biology in focus - chapter 7
TRANSCRIPT
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CAMPBELL BIOLOGY IN FOCUS
© 2014 Pearson Education, Inc.
Urry • Cain • Wasserman • Minorsky • Jackson • Reece
Lecture Presentations by Kathleen Fitzpatrick and Nicole Tunbridge
7Cellular Respiration and Fermentation
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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
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Figure 7.1
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Energy flows into an ecosystem as sunlight and leaves as heat
Photosynthesis generates O2 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
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Animation: Carbon Cycle
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Figure 7.2
Lightenergy
ECOSYSTEM
Photosynthesisin chloroplasts
CO2 H2OCellular respiration
in mitochondria
Organicmolecules O2
ATP ATP powersmost cellular work
Heatenergy
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Concept 7.1: Catabolic pathways yield energy by oxidizing organic fuels
Several processes are central to cellular respiration and related pathways
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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
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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)
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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)
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Figure 7.UN01
becomes oxidized(loses electron)
becomes reduced(gains electron)
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Figure 7.UN02
becomes oxidized
becomes reduced
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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 O2
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Figure 7.3
Reactants Products
Methane(reducing
agent)
Oxygen(oxidizing
agent)
Carbon dioxide Water
becomes reduced
becomes oxidized
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Redox reactions that move electrons closer to electronegative atoms, like oxygen, release chemical energy that can be put to work
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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
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
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Figure 7.UN03
becomes oxidized
becomes reduced
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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
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Figure 7.4
NAD
Nicotinamide(oxidized form)
Nicotinamide(reduced form)
Oxidation of NADH
Reduction of NAD
DehydrogenaseNADH
2[H] (from food)
2 e− 2 H
2 e− H
H
H
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Figure 7.4aNAD
Nicotinamide(oxidized form)
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Figure 7.4b
Nicotinamide(reduced form)
Oxidation of NADH
Reduction of NAD
DehydrogenaseNADH
2 e− 2 H
2 e− H
H
H 2[H] (from food)
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Figure 7.UN04
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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
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Figure 7.5
Explosiverelease
(a) Uncontrolled reaction (b) Cellular respiration
H2O
Free
ene
rgy,
G
Free
ene
rgy,
GElectron transport
chain
Controlledrelease of
energy
H2O
2 H
2 e−
2 H 2 e−
ATP
ATP
ATP
½
½
½H2 O2 O2
O2
2 H
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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)
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Animation: Cellular Respiration
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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 andchemiosmosis (color-coded violet)
2.
3.
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Figure 7.6-1
Electronsvia NADH
Glycolysis
Glucose Pyruvate
CYTOSOL
ATP
Substrate-level
MITOCHONDRION
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Figure 7.6-2
Electronsvia NADH
Glycolysis
Glucose Pyruvate
Pyruvateoxidation
Acetyl CoA
Citricacidcycle
Electronsvia NADH and
FADH2
CYTOSOL
ATP
Substrate-level
ATP
