FADH2 to
the electron transport chain
Electrons are passed through a number of
proteins including cytochromes (each with an iron
atom) to O2
The electron transport chain generates no ATP
directly
It breaks the large free-energy drop from food to
O2 into smaller steps that release energy in
manageable amounts
© 2014 Pearson Education, Inc.
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.
Figure 9.14
INTERMEMBRANE
SPACE Rotor
H+ Stator
Internal rod
Catalytic
knob
ADP + P i
MITOCHONDRIAL
MATRIX
ATP
© 2014 Pearson Education, Inc.
Video: ATP Synthase 3-D Structure, Top View
© 2014 Pearson Education, Inc.
Video: ATP Synthase 3-D Structure, Side View
© 2014 Pearson Education, Inc.
Figure 9.15
Protein
complex
of electron
carriers
(carrying
electrons
from
food)
ATP
synthase
Electron transport chain Chemiosmosis
Oxidative phosphorylation
2 H+ + ½ O2 H2O
ADP + P i
H+
ATP
H+
H+
H+
H+
Cyt c
Q
I
II
III
IV
FAD FADH2
NADH NAD+
1 2
© 2014 Pearson Education, Inc.
Figure 9.15a
Protein complex of electron carriers
2 H+ + ½ O2 H2O
H+
NAD+
1
H+
H+
NADH
FADH2
Cyt c Cyt c
IV
III
II
I
FAD
(carrying electrons from food) Electron transport chain
Q
© 2014 Pearson Education, Inc.
Figure 9.15b
H+
2
H+
ADP + P i ATP
Chemiosmosis
ATP
synthase
© 2014 Pearson Education, Inc.
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.
An Accounting of ATP Production by Cellular Respiration
During cellular respiration, most energy flows in
this 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
is not known exactly
© 2014 Pearson Education, Inc.
Figure 9.16
Electron shuttles
span membrane
CYTOSOL 2 NADH
or
2 FADH2
2 NADH 2 FADH2 6 NADH
MITOCHONDRION
OXIDATIVE
PHOSPHORYLATION
(Electron transport
and chemiosmosis)
CITRIC
ACID
CYCLE
PYRUVATE
OXIDATION
2 Acetyl CoA
GLYCOLYSIS
Glucose 2 Pyruvate
+ 2 ATP + 2 ATP
Maximum per glucose: About
30 or 32 ATP
+ about 26 or 28 ATP
2 NADH
© 2014 Pearson Education, Inc.
Figure 9.16a
Electron shuttles
span membrane
+ 2 ATP
2 NADH or
2 FADH2
GLYCOLYSIS
Glucose 2 Pyruvate
2 NADH
© 2014 Pearson Education, Inc.
Figure 9.16b
2 FADH2 6 NADH
CITRIC
ACID
CYCLE
PYRUVATE
OXIDATION
2 Acetyl CoA
+ 2 ATP
2 NADH
© 2014 Pearson Education, Inc.
Figure 9.16c
2 NADH or
2 FADH2
2 NADH 2 FADH2 6 NADH
OXIDATIVE
PHOSPHORYLATION
(Electron transport
and chemiosmosis)
+ about 26 or 28 ATP
© 2014 Pearson Education, Inc.
Figure 9.16d
Maximum per glucose: About
30 or 32 ATP
© 2014 Pearson Education, Inc.
Concept 9.5: Fermentation and anaerobic respiration enable cells to produce ATP without the use of oxygen
Most cellular respiration requires O2 to produce
ATP
Without O2, the electron transport chain will cease
to operate
In that case, glycolysis couples with anaerobic
respiration or fermentation to produce ATP
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Anaerobic respiration uses an electron transport
chain with a final electron acceptor other than O2,
for example sulfate
Fermentation uses substrate-level phosphorylation
instead of an electron transport chain to generate
ATP
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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
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In alcohol fermentation, pyruvate is converted to
ethanol in two steps
The first step releases CO2
The second step produces ethanol
Alcohol fermentation by yeast is used in brewing,
winemaking, and baking
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Figure 9.17
2 ADP + 2 P i 2 ATP
Glucose
2 NAD+ NADH 2
+ 2 H+
2 Pyruvate
CO2 2
2 Ethanol
(a) Alcohol fermentation
2 Acetaldehyde 2 Lactate
Lactic acid fermentation
2 ADP + 2 P i 2 ATP
GLYCOLYSIS
NAD+
+ 2 H+
NADH 2 2
2 Pyruvate
(b)
GLYCOLYSIS Glucose
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Figure 9.17a
2 ADP + 2 P i
NAD+
+ 2 H+
GLYCOLYSIS Glucose
2 ATP
2 2
2 Ethanol 2 Acetaldehyde
2 Pyruvate
(a) Alcohol fermentation
2 CO2 NADH
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Figure 9.17b
2 ADP + 2 P i
NAD+
+ 2 H+
GLYCOLYSIS Glucose
2 ATP
2 2
Lactate
(b) Lactic acid fermentation
NADH
2 Pyruvate
2
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Animation: Fermentation Overview
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In lactic acid fermentation, pyruvate is reduced
by NADH, forming lactate as an end product, with
no release of CO2
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 O2 is scarce
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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
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The processes have different mechanisms for
oxidizing NADH:
