Cellular Respiration and Fermentation

Chapter 9

LECTURE PRESENTATIONS

For CAMPBELL BIOLOGY, NINTH EDITION

Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson

© 2011 Pearson Education, Inc.

Lectures by

Erin Barley

Kathleen Fitzpatrick

Overview: Life Is Work

• Living cells require energy from outside sources
• Some animals, such as the chimpanzee, obtain energy by eating plants, and some animals feed on other organisms that eat plants

Figure 9.1

• 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 regenerate ATP, which powers work

Figure 9.2

Light�energy

ECOSYSTEM

Photosynthesis�in chloroplasts

Cellular respiration�in mitochondria

CO₂ + H₂O

ATP powers�most cellular work

ATP

Heat�energy

Concept 9.1: 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 9.UN01

becomes oxidized�(loses electron)

becomes reduced�(gains electron)

Figure 9.UN02

becomes oxidized

becomes reduced

• 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

​

Figure 9.3

Reactants

Products

Energy

Water

Carbon dioxide

Methane�(reducing�agent)

Oxygen�(oxidizing�agent)

becomes oxidized

becomes reduced

Oxidation of Organic Fuel Molecules During Cellular Respiration

• During cellular respiration, the fuel (such as glucose) is oxidized, and O₂ is reduced

Figure 9.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 9.4

Nicotinamide�(oxidized form)

NAD⁺

(from food)

Dehydrogenase

Reduction of NAD⁺

Oxidation of NADH

Nicotinamide�(reduced form)

NADH

Figure 9.UN04

Dehydrogenase

• 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 9.5

(a) Uncontrolled reaction

(b) Cellular respiration

Explosive�release of�heat and light�energy

Controlled�release of�energy for�synthesis of�ATP

Free energy, G

Free energy, G

H₂ + ¹/₂ O₂

2 H

+

¹/₂ O₂

¹/₂ O₂

H₂O

H₂O

2 H⁺ + 2 e⁻

2 e⁻

2 H⁺

ATP

ATP

ATP

Electron transport�chain

(from food via NADH)

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)

Figure 9.UN05

Figure 9.6-1

Electrons�carried�via NADH

Glycolysis

Glucose

Pyruvate

CYTOSOL

MITOCHONDRION

ATP

Substrate-level�phosphorylation

Figure 9.6-2

Electrons�carried�via NADH

Electrons carried�via NADH and�FADH₂

Citric�acid�cycle

Pyruvate�oxidation

Acetyl CoA

Glycolysis

Glucose

Pyruvate

CYTOSOL

MITOCHONDRION

ATP

ATP

Substrate-level�phosphorylation

Substrate-level�phosphorylation

Figure 9.6-3

Electrons�carried�via NADH

Electrons carried�via NADH and�FADH₂

Citric�acid�cycle

Pyruvate�oxidation

Acetyl CoA

Glycolysis

Glucose

Pyruvate

Oxidative�phosphorylation:�electron transport�and�chemiosmosis

CYTOSOL

MITOCHONDRION

ATP

ATP

ATP

Substrate-level�phosphorylation

Substrate-level�phosphorylation

Oxidative �phosphorylation

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

​

BioFlix: Cellular Respiration

• 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 9.7

Substrate

Product

ADP

P

ATP

Enzyme

Enzyme

Concept 9.2: Glycolysis harvests chemical energy by oxidizing glucose to pyruvate

• Glycolysis (“splitting of sugar”) 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 9.8

