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CAMPBELL
BIOLOGY
TENTH
EDITION
Reece • Urry • Cain • Wasserman •
Minorsky • Jackson
10
Cell
Respiration
Lecture Presentation by
Nicole Tunbridge and
Kathleen Fitzpatrick
© 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 10.1
© 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 10.2
Light
energy
ECOSYSTEM
CO2 + H2O
Photosynthesis
in chloroplasts
Cellular respiration
in mitochondria
ATP
Heat
energy
© 2014 Pearson Education, Inc.
Organic
O
molecules + 2
ATP powers
most cellular work
BioFlix: The Carbon Cycle
© 2014 Pearson Education, Inc.
Concept 10.1: 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
© 2014 Pearson Education, Inc.
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 10.UN01
becomes oxidized
(loses electron)
becomes reduced
(gains electron)
© 2014 Pearson Education, Inc.
Figure 10.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
© 2014 Pearson Education, Inc.
Figure 10.3
Reactants
Products
becomes oxidized
becomes reduced
Methane
(reducing
agent)
© 2014 Pearson Education, Inc.
Oxygen
(oxidizing
agent)
Carbon dioxide
Water
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 10.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 10.4
2 e− + 2 H+
NAD+
2 e− + H+
Dehydrogenase
NADH
H+
Reduction of NAD+
2[H]
(from food) Oxidation of NADH
Nicotinamide
(oxidized form)
© 2014 Pearson Education, Inc.
H+
Nicotinamide
(reduced form)
Figure 10.4a
NAD+
Nicotinamide
(oxidized form)
© 2014 Pearson Education, Inc.
Figure 10.4b
2 e− + 2 H+
2 e− + H+
Dehydrogenase
NADH
H+
Reduction of NAD+
2[H]
(from food) Oxidation of NADH
H+
Nicotinamide
(reduced form)
© 2014 Pearson Education, Inc.
Figure 10.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 energyyielding tumble
§  The energy yielded is used to regenerate ATP
© 2014 Pearson Education, Inc.
Figure 10.5
H2 + ½ O2
2H
Free energy, G
rt
spo
tran
tron n
chai
Explosive
release
Controlled
release of
energy
Elec
Free energy, G
2 H+ + 2 e−
½ O2
+
ATP
ATP
ATP
2 e−
½ O2
2 H+
H 2O
(a) Uncontrolled reaction
© 2014 Pearson Education, Inc.
H 2O
(b) Cellular respiration
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 10.UN05
1. GLYCOLYSIS (color-coded blue throughout the chapter)
2. PYRUVATE OXIDATION and the CITRIC ACID CYCLE
(color-coded orange)
3. OXIDATIVE PHOSPHORYLATION: Electron transport and
chemiosmosis (color-coded purple)
© 2014 Pearson Education, Inc.
Figure 10.6-1
Electrons
via NADH
GLYCOLYSIS
Glucose
Pyruvate
CYTOSOL
ATP
Substrate-level
© 2014 Pearson Education, Inc.
MITOCHONDRION
Figure 10.6-2
Electrons
via NADH
GLYCOLYSIS
Glucose
Electrons
via NADH
and FADH2
PYRUVATE
OXIDATION
CITRIC
ACID
CYCLE
Pyruvate
Acetyl CoA
CYTOSOL
MITOCHONDRION
ATP
ATP
Substrate-level
Substrate-level
© 2014 Pearson Education, Inc.
Figure 10.6-3
Electrons
via NADH
GLYCOLYSIS
Glucose
Electrons
via NADH
and FADH2
PYRUVATE
OXIDATION
CITRIC
ACID
CYCLE
Pyruvate
Acetyl CoA
CYTOSOL
MITOCHONDRION
ATP
ATP
Substrate-level
Substrate-level
© 2014 Pearson Education, Inc.
