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Introduction
 In eukaryotes, cellular respiration
– harvests energy from food,
– yields large amounts of ATP, and
– Uses ATP to drive cellular work.
 A similar process takes place in many prokaryotic
organisms.
© 2012 Pearson Education, Inc.
Figure 6.0_1
Chapter 6: Big Ideas
Cellular Respiration:
Aerobic Harvesting
of Energy
Fermentation: Anaerobic
Harvesting of Energy
Stages of Cellular
Respiration
Connections Between
Metabolic Pathways
6.1 Photosynthesis and cellular respiration
provide energy for life
 Life requires energy.
 In almost all ecosystems, energy ultimately comes
from the sun.
 In photosynthesis,
– some of the energy in sunlight is captured by
chloroplasts,
– atoms of carbon dioxide and water are rearranged, and
– glucose and oxygen are produced.
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Figure 6.1
Sunlight energy
ECOSYSTEM
Photosynthesis
in chloroplasts
CO2
Glucose
H2O
O2
Cellular respiration
in mitochondria
(for cellular
work)
ATP
Heat energy
Figure 6.2
O2
Breathing
CO2
Lungs
CO2
Bloodstream
O2
Muscle cells carrying out
Cellular Respiration
Glucose  O2
CO2  H2O  ATP
Figure 6.3
C6H12O6
6
Glucose
Oxygen
O2
6 CO2
Carbon
dioxide
6
H2O
ATP
Water
 Heat
6.5 Cells tap energy from electrons “falling”
from organic fuels to oxygen
 Energy can be released from glucose by simply
burning it.
 The energy is dissipated as heat and light and is
not available to living organisms.
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6.5 Cells tap energy from electrons “falling”
from organic fuels to oxygen
 The movement of electrons from one molecule to
another is an oxidation-reduction reaction, or
redox reaction. In a redox reaction,
– the loss of electrons from one substance is called
oxidation,
– the addition of electrons to another substance is called
reduction,
– a molecule is oxidized when it loses one or more
electrons, and
– reduced when it gains one or more electrons.
© 2012 Pearson Education, Inc.
Figure 6.5A
Loss of hydrogen atoms
(becomes oxidized)
C6H12O6
6 O2
6 CO2
6 H2O
Glucose
Gain of hydrogen atoms
(becomes reduced)
ATP
 Heat
Figure 6.5C
NADH
NAD
ATP
2
Controlled
release of
energy for
synthesis
of ATP
H
2
1 O
2 2
2 H
H 2O
6.6 Overview: Cellular respiration occurs in
three main stages
 Cellular respiration consists of a sequence of steps
that can be divided into three stages.
– Stage 1 – Glycolysis
– Stage 2 – Pyruvate oxidation and citric acid cycle
– Stage 3 – Oxidative phosphorylation
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6.6 Overview: Cellular respiration occurs in
three main stages
 Stage 1: Glycolysis
– occurs in the cytoplasm,
– begins cellular respiration, and
– breaks down glucose into two molecules of a threecarbon compound called pyruvate.
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6.6 Overview: Cellular respiration occurs in
three main stages
 Stage 2: The citric acid cycle
– takes place in mitochondria,
– oxidizes pyruvate to a two-carbon compound, and
– supplies the third stage with electrons.
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6.6 Overview: Cellular respiration occurs in
three main stages
 Stage 3: Oxidative phosphorylation
– involves electrons carried by NADH and FADH2,
– shuttles these electrons to the electron transport chain
embedded in the inner mitochondrial membrane,
– involves chemiosmosis, and
– generates ATP through oxidative phosphorylation
associated with chemiosmosis.
© 2012 Pearson Education, Inc.
Figure 6.6_1
CYTOPLASM
NADH
Electrons
carried by NADH
NADH
Glycolysis
Pyruvate
Glucose
Pyruvate
Oxidation
Citric Acid
Cycle
FADH2
Oxidative
Phosphorylation
(electron transport
and chemiosmosis)
Mitochondrion
ATP
ATP
ATP
Substrate-level
phosphorylation
Substrate-level
phosphorylation
Oxidative
phosphorylation
Figure 6.7Ca_s1
Steps 1 – 3 A fuel
molecule is energized,
using ATP.
