Slide 1 

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

PowerPoint® Lecture Presentations for

BiologyEighth Edition

Neil Campbell and Jane Reece

Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp

Chapter 9

Cellular Respiration: Harvesting Chemical Energy

 

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Slide 2  Metabolism

• Thermodynamics says that the flow of chemical energy into a system is equal to:

– the energy used as work

– the energy lost as heat

– the chemical potential energy stored

– true for ecosystems, organisms, tissues, cells

 

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Slide 3 Fig. 9-2

Lightenergy

ECOSYSTEM

Photosynthesisin chloroplasts

CO2 + H2O

Cellular respirationin mitochondria

Organicmolecules+ O2

ATP powers most cellular work

Heatenergy

ATP

 

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Slide 4  Metabolic pathways

• Catabolic pathways release energy (exergonic) by breaking down complex molecules into simpler compounds

• Work pathways couple the energy derived from exergonic reactions to perform an endergonic activity – together the whole is always exergonic

– Anabolic pathways

– Mechanical work

– Transport work

Free energyavailable for work

Heat energylost to the organism

More heat energylost to the organism!

 

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Slide 5  Catabolism in Animals

GLYCOLYSIS

CITRIC ACID CYCLE

OXYDATIVE LACTIC ACIDPHOSPHORYLATION FERMENTATION(electron transport)(chemiosmosis)

high O2

low O2

“CellularRespiration”

or“Aerobic

Metabolism” “AnaerobicMetabolism”

 

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Slide 6  Catabolism for Energy Harvest in Animals

GLUCOSE

PYRUVATE

ACETYL-CoA LACTATE(and CO2)

NADH/FADH2 PYRUVATE(and 2 CO2)

H2O

glycolysis

lactic acid fermentation

citric acid cycle

oxydativephosphorylation

mitocyto

liver conversion

 

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Slide 7  Other Catabolic Pathways

• Fermentation is a partial degradation of sugars that occurs (with/without) O2– Alcohol fermentation –Saccharomyces cerevisiae– Lactic acid fermentation – Lactobacillus acidophilus– Acetic acid fermentation – Escherichia coli

• Anaerobic respiration is similar to aerobic respiration but consumes compounds other than O2

– Sulfate-reducing bacteria and archaea

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  

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Slide 8 

• 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)

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  

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Slide 9  The Principle of Redox

How does the breakdown of glucose yield energy?

• The transfer of electrons during chemical reactions releases energy stored in organic molecules

• Chemical reactions that transfer electrons between reactants are called oxidation-reduction reactions

- or redox reactions

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  

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Slide 10  The Principle of Redox

• In oxidation, a substance loses electrons, or is oxidized

• In reduction, a substance gains electrons, or is reduced.

an oxidized reactant is more (+)

a reduced reactant is less (+)

• The electron donor is called the reducing agent

• The electron receptor is called the oxidizing agent

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  

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Slide 11  Oxidation of Organic Fuel Molecules During Cellular Respiration

• During cellular respiration, the fuel (such as glucose) is ______, and O2 is _______:

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

becomes ________

becomes _______

 

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Slide 12 Electrons are transferred to O2 when glucose bonds are broken and H2O bonds are formed

– Oxygen attracts electrons and electrons lose potential energy when they move to oxygen

C6H12O6 CO26 H2O ATPs

Glucose Oxygen gas Carbon dioxide

6

Water Energy

O2 6+ + +

Can’t see electrons moving, but can see H atoms redistributing

 

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Slide 13  Oxidation of Organic Fuel Molecules During Cellular Respiration

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Dehydrogenase

Electrons travel with a proton (in the form of a H atom)

H atoms are not transferred directly to oxygen, but first to an electron carrier, the coenzyme NAD+

Dehydrogenases remove H atoms from the substrate (glucose)

 

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Slide 14 Fig. 9-4

Dehydrogenase

Reduction of NAD+

Oxidation of NADH

2 e– + 2 H+

2 e– + H+

NAD+ + 2[H]

NADH

+

H+

H+

Nicotinamide(oxidized form)

Nicotinamide(reduced form)

Nicotinamide adenine dinucleotide

Nicotinamide = nitrogenous base (but not part of DNA/RNA)

 

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Slide 15  Oxidation of Organic Fuel Molecules During Cellular Respiration

• If NAD+ is an electron acceptor, is it an oxidizing or reducing agent?

• Each NADH (the ______ form of NAD+) represents stored energy that is tapped to synthesize ATP

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  

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Slide 16  Catabolism in Animals

GLYCOLYSIS

CITRIC ACID CYCLE

OXYDATIVE LACTIC ACIDPHOSPHORYLATION FERMENTATION(electron transport)(chemiosmosis)

high O2

low O2

“CellularRespiration”

or“Aerobic

Metabolism” “AnaerobicMetabolism”

 

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Slide 17 Fig. 9-6-3

Mitochondrion

Substrate-levelphosphorylation

ATP

Cytosol

Glucose Pyruvate

Glycolysis

Electronscarried

via NADH

Substrate-levelphosphorylation

ATP

Electrons carriedvia NADH and

FADH2

Oxidativephosphorylation

ATP

Citricacidcycle

Oxidativephosphorylation:electron transport

andchemiosmosis

Energy Yield from Cellular Respiration

 

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Slide 18 

• The process that generates most of the ATP (almost 90%) is called oxidative phosphorylation because it is powered by redox reactions

• A smaller amount of ATP is formed in glycolysis and the citric acid cycle by substrate-level phosphorylation

BioFlix: Cellular RespirationCopyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Enzyme

ADPP

Substrate

Enzyme

ATP+Product

Energy Yield from Cellular Respiration

 

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Slide 19 Energy Yield from Cellular Respiration

Glucose 2 Pyruvate

• Steps 1 and 3 cost a single ATP

• Step 6 pays out 2 NADH

• Step 7 pays out 2 ATP (phosphoglycerokinse)

• Step 10 pays out 2 ATP (pyruvate kinase)

10 enzymatic steps

glycolysis

 

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Slide 20 Fig. 9-10

CYTOSOL MITOCHONDRION

NAD+ NADH + H+

2

1 3

Pyruvate

Transport protein

CO2Coenzyme A

Acetyl CoA

In the presence of O2, pyruvate enters the mitochondrion.

Before the citric acid cycle can begin, pyruvate must be converted to acetyl CoA – this is the junction between the citric acid cycle and glycolysis

Yield = 2 NADH per glucose

 

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Slide 21 Energy Yield from Cellular Respiration

2 Ac-CoA 4 CO2

• Steps 3, 4, 8 pay out 1 NADH per Ac-CoA

• Step 6 pays out 1 FADH2 per Ac-CoA

• Step 5 pays out 1 ATP per Ac-CoA (SLP)

8 enzymatic steps

Krebs Cycle

 

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Slide 22 Energy Yield from Cellular Respiration

glucose 6 CO2

• Total cost 2 ATP

• Total pay out 6 ATP (SLP)

• Total pay out 10 NADH

• Total pay out 2 FADH2

21 enzymatic steps

glycolysis, Ac-CoA, Krebs

 

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