OXIDATIVE
PHOSPHORYLATION
(Electron transport
and chemiosmosis)
ATP
Oxidative
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
100% 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 10.7
Enzyme
Enzyme
ADP
P
ATP
Substrate
Product
© 2014 Pearson Education, Inc.
Concept 10.2: 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 10.UN06
GLYCOLYSIS
ATP
© 2014 Pearson Education, Inc.
PYRUVATE
OXIDATION
CITRIC
ACID
CYCLE
OXIDATIVE
PHOSPHORYLATION
Figure 10.8
Energy Investment Phase
Glucose
2
ATP used
2 ADP + 2 P
Energy Payoff Phase
4 ADP + 4 P
2 NAD+ + 4 e− + 4 H+
4
ATP
formed
2 NADH + 2 H+
2 Pyruvate + 2 H2O
Net
Glucose
4 ATP formed − 2 ATP used
2 NAD+ + 4 e− + 4 H+
© 2014 Pearson Education, Inc.
2 Pyruvate + 2 H2O
2 ATP
2 NADH + 2 H+
Figure 10.9a
GLYCOLYSIS: Energy Investment Phase
Glyceraldehyde
3-phosphate (G3P)
Glucose
ATP
ADP
Fructose ATP
6-phosphate
ADP
Glucose
6-phosphate
Fructose
1,6-bisphosphate
Isomerase
Hexokinase
1
© 2014 Pearson Education, Inc.
Phosphoglucoisomerase
Phosphofructokinase
2
3
Aldolase
4
5
Dihydroxyacetone
phosphate (DHAP)
Figure 10.9aa-1
GLYCOLYSIS: Energy Investment Phase
Glucose
© 2014 Pearson Education, Inc.
Figure 10.9aa-2
GLYCOLYSIS: Energy Investment Phase
Glucose
Glucose
6-phosphate
ATP
ADP
Hexokinase
1
© 2014 Pearson Education, Inc.
Figure 10.9aa-3
GLYCOLYSIS: Energy Investment Phase
Glucose
Glucose
6-phosphate
ATP
ADP
Hexokinase
1
© 2014 Pearson Education, Inc.
Fructose
6-phosphate
Phosphoglucoisomerase
2
Figure 10.9ab-1
GLYCOLYSIS: Energy Investment Phase
Fructose
6-phosphate
© 2014 Pearson Education, Inc.
Figure 10.9ab-2
GLYCOLYSIS: Energy Investment Phase
Fructose ATP
6-phosphate
ADP
Phosphofructokinase
3
© 2014 Pearson Education, Inc.
Fructose
1,6-bisphosphate
Figure 10.9ab-3
GLYCOLYSIS: Energy Investment Phase
Glyceraldehyde
3-phosphate (G3P)
Fructose ATP
6-phosphate
ADP
Fructose
1,6-bisphosphate
Isomerase
Phosphofructokinase
3
© 2014 Pearson Education, Inc.
Aldolase
4
5
Dihydroxyacetone
phosphate (DHAP)
Figure 10.9b
GLYCOLYSIS: Energy Payoff Phase
2 NADH
+
2 NAD + 2 H+
2
Triose
phosphate 2
dehydrogenase
Glyceraldehyde
3-phosphate
(G3P)
6
© 2014 Pearson Education, Inc.
2 ATP
2 ADP
2
2
Phosphoglycerokinase
Phosphoglyceromutase
1,3-Bisphosphoglycerate
7
3-Phosphoglycerate
8
2-Phosphoglycerate
2 H 2O
2
Enolase
10
2 ATP
2 ADP
2
Pyruvate
kinase
10
Phosphoenolpyruvate (PEP)
Pyruvate
Figure 10.9ba-1
GLYCOLYSIS: Energy Payoff Phase
Glyceraldehyde
3-phosphate (G3P)
Isomerase
5
Aldolase
4
Dihydroxyacetone
phosphate (DHAP)
© 2014 Pearson Education, Inc.