Glucose
ATP
Step
ENERGY
INVESTMENT
PHASE
1
ADP
P
Glucose 6-phosphate
P
Fructose 6-phosphate
P
Fructose
1,6-bisphosphate
2
ATP
3
ADP
P
Figure 6.7Ca_s2
Steps 1 – 3 A fuel
molecule is energized,
using ATP.
Glucose
ATP
Step
ENERGY
INVESTMENT
PHASE
1
ADP
P
Glucose 6-phosphate
P
Fructose 6-phosphate
P
Fructose
1,6-bisphosphate
2
ATP
3
ADP
Step 4 A six-carbon
intermediate splits
into two three-carbon
intermediates.
P
4
P
P
Glyceraldehyde
3-phosphate (G3P)
Figure 6.7Cb_s1
Step 5
A redox reaction
generates NADH.
NAD
NAD
5
P
NADH
ENERGY
PAYOFF
PHASE
P
P
H
5
P
NADH
H
P
P
P
P
1,3-Bisphosphoglycerate
Figure 6.7Cb_s2
Step 5
A redox reaction
generates NADH.
NAD
NAD
5
P
NADH
5
P
NADH
H
H
P
P
P
ADP
Steps 6 – 9
ATP and pyruvate
are produced.
ENERGY
PAYOFF
PHASE
P
P
P
1,3-Bisphosphoglycerate
P
3-Phosphoglycerate
ADP
6
6
ATP
ATP
P
7
7
P
P
2-Phosphoglycerate
8
H2O
P
P
ADP
Phosphoenolpyruvate (PEP)
ADP
9
9
ATP
8
H2O
ATP
Pyruvate
Figure 6.8
NAD
NADH
H
2
CoA
Pyruvate
Acetyl coenzyme A
1
CO2
3
Coenzyme A
Figure 6.9A
Acetyl CoA
CoA
CoA
2 CO2
Citric Acid Cycle
3 NAD
FADH2
3 NADH
FAD
3 H
ATP
ADP
P
Figure 6.9B_s3
Acetyl CoA
CoA
CoA
2 carbons enter cycle
Oxaloacetate
1
Citrate
NADH
H
NAD
5
NAD
NADH
2
H
Citric Acid Cycle
CO2 leaves cycle
Malate
FADH2
Alpha-ketoglutarate
4
3
FAD
CO2 leaves cycle
NAD
Succinate
ADP
Step 1
Acetyl CoA stokes
the furnace.
P
Steps 2 – 3
ATP
NADH, ATP, and CO2
are generated during redox reactions.
NADH
H
Steps 4 – 5
Further redox reactions generate
FADH2 and more NADH.
Figure 6.10_1
H
H
H
H
H Mobile
electron
carriers
Protein
complex
of electron
carriers
H
H
H
III
H ATP
synthase
IV
I
II
FADH2
Electron
flow
NADH
NAD
FAD
2 H
1
O
2 2
H2O
H
ADP
P
ATP
H
Electron Transport Chain
Oxidative Phosphorylation
Chemiosmosis
6.12 Review: Each molecule of glucose yields
many molecules of ATP
 Recall that the energy payoff of cellular respiration
involves
1. glycolysis,
2. alteration of pyruvate,
3. the citric acid cycle, and
4. oxidative phosphorylation.
© 2012 Pearson Education, Inc.
Figure 6.12
CYTOPLASM
Electron shuttles
across membrane
2 NADH
Mitochondrion
2 NADH
or
2 FADH2
6 NADH
2 NADH
Glycolysis
2
Pyruvate
Glucose
Pyruvate
Oxidation
2 Acetyl
CoA
Citric Acid
Cycle
2 FADH2
Oxidative
Phosphorylation
(electron transport
and chemiosmosis)
Maximum
per glucose:
2
ATP
by substrate-level
phosphorylation
2
ATP
by substrate-level
phosphorylation
 about
28 ATP
by oxidative
phosphorylation
About
32 ATP
Animation: Fermentation Overview
Right click on animation / Click play
© 2012 Pearson Education, Inc.
