10 ge lecture presentation

BIOLOGYA Global Approach

Campbell • Reece • Urry • Cain • Wasserman • Minorsky • Jackson

© 2015 Pearson Education Ltd

TENTH EDITION

Global Edition

Lecture Presentation by Nicole Tunbridge andKathleen Fitzpatrick

10

Cell Respiration


Life Is Work

a) Living cells require energy from outside sources

b) Some animals, such as the giraffe, obtain energy by eating plants, and some animals feed on other organisms that eat plants


Figure 10.1


a) Energy flows into an ecosystem as sunlight and leaves as heat

b) Photosynthesis generates O2 and organic molecules, which are used in cellular respiration

c) Cells use chemical energy stored in organic molecules to generate ATP, which powers work


Figure 10.2

Lightenergy

Organicmolecules O2CO2 H2O+

Photosynthesisin chloroplasts

Cellular respirationin mitochondria

ECOSYSTEM

ATP powersmost cellular workATP

Heatenergy

+


BioFlix: The Carbon Cycle


Concept 10.1: Catabolic pathways yield energy by oxidizing organic fuels

a) Catabolic pathways release stored energy by breaking down complex molecules

b) Electron transfer plays a major role in these pathways

c) These processes are central to cellular respiration


Catabolic Pathways and Production of ATP

a) The breakdown of organic molecules is exergonic

b)Fermentation is a partial degradation of sugars that occurs without O2

c) Aerobic respiration consumes organic molecules and O2 and yields ATP

d) Anaerobic respiration is similar to aerobic respiration but consumes compounds otherthan O2


a) Cellular respiration includes both aerobic and anaerobic respiration but is often used to refer to aerobic respiration

b) 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

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

b) This released energy is ultimately used to synthesize ATP


The Principle of Redox

a) Chemical reactions that transfer electrons between reactants are called oxidation-reduction reactions, or redox reactions

b) In oxidation, a substance loses electrons,or is oxidized

c) In reduction, a substance gains electrons, or is reduced (the amount of positive charge is reduced)


Stepwise Energy Harvest via NAD+ and the Electron Transport Chain

a) In cellular respiration, glucose and other organic molecules are broken down in a series of steps

b) Electrons from organic compounds are usually first transferred to NAD+, a coenzyme

c) As an electron acceptor, NAD+ functions as an oxidizing agent during cellular respiration

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


Figure 10.4

NAD+

2 e− + 2 H+

2[H](from food)

Nicotinamide(oxidized form)

Reduction of NAD+

2 e− + H+

NADH

Nicotinamide(reduced form)

Oxidation of NADHH+

H+

Dehydrogenase


Figure 10.UN04

Dehydrogenase


a) NADH passes the electrons to the electron transport chain

b) Unlike an uncontrolled reaction, the electron transport chain passes electrons in a series of steps instead of one explosive reaction

c) O2 pulls electrons down the chain in an energy-yielding tumble

d) The energy yielded is used to regenerate ATP


Figure 10.5

H2 +½ O2 2 H + ½ O2

2 H+

2 e−

2 e−2 H+ +

H2O

½ O2

Controlledrelease of

energy

Electron transport

chain

ATP

ATP

ATPExplosive

release

Cellular respirationUncontrolled reaction(a) (b)

Free

ene

rgy,

G

Free

ene

rgy,

G

H2O


The Stages of Cellular Respiration: A Preview

a) Harvesting of energy from glucose has three stages

a)Glycolysis (breaks down glucose into two molecules of pyruvate)

b)The citric acid cycle (completes the breakdown of glucose)

c)Oxidative phosphorylation (accounts for most of the ATP synthesis)


Figure 10.UN05

1.2.

3.

GLYCOLYSIS (color-coded blue throughout the chapter)PYRUVATE OXIDATION and the CITRIC ACID CYCLE(color-coded orange)

OXIDATIVE PHOSPHORYLATION: Electron transport andchemiosmosis (color-coded purple)


Figure 10.6-1

Electronsvia NADH

ATP

CYTOSOL MITOCHONDRION

Substrate-level

GLYCOLYSIS

Glucose Pyruvate


Figure 10.6-2

Electronsvia NADH

Electronsvia NADHand FADH2

ATP ATP


Substrate-level Substrate-level

GLYCOLYSIS PYRUVATEOXIDATION CITRIC

ACIDCYCLEAcetyl CoAGlucose Pyruvate


Figure 10.6-3

Electronsvia NADH

Electronsvia NADHand FADH2

ATP ATP ATP


Substrate-level Substrate-level Oxidative

GLYCOLYSIS PYRUVATEOXIDATION CITRIC

ACIDCYCLE

OXIDATIVEPHOSPHORYLATION

(Electron transportand chemiosmosis)

Acetyl CoAGlucose Pyruvate


BioFlix: Cellular Respiration


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


a) Oxidative phosphorylation accounts for almost 90% of the ATP generated by cellular respiration

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

c) For each molecule of glucose degraded to CO2 and water by respiration, the cell makes up to 32 molecules of ATP