Figure 10.9ba-2
GLYCOLYSIS: Energy Payoff Phase
Glyceraldehyde
3-phosphate (G3P)
Aldolase
4
Isomerase
Triose
phosphate 2
dehydrogenase
5
6
Dihydroxyacetone
phosphate (DHAP)
© 2014 Pearson Education, Inc.
2 NADH
2 NAD+
2 H+
2
1,3-Bisphosphoglycerate
Figure 10.9ba-3
GLYCOLYSIS: Energy Payoff Phase
Glyceraldehyde
3-phosphate (G3P)
Aldolase
4
Isomerase
Triose
phosphate 2
dehydrogenase
5
6
Dihydroxyacetone
phosphate (DHAP)
© 2014 Pearson Education, Inc.
2 NADH
2 NAD+
2 H+
2
2 ATP
2 ADP
2
Phosphoglycerokinase
1,3-Bisphosphoglycerate
7
3-Phosphoglycerate
Figure 10.9bb-1
GLYCOLYSIS: Energy Payoff Phase
2
3-Phosphoglycerate
© 2014 Pearson Education, Inc.
Figure 10.9bb-2
GLYCOLYSIS: Energy Payoff Phase
2
2
Phosphoglyceromutase
3-Phosphoglycerate
© 2014 Pearson Education, Inc.
8
2-Phosphoglycerate
2 H 2O
2
Enolase
10
Phosphoenolpyruvate (PEP)
Figure 10.9bb-3
GLYCOLYSIS: Energy Payoff Phase
2
2
Phosphoglyceromutase
3-Phosphoglycerate
© 2014 Pearson Education, Inc.
8
2-Phosphoglycerate
2 H 2O
2
Enolase
10
2 ATP
2 ADP
2
Pyruvate
kinase
10
Phosphoenolpyruvate (PEP)
Pyruvate
Concept 10.3: 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 10.UN07
GLYCOLYSIS
© 2014 Pearson Education, Inc.
PYRUVATE
OXIDATION
CITRIC
ACID
CYCLE
OXIDATIVE
PHOSPHORYLATION
Figure 10.10
MITOCHONDRION
CYTOSOL
CO2
Coenzyme A
3
1
2
Pyruvate
Transport protein
© 2014 Pearson Education, Inc.
NAD+
NADH + H+
Acetyl CoA
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 10.11
PYRUVATE OXIDATION
Pyruvate (from glycolysis,
2 molecules per glucose)
CO2
NAD+
CoA
NADH
+ H+
Acetyl CoA
CoA
CoA
CITRIC
ACID
CYCLE
FADH2
2 CO2
3 NAD+
CoA
FAD
3 NADH
+ 3 H+
ADP + P i
ATP
© 2014 Pearson Education, Inc.
Figure 10.11a
PYRUVATE OXIDATION
Pyruvate (from glycolysis,
2 molecules per glucose)
CO2
NAD+
CoA
NADH
+ H+
Acetyl CoA
CoA
© 2014 Pearson Education, Inc.
Figure 10.11b
Acetyl CoA
CoA
CoA
CITRIC
ACID
CYCLE
FADH2
2 CO2
3 NAD+
3 NADH
FAD
+ 3 H+
ADP + P i
ATP
© 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 10.UN08
GLYCOLYSIS
PYRUVATE
OXIDATION
CITRIC
ACID
CYCLE
ATP
© 2014 Pearson Education, Inc.
OXIDATIVE
PHOSPHORYLATION
Figure 10.12-1
Acetyl CoA
CoA-SH
1
Oxaloacetate
Citrate
CITRIC
ACID
CYCLE
© 2014 Pearson Education, Inc.
Figure 10.12-2
Acetyl CoA
CoA-SH
H 2O
1
Oxaloacetate
2
Citrate
CITRIC
ACID
CYCLE
© 2014 Pearson Education, Inc.
