introduction in eukaryotes, cellular respiration –harvests energy from food, –yields large...

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.

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Figure 6.0_1Chapter 6: Big Ideas

Cellular Respiration:Aerobic Harvesting

of Energy

Stages of CellularRespiration

Fermentation: AnaerobicHarvesting of Energy

Connections BetweenMetabolic 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

Photosynthesisin chloroplasts

Cellular respirationin mitochondria

(for cellularwork)

Heat energy

GlucoseCO2

H2O O2

ATP

Figure 6.2

Breathing

Lungs

BloodstreamCO2 O2

O2 CO2

Muscle cells carrying out

Cellular Respiration

Glucose O2 CO2 H2O ATP

Figure 6.3

Glucose Oxygen WaterCarbondioxide

C6H12O6 O2 H2O ATP6 6 6

Heat

CO2

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.

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Figure 6.5A

Glucose Heat

C6H12O6 O2 CO2 H2O ATP6 6 6

Loss of hydrogen atoms(becomes oxidized)

Gain of hydrogen atoms(becomes reduced)

Figure 6.5C

Controlledrelease ofenergy forsynthesisof ATP

NADH

NAD

H

H O2

H2O

2

2

2

ATP

Electron transport chain

21

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 three-carbon 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.

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Figure 6.6_1

NADH

NADH FADH2

ATP ATPATP

CYTOPLASM

Glycolysis

Electronscarried by NADH

Glucose Pyruvate PyruvateOxidation

Citric AcidCycle

OxidativePhosphorylation

(electron transportand chemiosmosis)

Mitochondrion

Substrate-levelphosphorylation

Substrate-levelphosphorylation

Oxidativephosphorylation

Figure 6.7Ca_s1Glucose

Glucose 6-phosphate

Fructose 6-phosphate

Fructose 1,6-bisphosphate

ENERGYINVESTMENT

PHASE

P P

P

P

ADP

ADP

ATP

ATP

StepSteps – A fuelmolecule is energized,using ATP.

3

3

2

1

1

Figure 6.7Ca_s2Glucose

Glucose 6-phosphate

Fructose 6-phosphate

Fructose 1,6-bisphosphate

Glyceraldehyde3-phosphate (G3P)

ENERGYINVESTMENT

PHASE

PP

P P

P

P

ADP

ADP

ATP

ATP

StepSteps – A fuelmolecule is energized,using ATP.

Step A six-carbonintermediate splitsinto two three-carbonintermediates.

4

4

3

3

2

1

1

Figure 6.7Cb_s1

5 5 5Step A redox reactiongenerates NADH.

ENERGYPAYOFFPHASE

1,3-Bisphospho-glycerate

NADH NADH

NADNAD

H H

P P

P

P P

P

P P

Figure 6.7Cb_s2

66 6

5 5 5

9

9 9

8 8

7 7

Step A redox reactiongenerates NADH.

Steps – ATP and pyruvateare produced.

ENERGYPAYOFFPHASE

1,3-Bisphospho-glycerate

3-Phospho-glycerate

2-Phospho-glycerate

Phosphoenol-pyruvate (PEP)

Pyruvate

NADH NADH

NADNAD

H H

ADP ADP

ADP ADP

ATP ATP

ATP ATP

H2O H2O

P P

P

P P

P

P

P

P

P P

P

P

P

Figure 6.8

Pyruvate

Coenzyme A

Acetyl coenzyme A

NAD NADH H

CoA

CO2

3

2

1

Figure 6.9AAcetyl CoA

Citric Acid Cycle

CoA

CoA

CO22

3

3

NAD

3 H

NADH

ADPATP P

FAD

FADH2

Figure 6.9B_s3

NADH

NADH

NAD

NAD

NADNADH

H

H

H

CO2

CO2

ATP

ADP P

FAD

FADH2

CoA

CoA

321 4 5

34

5

1

2

Acetyl CoA

Oxaloacetate

Citric Acid Cycle

2 carbons enter cycle

Citrate

leaves cycle

Alpha-ketoglutarate

leaves cycle

Succinate

Malate

StepAcetyl CoA stokesthe furnace.

Steps –NADH, ATP, and CO2

are generated during redox reactions.

Steps –Further redox reactions generateFADH2 and more NADH.

Figure 6.10_1

H

H

H

H

H

H

H

H

H

H

H

Oxidative Phosphorylation

Electron Transport Chain Chemiosmosis

I

II

IIIIV

NADH NAD 2 H

FADH2FAD

O2 H2O

ADP P ATP

21

Electronflow

Proteincomplexof electroncarriers

Mobileelectroncarriers

ATPsynthase

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.

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Figure 6.12

NADH

FADH2

NADH FADH2NADH

orNADH

MitochondrionCYTOPLASM

Electron shuttlesacross membrane

Glycolysis

Glucose2

Pyruvate

PyruvateOxidation2 Acetyl

CoA

Citric AcidCycle

OxidativePhosphorylation

(electron transportand chemiosmosis)

Maximumper glucose:

by substrate-levelphosphorylation

by substrate-levelphosphorylation

by oxidativephosphorylation

2

2

2

2

6 2

ATP 2 about

28 ATP AboutATP32

ATP 2

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Animation: Fermentation OverviewRight click on animation / Click play

Figure 6.13A

2 NAD

2 NADH

2 NAD

2 NADH

2 Lactate

2 Pyruvate

Glucose

2 ADP

2 ATP

2 P

Gly

coly

sis

Figure 6.13B

2 NAD

2 NADH

2 NAD

2 NADH

2 Ethanol

2 Pyruvate

Glucose

2 ADP

2 ATP

2 P

Gly

coly

sis

2 CO2

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.

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Figure 6.15

Food, such aspeanuts

Sugars Glycerol Fatty acids Amino acids

Aminogroups

OxidativePhosphorylation

CitricAcidCycle

PyruvateOxidation

Acetyl CoA

ATP

Glucose G3P PyruvateGlycolysis

Carbohydrates Fats Proteins

Figure 6.16

CarbohydratesFatsProteins

Cells, tissues, organisms

Amino acids Fatty acids Glycerol Sugars

Aminogroups

CitricAcidCycle

PyruvateOxidation

Acetyl CoA

ATP neededto drivebiosynthesis

ATP

Glucose SynthesisPyruvate G3P Glucose

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.

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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.

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Figure 6.UN01

Substrate-levelphosphorylation

Substrate-levelphosphorylation

OxidativephosphorylationATP ATP

ATP

NADH

NADH FADH2

Mitochondrion

GlycolysisPyruvateOxidation

CitricAcidCycle

OxidativePhosphorylation

(electron transportand chemiosmosis)

Electronscarried by NADH

Glucose Pyruvate

CYTOPLASM

Figure 6.UN02

cellular work

chemiosmosis

H gradient

glucose andorganic fuels

Cellularrespiration

generates has three stages oxidizes

uses

producesome

producesmany

to pullelectrons down

H diffusethrough

ATP synthase

pumps H to createuses

usesby a process called

energy for

(a)

(b)

(c)

(d)

(e)

(f)

(g)

to