Energy Investment Phase

Glucose

2 ADP + 2 P

4 ADP + 4 P

Energy Payoff Phase

2 NAD⁺ + 4 e⁻ + 4 H⁺

2 Pyruvate + 2 H₂O

2 ATP used

4 ATP formed

2 NADH + 2 H⁺

Net

Glucose

2 Pyruvate + 2 H₂O

2 ATP

2 NADH + 2 H⁺

2 NAD⁺ + 4 e⁻ + 4 H⁺

4 ATP formed − 2 ATP used

Figure 9.9-1

Glycolysis: Energy Investment Phase

ATP

Glucose

Glucose 6-phosphate

ADP

Hexokinase

Figure 9.9-2

Glycolysis: Energy Investment Phase

ATP

Glucose

Glucose 6-phosphate

Fructose 6-phosphate

ADP

Hexokinase

Phosphogluco-�isomerase

Figure 9.9-3

Glycolysis: Energy Investment Phase

ATP

ATP

Glucose

Glucose 6-phosphate

Fructose 6-phosphate

Fructose 1,6-bisphosphate

ADP

ADP

Hexokinase

Phosphogluco-�isomerase

Phospho-�fructokinase

Figure 9.9-4

Glycolysis: Energy Investment Phase

ATP

ATP

Glucose

Glucose 6-phosphate

Fructose 6-phosphate

Fructose 1,6-bisphosphate

Dihydroxyacetone�phosphate

Glyceraldehyde�3-phosphate

To�step 6

ADP

ADP

Hexokinase

Phosphogluco-�isomerase

Phospho-�fructokinase

Aldolase

Isomerase

Figure 9.9-5

Glycolysis: Energy Payoff Phase

2 NADH

2 NAD⁺

+ 2 H⁺

2 P _i

1,3-Bisphospho-�glycerate

Triose�phosphate�dehydrogenase

Figure 9.9-6

Glycolysis: Energy Payoff Phase

2 ATP

2 NADH

2 NAD⁺

+ 2 H⁺

2 P _i

2 ADP

1,3-Bisphospho-�glycerate

3-Phospho-�glycerate

2

Phospho-�glycerokinase

Triose�phosphate�dehydrogenase

Figure 9.9-7

Glycolysis: Energy Payoff Phase

2 ATP

2 NADH

2 NAD⁺

+ 2 H⁺

2 P _i

2 ADP

1,3-Bisphospho-�glycerate

3-Phospho-�glycerate

2-Phospho-�glycerate

2

2

Phospho-�glycerokinase

Phospho-�glyceromutase

Triose�phosphate�dehydrogenase

Figure 9.9-8

Glycolysis: Energy Payoff Phase

2 ATP

2 NADH

2 NAD⁺

+ 2 H⁺

2 P _i

2 ADP

1,3-Bisphospho-�glycerate

3-Phospho-�glycerate

2-Phospho-�glycerate

Phosphoenol-�pyruvate (PEP)

2

2

2

2 H₂O

Phospho-�glycerokinase

Phospho-�glyceromutase

Enolase

Triose�phosphate�dehydrogenase

Figure 9.9-9

Glycolysis: Energy Payoff Phase

2 ATP

2 ATP

2 NADH

2 NAD⁺

+ 2 H⁺

2 P _i

2 ADP

1,3-Bisphospho-�glycerate

3-Phospho-�glycerate

2-Phospho-�glycerate

Phosphoenol-�pyruvate (PEP)

Pyruvate

2 ADP

2

2

2

2 H₂O

Phospho-�glycerokinase

Phospho-�glyceromutase

Enolase

Pyruvate�kinase

Triose�phosphate�dehydrogenase

Figure 9.9a

Glycolysis: Energy Investment Phase

ATP

Glucose

Glucose 6-phosphate

ADP

Hexokinase

Fructose 6-phosphate

Phosphogluco-�isomerase

Figure 9.9b

Glycolysis: Energy Investment Phase

ATP

Fructose 6-phosphate

ADP

Fructose 1,6-bisphosphate

Phospho-�fructokinase

Aldolase

Dihydroxyacetone�phosphate

Glyceraldehyde�3-phosphate

To�step 6

Isomerase

Figure 9.9c

Glycolysis: Energy Payoff Phase

2 NADH

2 ATP

2 ADP

2

2

2 NAD⁺

+ 2 H⁺

2 P _i

3-Phospho-�glycerate

1,3-Bisphospho-�glycerate

Triose�phosphate�dehydrogenase

Phospho-�glycerokinase

Figure 9.9d

Glycolysis: Energy Payoff Phase

2 ATP

2 ADP

2

2

2

2

2 H₂O

Pyruvate

Phosphoenol-�pyruvate (PEP)

2-Phospho-�glycerate

3-Phospho-�glycerate

Phospho-�glyceromutase

Enolase

Pyruvate�kinase

Concept 9.3: After pyruvate is oxidized, the citric acid cycle completes the energy-yielding oxidation of organic molecules

• In the presence of O₂, pyruvate enters the mitochondrion (in eukaryotic cells) where the oxidation of glucose is completed

