biology in focus - chapter 7

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

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



Figure 7.1

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


Animation: Carbon Cycle


Figure 7.2

Lightenergy

ECOSYSTEM

Photosynthesisin chloroplasts

CO2 H2OCellular respiration

in mitochondria

Organicmolecules O2

ATP ATP powersmost cellular work

Heatenergy

Concept 7.1: Catabolic pathways yield energy by oxidizing organic fuels

Several processes are central to cellular respiration and related pathways


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


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)


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


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)



Figure 7.UN01

becomes oxidized(loses electron)

becomes reduced(gains electron)


Figure 7.UN02

becomes oxidized

becomes reduced

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



Figure 7.3

Reactants Products

Methane(reducing

agent)

Oxygen(oxidizing

agent)

Carbon dioxide Water

becomes reduced

becomes oxidized

Redox reactions that move electrons closer to electronegative atoms, like oxygen, release chemical energy that can be put to work


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



Figure 7.UN03

becomes oxidized

becomes reduced

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



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


Figure 7.4aNAD

Nicotinamide(oxidized form)


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)


Figure 7.UN04

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



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

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)


Animation: Cellular Respiration


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.


Figure 7.6-1

Electronsvia NADH

Glycolysis

Glucose Pyruvate

CYTOSOL

ATP

Substrate-level

MITOCHONDRION


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


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

The process that generates most of the ATP is called oxidative phosphorylation because it is powered by redox reactions


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



Figure 7.7

SubstrateP

ADP

Product

ATP

Enzyme Enzyme

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



Figure 7.UN06

Glycolysis Pyruvateoxidation

Citricacidcycle

Oxidativephosphorylation

ATP ATP ATP


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


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)


Figure 7.9aa-1


Glucose


Figure 7.9aa-2


GlucoseGlucose

6-phosphateADP

ATP

Hexokinase

1


Figure 7.9aa-3


GlucoseGlucose

6-phosphateADP

ATP

Hexokinase

1

Fructose6-phosphate

Phosphogluco-isomerase

2


Figure 7.9ab-1


Fructose6-phosphate


Figure 7.9ab-2


Fructose6-phosphate


3


ATP

ADP


Figure 7.9ab-3


Fructose6-phosphate


3

Aldolase

Isomerase

4

5



ATP

ADP



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


Figure 7.9ba-1

Isomerase

4




Aldolase5


Figure 7.9ba-2

Isomerase




2 NAD

Triosephosphate

dehydrogenase

2 H

2 NADH

2


2

Aldolase

Pi

5 6

4


Figure 7.9ba-3

Isomerase




2 NAD

Triosephosphate

dehydrogenase

2 H

2 NADH

2


3-Phospho-glycerate

Phospho-glycerokinase

2 ADP

2 ATP

2

Aldolase

Pi

2

5 76

4


Figure 7.9bb-1

3-Phospho-glycerate


2


Figure 7.9bb-2

83-Phospho-glycerate



2222 H2O

2-Phospho-glycerate


Enolase

9


Figure 7.9bb-3

3-Phospho-glycerate


2 ATP


22222 ADP2 H2O

2-Phospho-glycerate


Pyruvate

Enolase Pyruvatekinase9

108

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



Figure 7.UN07


Citricacidcycle


ATP ATP ATP


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


Figure 7.10a

CYTOSOLPyruvate(from glycolysis,2 molecules per glucose)

CO2

CoANAD

NADH

MITOCHONDRION CoAAcetyl CoA H


Figure 7.10b

CoA

Citricacidcycle

FADH2

FAD

ADP Pi

ATP

NADH

3 NAD

3 3 H

2 CO2

CoAAcetyl CoA

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



Figure 7.UN08



ATP ATP ATP

Citricacidcycle


Figure 7.11-1

Acetyl CoA

Oxaloacetate

CoA-SH

Citrate

H2O

Isocitrate

Citricacidcycle

2

1


Figure 7.11-2

Acetyl CoA

Oxaloacetate

Citrate

H2O

Isocitrate

NADHNAD

H

CO2

-Ketoglutarate

Citricacidcycle

3

1

CoA-SH

2


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


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


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


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


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


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


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


Figure 7.11d

Redox reaction:Malate is oxidized;NAD is reduced.