Substrate-level
MITOCHONDRION
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Figure 7.6-3
Electronsvia NADH
Glycolysis
Glucose Pyruvate
Pyruvateoxidation
Acetyl CoA
Citricacidcycle
Electronsvia NADH and
FADH2
Oxidativephosphorylation:electron transport
andchemiosmosis
CYTOSOL
ATP
Substrate-level
ATP
Substrate-level
MITOCHONDRION
ATP
Oxidative
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The process that generates most of the ATP is called oxidative phosphorylation because it is powered by redox reactions
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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
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Figure 7.7
SubstrateP
ADP
Product
ATP
Enzyme Enzyme
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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 O2 is present
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Figure 7.UN06
Glycolysis Pyruvateoxidation
Citricacidcycle
Oxidativephosphorylation
ATP ATP ATP
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Figure 7.8
Energy Investment Phase
Energy Payoff Phase
Net
Glucose
Glucose
2 ADP 2 P
4 ADP 4 P
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 H2O
2 Pyruvate 2 H2O
2 NADH 2 H
2 ATP
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Figure 7.9a
Glycolysis: Energy Investment Phase
GlucoseATP
ADP
Glucose6-phosphate
Phosphogluco-isomerase
Hexokinase
12 3
4
ATP
ADP
Fructose6-phosphate
Phospho-fructokinase
Fructose1,6-bisphosphate
Aldolase
Isomerase5
Glyceraldehyde3-phosphate (G3P)
Dihydroxyacetonephosphate (DHAP)
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Figure 7.9aa-1
Glycolysis: Energy Investment Phase
Glucose
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Figure 7.9aa-2
Glycolysis: Energy Investment Phase
GlucoseGlucose
6-phosphateADP
ATP
Hexokinase
1
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Figure 7.9aa-3
Glycolysis: Energy Investment Phase
GlucoseGlucose
6-phosphateADP
ATP
Hexokinase
1
Fructose6-phosphate
Phosphogluco-isomerase
2
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Figure 7.9ab-1
Glycolysis: Energy Investment Phase
Fructose6-phosphate
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Figure 7.9ab-2
Glycolysis: Energy Investment Phase
Fructose6-phosphate
Phospho-fructokinase
3
Fructose1,6-bisphosphate
ATP
ADP
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Figure 7.9ab-3
Glycolysis: Energy Investment Phase
Fructose6-phosphate
Phospho-fructokinase
3
Aldolase
Isomerase
4
5
Fructose1,6-bisphosphate
Glyceraldehyde3-phosphate (G3P)
ATP
ADP
Dihydroxyacetonephosphate (DHAP)
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Figure 7.9b
Glycolysis: Energy Payoff Phase
2 NADGlyceraldehyde
3-phosphate (G3P)
Triosephosphate
dehydrogenase
6
2 H
2 NADH
2
2 Pi
1,3-Bisphospho-glycerate
3-Phospho-glycerate
2-Phospho-glycerate
Phosphoenol-pyruvate (PEP)
Pyruvate
Phospho-glycerokinase
Phospho-glyceromutase
Enolase Pyruvatekinase
2 ADP 2 2 2 22 ADP
2 ATP2 H2O2 ATP
91087
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Figure 7.9ba-1
Isomerase
4
Glyceraldehyde3-phosphate (G3P)
Dihydroxyacetonephosphate (DHAP)
Glycolysis: Energy Payoff Phase
Aldolase5
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Figure 7.9ba-2
Isomerase
Glyceraldehyde3-phosphate (G3P)
Dihydroxyacetonephosphate (DHAP)
Glycolysis: Energy Payoff Phase
2 NAD
Triosephosphate
dehydrogenase
2 H
2 NADH
2
1,3-Bisphospho-glycerate
2
Aldolase
Pi
5 6
4
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Figure 7.9ba-3
Isomerase
Glyceraldehyde3-phosphate (G3P)
Dihydroxyacetonephosphate (DHAP)
Glycolysis: Energy Payoff Phase
2 NAD
Triosephosphate
dehydrogenase
2 H
2 NADH
2
1,3-Bisphospho-glycerate
3-Phospho-glycerate
Phospho-glycerokinase
2 ADP
2 ATP
2
Aldolase
Pi
2
5 76
4
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Figure 7.9bb-1
3-Phospho-glycerate
Glycolysis: Energy Payoff Phase
2
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Figure 7.9bb-2
83-Phospho-glycerate
Glycolysis: Energy Payoff Phase
Phospho-glyceromutase
2222 H2O
2-Phospho-glycerate
Phosphoenol-pyruvate (PEP)
Enolase
9
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Figure 7.9bb-3
3-Phospho-glycerate
Glycolysis: Energy Payoff Phase
2 ATP