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

Figure 9.10

Pyruvate

Transport protein

CYTOSOL

MITOCHONDRION

CO₂

Coenzyme A

NAD⁺

+ H⁺

NADH

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

Figure 9.11

Pyruvate

NAD⁺

NADH

+ H⁺

Acetyl CoA

CO₂

CoA

CoA

CoA

2 CO₂

ADP + P _i

FADH₂

FAD

ATP

3 NADH

3 NAD⁺

Citric�acid�cycle

+ 3 H⁺

• 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

Figure 9.12-1

Acetyl CoA

Citrate

Citric�acid�cycle

CoA-SH

Oxaloacetate

Figure 9.12-2

Acetyl CoA

Citrate

Isocitrate

Citric�acid�cycle

H₂O

CoA-SH

Oxaloacetate

Figure 9.12-3

Acetyl CoA

Citrate

Isocitrate

α-Ketoglutarate

Citric�acid�cycle

NADH

+ H⁺

NAD⁺

H₂O

CoA-SH

CO₂

Oxaloacetate

Figure 9.12-4

Acetyl CoA

Citrate

Isocitrate

α-Ketoglutarate

Succinyl�CoA

Citric�acid�cycle

NADH

NADH

+ H⁺

+ H⁺

NAD⁺

NAD⁺

H₂O

CoA-SH

CO₂

CoA-SH

CO₂

Oxaloacetate

Figure 9.12-5

Acetyl CoA

Citrate

Isocitrate

α-Ketoglutarate

Succinyl�CoA

Succinate

Citric�acid�cycle

NADH

NADH

ATP

+ H⁺

+ H⁺

NAD⁺

NAD⁺

H₂O

ADP

GTP

GDP

P _i

CoA-SH

CO₂

CoA-SH

CoA-SH

CO₂

Oxaloacetate

Figure 9.12-6

Acetyl CoA

Citrate

Isocitrate

α-Ketoglutarate

Succinyl�CoA

Succinate

Fumarate

Citric�acid�cycle

NADH

NADH

FADH₂

ATP

+ H⁺

+ H⁺

NAD⁺

NAD⁺

H₂O

ADP

GTP

GDP

P _i

FAD

CoA-SH

CO₂

CoA-SH

CoA-SH

CO₂

Oxaloacetate

Figure 9.12-7

Acetyl CoA

Citrate

Isocitrate

α-Ketoglutarate

Succinyl�CoA

Succinate

Fumarate

Malate

Citric�acid�cycle

NADH

NADH

FADH₂

ATP

+ H⁺

+ H⁺

NAD⁺

NAD⁺

H₂O

H₂O

ADP

GTP

GDP

P _i

FAD

CoA-SH

CO₂

CoA-SH

CoA-SH

CO₂

Oxaloacetate

Figure 9.12-8

NADH

Acetyl CoA

Citrate

Isocitrate

α-Ketoglutarate

Succinyl�CoA

Succinate

Fumarate

Malate

Citric�acid�cycle

NAD⁺

NADH

NADH

FADH₂

ATP

+ H⁺

+ H⁺

+ H⁺

NAD⁺

NAD⁺

H₂O

H₂O

ADP

GTP

GDP

P _i

FAD

CoA-SH

CO₂

CoA-SH

CoA-SH

CO₂

Oxaloacetate

Figure 9.12a

Acetyl CoA

Oxaloacetate

Citrate

Isocitrate

H₂O

CoA-SH

Figure 9.12b

Isocitrate

α-Ketoglutarate

Succinyl�CoA

NADH

NADH

NAD⁺

NAD⁺

+ H⁺

CoA-SH

CO₂

CO₂

+ H⁺

Figure 9.12c

Fumarate

FADH₂

CoA-SH

Succinate

Succinyl�CoA

FAD

ADP

GTP

GDP

P _i

ATP

Figure 9.12d

Oxaloacetate

Malate

Fumarate

H₂O

NADH

NAD⁺

+ H⁺

Concept 9.4: During oxidative phosphorylation, chemiosmosis couples electron transport to ATP synthesis

• Following glycolysis and the citric acid cycle, NADH and FADH₂ account for most of the energy extracted from food
• These two electron carriers donate electrons to the electron transport chain, which powers ATP synthesis via oxidative phosphorylation

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 9.13

NADH

FADH₂

2 H⁺ + ¹/₂ O₂

2 e⁻

2 e⁻

2 e⁻

H₂O

NAD⁺

Multiprotein�complexes

(originally from � NADH or FADH₂)

I

II

III

IV

50

40

30

20

10

0

Free energy (G) relative to O₂ (kcal/mol)

FMN

Fe∙S

Fe∙S

FAD

Q

Cyt b

Cyt c₁

Cyt c

Cyt a

Cyt a₃

Fe∙S

• 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 proton, 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

Figure 9.14

INTERMEMBRANE SPACE

Rotor

Stator

H⁺

Internal�rod

Catalytic�knob

ADP

+

P _i

ATP

MITOCHONDRIAL MATRIX

Figure 9.15

Protein�complex�of electron�carriers

(carrying electrons�from food)