In fermentation, an organic molecule (such as
pyruvate or acetaldehyde) acts as a final electron
acceptor
In cellular respiration electrons are transferred to
the electron transport chain
Cellular respiration produces 32 ATP per glucose
molecule; fermentation produces 2 ATP per
glucose molecule
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Obligate anaerobes carry out fermentation or
anaerobic respiration and cannot survive in the
presence of O2
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
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Figure 9.18
Glucose
Glycolysis CYTOSOL
Pyruvate
No O2 present:
Fermentation
O2 present:
Aerobic cellular
respiration
Ethanol,
lactate, or
other products
MITOCHONDRION
Acetyl CoA
CITRIC
ACID
CYCLE
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The Evolutionary Significance of Glycolysis
Ancient prokaryotes are thought to have used
glycolysis long before there was oxygen in the
atmosphere
Very little O2 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
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Concept 9.6: 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
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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; amino
groups can feed glycolysis or the citric acid cycle
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Fats are digested to glycerol (used in glycolysis)
and fatty acids (used in generating acetyl CoA)
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
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Figure 9.19-1
Proteins Carbohydrates Fats
Amino
acids Sugars Glycerol Fatty
acids
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Figure 9.19-2
Proteins Carbohydrates Fats
Amino
acids Sugars Glycerol Fatty
acids
GLYCOLYSIS
Glucose
Glyceraldehyde 3- P
Pyruvate NH3
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Figure 9.19-3
Proteins Carbohydrates Fats
Amino
acids Sugars Glycerol Fatty
acids
GLYCOLYSIS
Glucose
Glyceraldehyde 3- P
Pyruvate
Acetyl CoA
NH3
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Figure 9.19-4
Proteins Carbohydrates Fats
Amino
acids Sugars Glycerol Fatty
acids
GLYCOLYSIS
Glucose
Glyceraldehyde 3- P
Pyruvate
Acetyl CoA
CITRIC
ACID
CYCLE
NH3
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Figure 9.19-5
Proteins Carbohydrates Fats
Amino
acids Sugars Glycerol Fatty
acids
GLYCOLYSIS
Glucose
Glyceraldehyde 3- P
Pyruvate
Acetyl CoA
CITRIC
ACID
CYCLE
OXIDATIVE
PHOSPHORYLATION
NH3
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Biosynthesis (Anabolic Pathways)
The body uses small molecules to build other
substances
These small molecules may come directly from
food, from glycolysis, or from the citric acid cycle
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Regulation of Cellular Respiration via Feedback Mechanisms
Feedback inhibition is the most common
mechanism for metabolic control
If ATP concentration begins to drop, respiration
speeds up; when there is plenty of ATP,
respiration slows down
Control of catabolism is based mainly on
regulating the activity of enzymes at strategic
points in the catabolic pathway
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Figure 9.20
Glucose
AMP
Stimulates
GLYCOLYSIS
Fructose 6-phosphate
Phosphofructokinase
Fructose 1,6-bisphosphate Inhibits Inhibits
Citrate
Pyruvate
Acetyl CoA ATP
CITRIC
ACID
CYCLE
Oxidative
phosphorylation
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Figure 9.UN10a
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Figure 9.UN10b
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Figure 9.UN11
Inputs Outputs
Glucose 2 Pyruvate 2 2 + + NADH ATP
GLYCOLYSIS
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Figure 9.UN12
Inputs Outputs
CITRIC
ACID
CYCLE
2 Pyruvate 2 Acetyl CoA
2 Oxaloacetate
2
2 6
8
FADH2
NADH ATP
CO2
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Figure 9.UN13
INTERMEMBRANE
SPACE
Protein complex
of electron
carriers
H+
H+ H+
2 H+ + ½ O2 H2O
MITOCHONDRIAL MATRIX
(carrying electrons from food)
NADH NAD+
FADH2
I
II
III
IV
Cyt c
Q
FAD
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Figure 9.UN14
INTER-
MEMBRANE
SPACE H+
MITOCHON-
DRIAL
MATRIX ATP
synthase
ADP + P i H+ ATP
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Figure 9.UN15
Low ATP
concentration
High ATP
concentration
Fructose 6-phosphate
concentration
Ph
osp
ho
fru
cto
kin
ase
acti
vit
y
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Figure 9.UN16
pH
dif
fere
nce
acro
ss m
em
bra
ne
Time
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Figure 9.UN17