Figure 6.13A
2 ADP
2 P
2 ATP
Glycolysis
Glucose
2 NAD
2 NADH
2 Pyruvate
2 NADH
2 NAD
2 Lactate
Figure 6.13B
Glucose
2 NAD
Glycolysis
2 ADP
2 P
2 ATP
2 NADH
2 Pyruvate
2 NADH
2 CO2
2 NAD
2 Ethanol
6.14 EVOLUTION CONNECTION: Glycolysis
evolved early in the history of life on Earth
 The ancient history of glycolysis is supported by its
– occurrence in all the domains of life and
– location within the cell, using pathways that do not
involve any membrane-bounded organelles.
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CONNECTIONS BETWEEN
METABOLIC PATHWAYS
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6.15 Cells use many kinds of organic molecules
as fuel for cellular respiration
 Although glucose is considered to be the primary
source of sugar for respiration and fermentation,
ATP is generated using
– carbohydrates,
– fats, and
– proteins.
© 2012 Pearson Education, Inc.
Figure 6.15
Food, such as
peanuts
Carbohydrates
Sugars
Fats
Proteins
Glycerol Fatty acids
Amino acids
Amino
groups
Glucose
G3P
Pyruvate
Glycolysis
Pyruvate
Oxidation
Acetyl CoA
ATP
Citric
Acid
Cycle
Oxidative
Phosphorylation
Figure 6.16
ATP needed
to drive
biosynthesis
Citric
Acid
Cycle
ATP
Pyruvate
Oxidation
Acetyl CoA
Glucose Synthesis
Pyruvate
G3P
Glucose
Amino
groups
Amino acids
Proteins
Fatty acids Glycerol
Fats
Cells, tissues, organisms
Sugars
Carbohydrates
You should now be able to
1. Compare the processes and locations of cellular
respiration and photosynthesis.
2. Explain how breathing and cellular respiration are
related.
3. Provide the overall chemical equation for cellular
respiration.
4. Explain how the human body uses its daily supply
of ATP.
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You should now be able to
5. Explain how the energy in a glucose molecule is
released during cellular respiration.
6. Explain how redox reactions are used in cellular
respiration.
7. Describe the general roles of dehydrogenase,
NADH, and the electron transport chain in cellular
respiration.
8. Compare the reactants, products, and energy
yield of the three stages of cellular respiration.
© 2012 Pearson Education, Inc.
You should now be able to
9. Explain how rotenone, cyanide, carbon
monoxide, oligomycin, and uncouplers interrupt
critical events in cellular respiration.
10. Compare the reactants, products, and energy
yield of alcohol and lactic acid fermentation.
11. Distinguish between strict anaerobes and
facultative anaerobes.
12. Explain how carbohydrates, fats, and proteins
are used as fuel for cellular respiration.
© 2012 Pearson Education, Inc.
Figure 6.UN01
CYTOPLASM
Mitochondrion
NADH
Electrons
carried by NADH
Glycolysis
Glucose
Pyruvate
Pyruvate
Oxidation
Substratelevel
ATP phosphorylation
NADH FADH2
Citric
Acid
Cycle
Oxidative
Phosphorylation
(electron transport
and chemiosmosis)
SubstrateATP
level
ATP phosphorylation
Oxidative
phosphorylation
Figure 6.UN02
Cellular
respiration
has three stages
generates
oxidizes
uses
produce
some
produces
many
energy for
glucose and
organic fuels
(a)
(b)
(d)
to pull
electrons down
(c)
cellular work
(f)
by a process called
chemiosmosis
uses
(g)
H diffuse
through
ATP synthase (e)
uses
pumps H to create
H gradient
to