Electron transport chain

Oxidative phosphorylation

Chemiosmosis

ATP�synth-�ase

I

II

III

IV

Q

Cyt c

FAD

FADH₂

NADH

ADP + P _i

NAD⁺

H⁺

2 H⁺ + ¹/₂O₂

H⁺

H⁺

H⁺

H⁺

H₂O

ATP

• 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

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

Figure 9.16

Electron shuttles�span membrane

MITOCHONDRION

2 NADH

2 NADH

2 NADH

6 NADH

2 FADH₂

2 FADH₂

or

+ 2 ATP

+ 2 ATP

+ about 26 or 28 ATP

Glycolysis

Glucose

2 Pyruvate

Pyruvate oxidation

2 Acetyl CoA

Citric�acid�cycle

Oxidative�phosphorylation:�electron transport�and�chemiosmosis

CYTOSOL

Maximum per glucose:

About�30 or 32 ATP

Concept 9.5: Fermentation and anaerobic �respiration enable cells to produce ATP without the use of oxygen

• Most cellular respiration requires O₂ to produce ATP
• Without O₂, the electron transport chain will cease to operate
• In that case, glycolysis couples with 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, with the first releasing CO₂
• Alcohol fermentation by yeast is used in brewing, winemaking, and baking

​

Animation: Fermentation Overview Right-click slide / select “Play”

Figure 9.17

2 ADP

2 ATP

Glucose

Glycolysis

2 Pyruvate

2 CO₂

2

+

2 NADH

2 Ethanol

2 Acetaldehyde

(a) Alcohol fermentation

(b) Lactic acid fermentation

2 Lactate

2 Pyruvate

2 NADH

Glucose

Glycolysis

2 ATP

2 ADP

+

2

P

_i

NAD

2 H⁺

+

2

P

_i

2

NAD

⁺

⁺

+

2 H⁺

Figure 9.17a

2 ADP + 2 P _i

2 ATP

Glucose

Glycolysis

2 Pyruvate

2 CO₂

2 NAD

+

2 NADH

2 Ethanol

2 Acetaldehyde

(a) Alcohol fermentation

⁺

2 H

⁺

• In lactic acid fermentation, pyruvate is reduced to 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

Figure 9.17b

(b) Lactic acid fermentation

2 Lactate

2 Pyruvate

2 NADH

Glucose

Glycolysis

2 ADP + 2 P _i

2 ATP

2 NAD

+

⁺

2 H

⁺

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 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 9.18

Glucose

CYTOSOL

Glycolysis

Pyruvate

No O₂ present:�Fermentation

O₂ present:� Aerobic cellular� respiration

Ethanol,�lactate, or�other products

Acetyl CoA

MITOCHONDRION

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

Concept 9.6: Glycolysis and the citric acid cycle connect to many other metabolic pathways

• Gycolysis and the citric acid cycle are major intersections to various catabolic and anabolic pathways

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

​

• 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

Figure 9.19

Carbohydrates

Proteins

Fatty�acids

Amino�acids

Sugars

Fats

Glycerol

Glycolysis

Glucose

Glyceraldehyde 3- P

NH₃

Pyruvate

Acetyl CoA

Citric�acid�cycle

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

Regulation of Cellular Respiration via Feedback Mechanisms

• Feedback inhibition is the most common mechanism for 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

Figure 9.20

Phosphofructokinase

Glucose

Glycolysis

AMP

Stimulates

−

−

+

Fructose 6-phosphate

Fructose 1,6-bisphosphate

Pyruvate

Inhibits

Inhibits

ATP

Citrate

Citric�acid�cycle

Oxidative�phosphorylation

Acetyl CoA

Figure 9.UN06

Inputs

Outputs

Glucose

Glycolysis

2 Pyruvate + 2

ATP

+ 2 NADH

Figure 9.UN07

Inputs

Outputs

2 Pyruvate

2 Acetyl CoA

2 Oxaloacetate

Citric�acid�cycle

2

2

6

8

ATP

NADH

FADH₂

CO₂

Figure 9.UN08

Protein complex�of electron�carriers

(carrying electrons from food)

INTERMEMBRANE�SPACE

MITOCHONDRIAL MATRIX

H⁺

H⁺

H⁺

2 H⁺ + ¹/₂ O₂

H₂O

NAD⁺

FADH₂

FAD

Q

NADH

I

II

III

IV

Cyt c

Figure 9.UN09

INTER-�MEMBRANE�SPACE

H⁺

ADP + P _i

MITO-�CHONDRIAL�MATRIX

ATP�synthase

H⁺

ATP

Figure 9.UN10

Time

pH difference�across membrane

Figure 9.UN11

ATP

ADP

​

NADH

​

NAD+

FAHD₂

FAD+