Isocitrate
Figure 10.12-3
Acetyl CoA
CoA-SH
H 2O
1
Oxaloacetate
2
Citrate
CITRIC
ACID
CYCLE
Isocitrate
NAD+
3
NADH
+ H+
CO2
α-Ketoglutarate
© 2014 Pearson Education, Inc.
Figure 10.12-4
Acetyl CoA
CoA-SH
H 2O
1
Oxaloacetate
2
Citrate
Isocitrate
NAD+
CITRIC
ACID
CYCLE
NADH
+ H+
3
CO2
CoA-SH
4
NAD+
NADH
Succinyl
CoA
© 2014 Pearson Education, Inc.
+ H+
α-Ketoglutarate
CO2
Figure 10.12-5
Acetyl CoA
CoA-SH
H 2O
1
Oxaloacetate
2
Citrate
Isocitrate
NAD+
CITRIC
ACID
CYCLE
NADH
+ H+
3
CO2
CoA-SH
4
α-Ketoglutarate
CoA-SH
5
Succinate
Pi
GTP GDP
ADP
ATP
© 2014 Pearson Education, Inc.
NAD+
Succinyl
CoA
NADH
+ H+
CO2
Figure 10.12-6
Acetyl CoA
CoA-SH
H 2O
1
Oxaloacetate
2
Citrate
Isocitrate
NAD+
CITRIC
ACID
CYCLE
Fumarate
CO2
CoA-SH
4
6
α-Ketoglutarate
CoA-SH
5
FADH2
NAD+
FAD
Succinate
Pi
GTP GDP
ADP
ATP
© 2014 Pearson Education, Inc.
NADH
+ H+
3
Succinyl
CoA
NADH
+ H+
CO2
Figure 10.12-7
Acetyl CoA
CoA-SH
H 2O
1
Oxaloacetate
2
Malate
H 2O
Citrate
NAD+
CITRIC
ACID
CYCLE
7
Fumarate
NADH
+ H+
3
CO2
CoA-SH
4
6
α-Ketoglutarate
CoA-SH
5
FADH2
NAD+
FAD
Succinate
Pi
GTP GDP
ADP
ATP
© 2014 Pearson Education, Inc.
Isocitrate
Succinyl
CoA
NADH
+ H+
CO2
Figure 10.12-8
Acetyl CoA
CoA-SH
NADH
+ H+
H 2O
1
NAD+
Oxaloacetate
8
2
Malate
H 2O
Citrate
NAD+
CITRIC
ACID
CYCLE
7
Fumarate
NADH
+ H+
3
CO2
CoA-SH
4
6
α-Ketoglutarate
CoA-SH
5
FADH2
NAD+
FAD
Succinate
Pi
GTP GDP
ADP
ATP
© 2014 Pearson Education, Inc.
Isocitrate
Succinyl
CoA
NADH
+ H+
CO2
Figure 10.12a
Acetyl CoA
CoA-SH
H 2O
1
Oxaloacetate
2
Citrate
© 2014 Pearson Education, Inc.
Isocitrate
Figure 10.12b
Isocitrate
NAD+
NADH
+ H+
3
CO2
CoA-SH
4
NAD+
© 2014 Pearson Education, Inc.
Succinyl
CoA
NADH
+ H+
α-Ketoglutarate
CO2
Figure 10.12c
Fumarate
6
CoA-SH
FADH2
5
FAD
Pi
Succinate
GTP GDP
ADP
ATP
© 2014 Pearson Education, Inc.
Succinyl
CoA
Figure 10.12d
NADH
+ H+
NAD+
8
Oxaloacetate
Malate
H 2O
7
Fumarate
© 2014 Pearson Education, Inc.
Concept 10.4: 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 10.UN010
GLYCOLYSIS
PYRUVATE
OXIDATION
CITRIC
ACID
CYCLE
OXIDATIVE
PHOSPHORYLATION
ATP
© 2014 Pearson Education, Inc.