Phospho-glyceromutase
22222 ADP2 H2O
2-Phospho-glycerate
Phosphoenol-pyruvate (PEP)
Pyruvate
Enolase Pyruvatekinase9
108
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Concept 7.3: 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
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
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Figure 7.UN07
Glycolysis Pyruvateoxidation
Citricacidcycle
Oxidativephosphorylation
ATP ATP ATP
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Figure 7.10CYTOSOLPyruvate
(from glycolysis,2 molecules per glucose)
CO2
CoANAD
NADH
MITOCHONDRION CoA
CoA
Acetyl CoA H
Citricacidcycle
FADH2
FAD
ADP Pi
ATP
NADH
3 NAD
3 3 H
2 CO2
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Figure 7.10a
CYTOSOLPyruvate(from glycolysis,2 molecules per glucose)
CO2
CoANAD
NADH
MITOCHONDRION CoAAcetyl CoA H
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Figure 7.10b
CoA
Citricacidcycle
FADH2
FAD
ADP Pi
ATP
NADH
3 NAD
3 3 H
2 CO2
CoAAcetyl CoA
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The citric acid cycle, also called the Krebs cycle, completes the breakdown of pyruvate to CO2
The cycle oxidizes organic fuel derived from pyruvate, generating 1 ATP, 3 NADH, and 1 FADH2 per turn
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Figure 7.UN08
Glycolysis Pyruvateoxidation
Oxidativephosphorylation
ATP ATP ATP
Citricacidcycle
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Figure 7.11-1
Acetyl CoA
Oxaloacetate
CoA-SH
Citrate
H2O
Isocitrate
Citricacidcycle
2
1
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Figure 7.11-2
Acetyl CoA
Oxaloacetate
Citrate
H2O
Isocitrate
NADHNAD
H
CO2
-Ketoglutarate
Citricacidcycle
3
1
CoA-SH
2
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Figure 7.11-3
Acetyl CoA
Oxaloacetate
Citrate
H2O
Isocitrate
NADHNAD
H
CO2
-Ketoglutarate
Citricacidcycle
CoA-SH
CO2NAD
NADH HSuccinyl
CoA
4
1
3
CoA-SH
2
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Figure 7.11-4
Acetyl CoA
Oxaloacetate
Citrate
H2O
Isocitrate
NADHNAD
H
CO2
-Ketoglutarate
Citricacidcycle
CoA-SH
CO2NAD
NADH H
ATP formation
SuccinylCoA
ADP
GDPGTP
Pi
ATP
Succinate
5
4
1
CoA-SH
3
CoA-SH
2
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Figure 7.11-5
Malate
SuccinateFAD
FADH2
Fumarate
H2O7
6
Acetyl CoA
Oxaloacetate
Citrate
H2O
Isocitrate
NADHNAD
H
CO2
-Ketoglutarate
Citricacidcycle
CoA-SH
CO2NAD
NADH H
ATP formation
SuccinylCoA
ADP
GDPGTP
Pi
ATP
5
4
1
CoA-SH
3
CoA-SH
2
![Page 62: Biology in Focus - Chapter 7](https://reader030.vdocuments.mx/reader030/viewer/2022033013/587a4cec1a28ab00148b6a4b/html5/thumbnails/62.jpg)
© 2014 Pearson Education, Inc.
Figure 7.11-6
NADH
NAD
H
8
Malate
SuccinateFAD
FADH2
Fumarate
H2O7
6
Acetyl CoA
Oxaloacetate
Citrate
H2O
Isocitrate
NADHNAD
H
CO2
-Ketoglutarate
Citricacidcycle
CoA-SH
CO2NAD
NADH H
ATP formation
SuccinylCoA
ADP
GDPGTP
Pi
ATP
5
4
1
CoA-SH
3
CoA-SH
2
![Page 63: Biology in Focus - Chapter 7](https://reader030.vdocuments.mx/reader030/viewer/2022033013/587a4cec1a28ab00148b6a4b/html5/thumbnails/63.jpg)
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Figure 7.11a
CoA-SH
Acetyl CoA
Start: Acetyl CoA adds itstwo-carbon group tooxaloacetate, producingcitrate; this is a highlyexergonic reaction.
Oxaloacetate
CitrateIsocitrate
H2O1
2
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© 2014 Pearson Education, Inc.
Figure 7.11b
Isocitrate Redox reaction:Isocitrate is oxidized;NAD is reduced.
Redox reaction:After CO2 release, the resultingfour-carbon molecule is oxidized(reducing NAD), then madereactive by addition of CoA.
CO2 release
CO2 release
-Ketoglutarate
SuccinylCoA
NAD
NADH H
CO2
CO2
CoA-SH
NAD
NADH H
3
4
![Page 65: Biology in Focus - Chapter 7](https://reader030.vdocuments.mx/reader030/viewer/2022033013/587a4cec1a28ab00148b6a4b/html5/thumbnails/65.jpg)
© 2014 Pearson Education, Inc.
Figure 7.11c
CoA-SH
Redox reaction:Succinate is oxidized;FAD is reduced.
Fumarate
SuccinateSuccinyl
CoA
ATP formation
ATP
ADP
GDPGTP
FAD
FADH2
Pi
5
6
![Page 66: Biology in Focus - Chapter 7](https://reader030.vdocuments.mx/reader030/viewer/2022033013/587a4cec1a28ab00148b6a4b/html5/thumbnails/66.jpg)
© 2014 Pearson Education, Inc.
Figure 7.11d
Redox reaction:Malate is oxidized;NAD is reduced.