Fumarate

Malate

Oxaloacetate

H2O

NAD

H

NADH

7

8

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


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


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



Figure 7.UN09


Citricacidcycle

Oxidativephosphorylation:electron transportand chemiosmosis

ATP ATP ATP


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


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−


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

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


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



Video: ATP Synthase 3-D Side View

Video: ATP Synthase 3-D Top View


Figure 7.13

INTERMEMBRANE SPACE

MITOCHONDRIAL MATRIX

Rotor

Internal rod

Catalytic knob

StatorH

ATP

ADP

Pi

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



Figure 7.UN09


Citricacidcycle

Oxidativephosphorylation:electron transportand chemiosmosis

ATP ATP ATP


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


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


Figure 7.14b

ATPsynthase

Chemiosmosis2

H

H

ADP Pi

ATP

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



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


andchemiosmosis

about 26 or 28 ATP 2 ATP 2 ATP

About30 or 32 ATPMaximum per glucose:

MITOCHONDRION


Figure 7.15a

Electron shuttlesspan membrane

2 NADH

2 FADH2

or

2 NADH

GlycolysisGlucose 2

Pyruvate

2 ATP


Figure 7.15b

2 NADH 6 NADH 2 FADH2

Citricacidcycle

Pyruvateoxidation

2 Acetyl CoA

2 ATP


Figure 7.15c

2 NADH

2 NADH 6 NADH 2 FADH2

2 FADH2

or


andchemiosmosis

about 26 or 28 ATP


Figure 7.15d

Maximum per glucose: About30 or 32 ATP

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


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


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


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


Animation: Fermentation Overview


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


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


Figure 7.16b

2 ADP 2 2 ATPPi

Glucose Glycolysis

2 Pyruvate

2 NADH 2 H

2 NAD

(b) Lactic acid fermentation

2 Lactate

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


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


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



Figure 7.17Glucose

CYTOSOLGlycolysis

Pyruvate

O2 present: Aerobic cellular respiration

No O2 present:Fermentation

Ethanol,lactate, or

other products

Acetyl CoA

Citricacidcycle

MITOCHONDRION

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


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


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


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



Figure 7.18-1Proteins

Aminoacids

Carbohydrates

Sugars

Fats

Glycerol Fattyacids



Aminoacids

Carbohydrates

Sugars

GlucoseGlycolysis

Glyceraldehyde 3-

Pyruvate

P

NH3

Fats

Glycerol Fattyacids



Aminoacids

Carbohydrates

Sugars

GlucoseGlycolysis

Glyceraldehyde 3-

Pyruvate

P

Acetyl CoA

NH3

Fats

Glycerol Fattyacids



Aminoacids

Carbohydrates

Sugars

GlucoseGlycolysis

Glyceraldehyde 3-

Pyruvate

P

Acetyl CoA

Citricacidcycle

NH3

Fats

Glycerol Fattyacids

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



Figure 7.UN10a


Figure 7.UN10b


Figure 7.UN11

Inputs

GlucoseGlycolysis

2 Pyruvate 2

Outputs

ATP NADH 2


Figure 7.UN12

Inputs

2 Pyruvate 2 Acetyl CoA

2 OxaloacetateCitricacidcycle

Outputs

ATP

CO2

2

6 2

8 NADH

FADH2


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


Figure 7.UN13b

INTER-MEMBRANESPACE

MITO-CHONDRIALMATRIX

ATPsynthase

ATPADP H

H

Pi


Figure 7.UN14

Time

pH d

iffer

ence

acro

ss m

embr

ane

biology in focus - chapter 7

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