Figure 10.13
NADH
Free energy (G) relative to O2 (kcal/mol)
50
2 e− NAD+
FADH2
40
FMN
2 e−
FAD
Fe•S
II
I
Fe•S
Multiprotein
complexes
Q
III
Cyt b
30
Fe•S
Cyt c1
IV
Cyt c
Cyt a
20
10
0
Cyt a3
2 e−
(originally from
NADH or FADH2)
2 H+ + ½ O2
H 2O
© 2014 Pearson Education, Inc.
Figure 10.13a
Free energy (G) relative to O2 (kcal/mol)
NADH
© 2014 Pearson Education, Inc.
50
2 e−
NAD+
FADH2
40
FMN
2 e−
FAD
Fe•S
II
I
Fe•S
Q
III
Cyt b
30
Multiprotein
complexes
Fe•S
Cyt c1
IV
Cyt c
Cyt a
20
10
Cyt a3
2 e−
Free energy (G) relative to O2 (kcal/mol)
Figure 10.13b
© 2014 Pearson Education, Inc.
30
Cyt c1
IV
Cyt c
Cyt a
20
10
0
Cyt a3
2 e−
(originally from
NADH or FADH2)
2 H+ + ½ O2
H 2O
§  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 10.14
INTERMEMBRANE
H+
SPACE
Rotor
Stator
Internal rod
Catalytic
knob
ADP
+
Pi
MITOCHONDRIAL
MATRIX
© 2014 Pearson Education, Inc.
ATP
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 10.15
Protein
complex
of electron
carriers
H+
ATP
synthase
H+
H+
H+
Cyt c
IV
Q
III
I
II
FADH2 FAD
NADH
(carrying
electrons
from
food)
2 H+ + ½ O2
NAD+
H 2O
ADP + P i
H+
1 Electron transport chain
Oxidative phosphorylation
© 2014 Pearson Education, Inc.
ATP
2 Chemiosmosis
Figure 10.15a
Protein
complex
of electron
carriers
H+
H+
Cyt c
IV
Q
III
I
II
FADH2 FAD
NADH
(carrying
electrons
from
food)
© 2014 Pearson Education, Inc.
H+
2 H+ + ½ O2
NAD+
1 Electron transport chain
H 2O
Figure 10.15b
H+
ADP + P i
ATP
synthase
ATP
H+
2 Chemiosmosis
© 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 10.16
Electron shuttles
span membrane
CYTOSOL
2 NADH
2
Pyruvate
PYRUVATE
OXIDATION
2 Acetyl CoA
+ 2 ATP
Maximum per glucose:
© 2014 Pearson Education, Inc.
6 NADH
2 NADH
GLYCOLYSIS
Glucose
MITOCHONDRION
2 NADH
or
2 FADH2
2 FADH2
CITRIC
ACID
CYCLE
OXIDATIVE
PHOSPHORYLATION
(Electron transport
and chemiosmosis)
+ 2 ATP
+ about 26 or 28 ATP
About
30 or 32 ATP
Figure 10.16a
Electron shuttles
span membrane
2 NADH
GLYCOLYSIS
Glucose
2
Pyruvate
+ 2 ATP
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2 NADH
or
2 FADH2
Figure 10.16b
6 NADH
2 NADH
PYRUVATE
OXIDATION
2 Acetyl CoA
CITRIC
ACID
CYCLE
+ 2 ATP
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2 FADH2
Figure 10.16c
2 NADH
or
2 FADH2
2 NADH
6 NADH
2 FADH2
OXIDATIVE
PHOSPHORYLATION
(Electron transport
and chemiosmosis)
+ about 26 or 28 ATP
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Figure 10.16d
Maximum per glucose:
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About
30 or 32 ATP
Concept 10.5: 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 10.17
2 ADP + 2 P i
2
ATP
2 ADP + 2 P i
GLYCOLYSIS
Glucose
Glucose
2
ATP
GLYCOLYSIS
2 Pyruvate
2 NAD+
2 Ethanol
(a) Alcohol fermentation
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2 NADH
+ 2 H+
2 CO2
2 Acetaldehyde
2 NAD+
2 NADH
+ 2 H+
2 Lactate
(b) Lactic acid fermentation
2 Pyruvate
Figure 10.17a
2 ADP + 2 P i
Glucose
2
ATP
GLYCOLYSIS
2 Pyruvate
2 NAD+
2 NADH
+ 2 H+
2 Ethanol
(a) Alcohol fermentation
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2 CO2
2 Acetaldehyde