Fumarate
Malate
Oxaloacetate
H2O
NAD
H
NADH
7
8
![Page 67: Biology in Focus - Chapter 7](https://reader030.vdocuments.mx/reader030/viewer/2022033013/587a4cec1a28ab00148b6a4b/html5/thumbnails/67.jpg)
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
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![Page 68: Biology in Focus - Chapter 7](https://reader030.vdocuments.mx/reader030/viewer/2022033013/587a4cec1a28ab00148b6a4b/html5/thumbnails/68.jpg)
Concept 7.4: 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
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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
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Figure 7.UN09
Glycolysis Pyruvateoxidation
Citricacidcycle
Oxidativephosphorylation:electron transportand chemiosmosis
ATP ATP ATP
![Page 71: Biology in Focus - Chapter 7](https://reader030.vdocuments.mx/reader030/viewer/2022033013/587a4cec1a28ab00148b6a4b/html5/thumbnails/71.jpg)
© 2014 Pearson Education, Inc.
Figure 7.12
Multiproteincomplexes
(originally fromNADH or FADH2)
Free
ene
rgy
(G) r
elat
ive
to O
2 (kc
al/m
ol)
50
40
30
20
10
0
NADH
NAD
FADH2
FAD
2
2
e−
e−
FMNFe•S Fe•S
Q
III
IIICyt b
Cyt c1
Fe•S
Cyt c IV
Cyt aCyt a3
2 e−
O22 H ½
H2O
![Page 72: Biology in Focus - Chapter 7](https://reader030.vdocuments.mx/reader030/viewer/2022033013/587a4cec1a28ab00148b6a4b/html5/thumbnails/72.jpg)
© 2014 Pearson Education, Inc.
Figure 7.12a
Multiproteincomplexes
Free
ene
rgy
(G) r
elat
ive
to O
2 (kc
al/m
ol)
50
40
30
20
10
NADH
NAD
FADH2
FAD
2
2
e−
e−
FMNFe•S Fe•S
Q
III
IIICyt b
Cyt c1
Fe•S
Cyt c IV
Cyt aCyt a3
2 e−
![Page 73: Biology in Focus - Chapter 7](https://reader030.vdocuments.mx/reader030/viewer/2022033013/587a4cec1a28ab00148b6a4b/html5/thumbnails/73.jpg)
© 2014 Pearson Education, Inc.
Figure 7.12b
30
20
10
0
Cyt c1
Cyt cIV
Cyt aCyt a3
2 e−
Free
ene
rgy
(G) r
elat
ive
to O
2 (kc
al/m
ol)
(originally fromNADH or FADH2)
2 H ½ O2
H2O
![Page 74: Biology in Focus - Chapter 7](https://reader030.vdocuments.mx/reader030/viewer/2022033013/587a4cec1a28ab00148b6a4b/html5/thumbnails/74.jpg)
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
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![Page 75: Biology in Focus - Chapter 7](https://reader030.vdocuments.mx/reader030/viewer/2022033013/587a4cec1a28ab00148b6a4b/html5/thumbnails/75.jpg)
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
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Video: ATP Synthase 3-D Side View
Video: ATP Synthase 3-D Top View
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Figure 7.13
INTERMEMBRANE SPACE
MITOCHONDRIAL MATRIX
Rotor
Internal rod
Catalytic knob
StatorH
ATP
ADP
Pi
![Page 78: Biology in Focus - Chapter 7](https://reader030.vdocuments.mx/reader030/viewer/2022033013/587a4cec1a28ab00148b6a4b/html5/thumbnails/78.jpg)
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
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![Page 79: Biology in Focus - Chapter 7](https://reader030.vdocuments.mx/reader030/viewer/2022033013/587a4cec1a28ab00148b6a4b/html5/thumbnails/79.jpg)
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Figure 7.UN09
Glycolysis Pyruvateoxidation
Citricacidcycle
Oxidativephosphorylation:electron transportand chemiosmosis
ATP ATP ATP
![Page 80: Biology in Focus - Chapter 7](https://reader030.vdocuments.mx/reader030/viewer/2022033013/587a4cec1a28ab00148b6a4b/html5/thumbnails/80.jpg)
© 2014 Pearson Education, Inc.
Figure 7.14
Proteincomplexof electron carriers
H
HH
H
Q
I
II
III
FADH2 FAD
NADNADH
(carrying electronsfrom food)
Electron transport chain
Oxidative phosphorylation
Chemiosmosis
ATPsynthase
H
ADP ATPPi
H2O2 H ½ O2
IV
Cyt c
1 2
![Page 81: Biology in Focus - Chapter 7](https://reader030.vdocuments.mx/reader030/viewer/2022033013/587a4cec1a28ab00148b6a4b/html5/thumbnails/81.jpg)
© 2014 Pearson Education, Inc.
Figure 7.14a
Proteincomplexof electron carriers
H
Q
I
II
III
FADH2FAD
NADNADH
(carrying electronsfrom food)
Electron transport chain
H2O2 H ½ O2
Cyt c
1
IV
HH
![Page 82: Biology in Focus - Chapter 7](https://reader030.vdocuments.mx/reader030/viewer/2022033013/587a4cec1a28ab00148b6a4b/html5/thumbnails/82.jpg)
© 2014 Pearson Education, Inc.
Figure 7.14b
ATPsynthase
Chemiosmosis2
H
H
ADP Pi
ATP
![Page 83: Biology in Focus - Chapter 7](https://reader030.vdocuments.mx/reader030/viewer/2022033013/587a4cec1a28ab00148b6a4b/html5/thumbnails/83.jpg)
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
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![Page 84: Biology in Focus - Chapter 7](https://reader030.vdocuments.mx/reader030/viewer/2022033013/587a4cec1a28ab00148b6a4b/html5/thumbnails/84.jpg)
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Figure 7.15
Electron shuttlesspan membrane
CYTOSOL2 NADH
2 NADH
2 FADH2
or
2 NADH
GlycolysisGlucose 2
Pyruvate
Pyruvateoxidation
2 Acetyl CoA
Citricacidcycle
6 NADH 2 FADH2
Oxidativephosphorylation:electron transport
andchemiosmosis
about 26 or 28 ATP 2 ATP 2 ATP
About30 or 32 ATPMaximum per glucose:
MITOCHONDRION
![Page 85: Biology in Focus - Chapter 7](https://reader030.vdocuments.mx/reader030/viewer/2022033013/587a4cec1a28ab00148b6a4b/html5/thumbnails/85.jpg)
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Figure 7.15a
Electron shuttlesspan membrane
2 NADH
2 FADH2
or
2 NADH
GlycolysisGlucose 2
Pyruvate
2 ATP
![Page 86: Biology in Focus - Chapter 7](https://reader030.vdocuments.mx/reader030/viewer/2022033013/587a4cec1a28ab00148b6a4b/html5/thumbnails/86.jpg)
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Figure 7.15b
2 NADH 6 NADH 2 FADH2
Citricacidcycle
Pyruvateoxidation
2 Acetyl CoA
2 ATP
![Page 87: Biology in Focus - Chapter 7](https://reader030.vdocuments.mx/reader030/viewer/2022033013/587a4cec1a28ab00148b6a4b/html5/thumbnails/87.jpg)
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Figure 7.15c
2 NADH
2 NADH 6 NADH 2 FADH2
2 FADH2
or
Oxidativephosphorylation:electron transport
andchemiosmosis
about 26 or 28 ATP
![Page 88: Biology in Focus - Chapter 7](https://reader030.vdocuments.mx/reader030/viewer/2022033013/587a4cec1a28ab00148b6a4b/html5/thumbnails/88.jpg)
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Figure 7.15d
Maximum per glucose: About30 or 32 ATP
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Concept 7.5: 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 fermentation or anaerobic respiration 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 from pyruvate, and the second step reduces acetaldehyde to ethanol
Alcohol fermentation by yeast is used in brewing, winemaking, and baking
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Animation: Fermentation Overview
![Page 93: Biology in Focus - Chapter 7](https://reader030.vdocuments.mx/reader030/viewer/2022033013/587a4cec1a28ab00148b6a4b/html5/thumbnails/93.jpg)
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Figure 7.16
2 ADP 2 2 ATPPi
Glucose Glycolysis
2 Pyruvate
2 CO22 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 2 Pi
Glucose
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Figure 7.16a
2 ADP 2 2 ATPPi
Glucose Glycolysis
2 Pyruvate
2 CO22 NADH
2 H
2 NAD
2 Ethanol
(a) Alcohol fermentation
2 Acetaldehyde
![Page 95: Biology in Focus - Chapter 7](https://reader030.vdocuments.mx/reader030/viewer/2022033013/587a4cec1a28ab00148b6a4b/html5/thumbnails/95.jpg)
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Figure 7.16b
2 ADP 2 2 ATPPi
Glucose Glycolysis
2 Pyruvate
2 NADH 2 H
2 NAD
(b) Lactic acid fermentation
2 Lactate
![Page 96: Biology in Focus - Chapter 7](https://reader030.vdocuments.mx/reader030/viewer/2022033013/587a4cec1a28ab00148b6a4b/html5/thumbnails/96.jpg)
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