Figure 10.17b
2 ADP + 2 P i
Glucose
2
ATP
GLYCOLYSIS
2 NAD+
2 NADH
+ 2 H+
2 Lactate
(b) Lactic acid fermentation
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2 Pyruvate
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 10.18
Glucose
CYTOSOL
Glycolysis
Pyruvate
No O2 present:
Fermentation
O2 present:
Aerobic cellular
respiration
MITOCHONDRION
Ethanol,
lactate, or
other products
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Acetyl CoA
CITRIC
ACID
CYCLE
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 10.6: 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 10.19-1
Proteins
Carbohydrates
Amino
acids
Sugars
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Fats
Glycerol
Fatty
acids
Figure 10.19-2
Proteins
Carbohydrates
Amino
acids
Sugars
Fats
Glycerol
GLYCOLYSIS
Glucose
Glyceraldehyde 3- P
NH3
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Pyruvate
Fatty
acids
Figure 10.19-3
Proteins
Carbohydrates
Amino
acids
Sugars
Fats
Glycerol
GLYCOLYSIS
Glucose
Glyceraldehyde 3- P
NH3
Pyruvate
Acetyl CoA
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Fatty
acids
Figure 10.19-4
Proteins
Carbohydrates
Amino
acids
Sugars
Fats
Glycerol
GLYCOLYSIS
Glucose
Glyceraldehyde 3- P
NH3
Pyruvate
Acetyl CoA
CITRIC
ACID
CYCLE
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Fatty
acids
Figure 10.19-5
Proteins
Carbohydrates
Amino
acids
Sugars
Fats
Glycerol
Fatty
acids
GLYCOLYSIS
Glucose
Glyceraldehyde 3- P
NH3
Pyruvate
Acetyl CoA
CITRIC
ACID
CYCLE
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OXIDATIVE
PHOSPHORYLATION
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 10.20
Glucose
GLYCOLYSIS
Fructose 6-phosphate
AMP
Stimulates
Phosphofructokinase
Inhibits
Fructose 1,6-bisphosphate
Inhibits
Pyruvate
ATP
Citrate
Acetyl CoA
CITRIC
ACID
CYCLE
Oxidative
phosphorylation
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Figure 10.UN10a
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Figure 10.UN10b
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Figure 10.UN11
Outputs
Inputs
GLYCOLYSIS
Glucose
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2 Pyruvate + 2
ATP
+ 2 NADH
Figure 10.UN12
Inputs
2 Pyruvate
2 Acetyl CoA
2 Oxaloacetate
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Outputs
CITRIC
ACID
CYCLE
2
ATP
8 NADH
6
CO2
2 FADH2
Figure 10.UN13
H+
H+
IV
Q
III
I
II
FADH2 FAD
NAD+
(carrying electrons from food)
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H+
Cyt c
Protein complex
of electron
carriers
NADH
INTERMEMBRANE
SPACE
2 H+ + ½ O2
MITOCHONDRIAL MATRIX
H 2O
Figure 10.UN14
INTERMEMBRANE
SPACE
H+
MITOCHONDRIAL
MATRIX
ADP + P i
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ATP
synthase
H+
ATP
Phosphofructokinase
activity
Figure 10.UN15
Low ATP
concentration
High ATP
concentration
Fructose 6-phosphate
concentration
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pH difference
across membrane
Figure 10.UN16
Time
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Figure 10.UN17
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