The processes have different final electron acceptors: an organic molecule (such as pyruvate or acetaldehyde) in fermentation and O2 in cellular respiration
Cellular respiration produces 32 ATP per glucose molecule; fermentation produces 2 ATP per glucose molecule
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Obligate anaerobes carry out only 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 7.17Glucose
CYTOSOLGlycolysis
Pyruvate
O2 present: Aerobic cellular respiration
No O2 present:Fermentation
Ethanol,lactate, or
other products
Acetyl CoA
Citricacidcycle
MITOCHONDRION
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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 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
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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 and amino
groups must be removed before amino acids can feed glycolysis or the citric acid cycle
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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
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Figure 7.18-1Proteins
Aminoacids
Carbohydrates
Sugars
Fats
Glycerol Fattyacids
![Page 105: Biology in Focus - Chapter 7](https://reader030.vdocuments.mx/reader030/viewer/2022033013/587a4cec1a28ab00148b6a4b/html5/thumbnails/105.jpg)
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Figure 7.18-2Proteins
Aminoacids
Carbohydrates
Sugars
GlucoseGlycolysis
Glyceraldehyde 3-
Pyruvate
P
NH3
Fats
Glycerol Fattyacids
![Page 106: Biology in Focus - Chapter 7](https://reader030.vdocuments.mx/reader030/viewer/2022033013/587a4cec1a28ab00148b6a4b/html5/thumbnails/106.jpg)
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Figure 7.18-3Proteins
Aminoacids
Carbohydrates
Sugars
GlucoseGlycolysis
Glyceraldehyde 3-
Pyruvate
P
Acetyl CoA
NH3
Fats
Glycerol Fattyacids
![Page 107: Biology in Focus - Chapter 7](https://reader030.vdocuments.mx/reader030/viewer/2022033013/587a4cec1a28ab00148b6a4b/html5/thumbnails/107.jpg)
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Figure 7.18-4Proteins
Aminoacids
Carbohydrates
Sugars
GlucoseGlycolysis
Glyceraldehyde 3-
Pyruvate
P
Acetyl CoA
Citricacidcycle
NH3
Fats
Glycerol Fattyacids
![Page 108: Biology in Focus - Chapter 7](https://reader030.vdocuments.mx/reader030/viewer/2022033013/587a4cec1a28ab00148b6a4b/html5/thumbnails/108.jpg)
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Figure 7.18-5Proteins
Aminoacids
Carbohydrates
Sugars
GlucoseGlycolysis
Glyceraldehyde 3-
Pyruvate
P
Acetyl CoA
Citricacidcycle
NH3
Fats
Glycerol Fattyacids
Oxidativephosphorylation
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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
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Figure 7.UN10a
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Figure 7.UN10b
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Figure 7.UN11
Inputs
GlucoseGlycolysis
2 Pyruvate 2
Outputs
ATP NADH 2
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© 2014 Pearson Education, Inc.
Figure 7.UN12
Inputs
2 Pyruvate 2 Acetyl CoA
2 OxaloacetateCitricacidcycle
Outputs
ATP
CO2
2
6 2
8 NADH
FADH2
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Figure 7.UN13a
Proteincomplexof electroncarriers
INTERMEMBRANESPACE
MITOCHONDRIAL MATRIX(carrying electrons from food)
NADH NAD
FADH2 FAD
Cyt c
Q
I
II
III
IV
2 H ½O2 H2O
H
HH
![Page 115: Biology in Focus - Chapter 7](https://reader030.vdocuments.mx/reader030/viewer/2022033013/587a4cec1a28ab00148b6a4b/html5/thumbnails/115.jpg)
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Figure 7.UN13b
INTER-MEMBRANESPACE
MITO-CHONDRIALMATRIX
ATPsynthase
ATPADP H
H
Pi
![Page 116: Biology in Focus - Chapter 7](https://reader030.vdocuments.mx/reader030/viewer/2022033013/587a4cec1a28ab00148b6a4b/html5/thumbnails/116.jpg)
© 2014 Pearson Education, Inc.
Figure 7.UN14
Time
pH d
iffer
ence
acro
ss m
embr
ane