Figure 10.7

Enzyme Enzyme

Substrate

Product

ATP

ADP

P


Concept 10.2: Glycolysis harvests chemical energy by oxidizing glucose to pyruvate

a) Glycolysis (“sugar splitting”) breaks down glucose into two molecules of pyruvate

b) Glycolysis occurs in the cytoplasm and has two major phases

a)Energy investment phase

b)Energy payoff phase

c) Glycolysis occurs whether or not O2 is present


Figure 10.UN06

GLYCOLYSIS PYRUVATEOXIDATION

CITRICACID

CYCLE

OXIDATIVEPHOSPHORYL-

ATION

ATP


Figure 10.8

Energy Investment Phase

Glucose

Energy Payoff Phase

Net

2 ATP used 2 ADP + 2 P

4 ADP + 4 P 4 ATP formed

NAD+ 4 e−2 + + 4 H+ 2 H+2 NADH

Pyruvate2

2

2

2

2

2

2

2 H+H+

4

4

Glucose Pyruvate

ATPATP usedATP formedH2O

NADH

−

2 NAD+

+

+

+

++ +

2 H2O

4e−


Concept 10.3: After pyruvate is oxidized, the citric acid cycle completes the energy-yielding oxidation of organic molecules

a) 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

a) 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

b) This step is carried out by a multienzyme complex that catalyses three reactions


Figure 10.UN07


CITRICACID

CYCLE


ATION


Figure 10.10

CYTOSOL

Pyruvate

Transport protein

MITOCHONDRION

Acetyl CoANAD+ H+NADH +

CO2Coenzyme A

1

2

3


The Citric Acid Cycle

a) The citric acid cycle, also called the Krebs cycle, completes the break down of pyruvate to CO2

b) The cycle oxidizes organic fuel derived from pyruvate, generating 1 ATP, 3 NADH, and 1 FADH2 per turn


Figure 10.11

PYRUVATE OXIDATIONPyruvate (from glycolysis,2 molecules per glucose)

NADH

NAD+CO2

CoA

CoA+ H+

CoA

CoA

CO2

CITRICACID

CYCLE

FADH2

FAD

ATP

ADP + P i

NAD+

+ 3 H+

NADH3

3

2

Acetyl CoA


Figure 10.11a

PYRUVATE OXIDATIONPyruvate (from glycolysis,2 molecules per glucose)

NADH

NAD+CO2

CoA

CoA+ H+ Acetyl CoA


Figure 10.11b

CoA

CoA

CO2

CITRICACID

CYCLEFADH2

FAD

ATPADP + P i

NAD+

+ 3 H+

NADH3

3

2

Acetyl CoA


a) The citric acid cycle has eight steps, each catalyzed by a specific enzyme

b) The acetyl group of acetyl CoA joins the cycle by combining with oxaloacetate, forming citrate

c) The next seven steps decompose the citrate back to oxaloacetate, making the process a cycle

d) The NADH and FADH2 produced by the cycle relay electrons extracted from food to the electron transport chain


Figure 10.UN08


CITRICACID

CYCLE


ATION

ATP


Figure 10.12-1

Acetyl CoA

Oxaloacetate

CoA-SH

Citrate

CITRICACID

CYCLE

1


Figure 10.12-2

Acetyl CoA

H2O

Oxaloacetate

CoA-SH

Citrate

CITRICACID

CYCLE

Isocitrate

1

2


Figure 10.12-3

Acetyl CoA

H2O

+ H+

Oxaloacetate

CoA-SH

Citrate

-Ketoglutarate

NAD+

CO2

NADHCITRICACID

CYCLE

Isocitrate

1

2

3


Figure 10.12-4

Acetyl CoA

H2O

+ H+

Oxaloacetate

CoA-SH

Citrate

-KetoglutarateCoA-SH

NAD+

CO2

NADH

CO2NAD+

NADH+ H+

SuccinylCoA

CITRICACID

CYCLE

Isocitrate

1

2

4

3


Figure 10.12-5

Acetyl CoA

H2O

+ H+

Oxaloacetate

CoA-SH

Citrate


NAD+

CO2

NADH

CO2NAD+

NADH+ H+

SuccinylCoA

ATP

ADP

GTP GDPSuccinate

CITRICACID

CYCLE

Pi

Isocitrate

1

2

5

4

3

CoA-SH


Figure 10.12-6

Acetyl CoA

H2O

+ H+

Oxaloacetate

CoA-SH

Citrate


NAD+

CO2

NADH

CO2NAD+

NADH+ H+

SuccinylCoA

ATP

ADP

GTP GDPSuccinateFAD

FADH2

Fumarate

CITRICACID

CYCLE

Pi

Isocitrate

1

2

5

6 4

3

CoA-SH


Figure 10.12-7

Acetyl CoA

H2O

+ H+

Oxaloacetate

CoA-SH

Citrate


NAD+

CO2

NADH

CO2NAD+

NADH+ H+

SuccinylCoA

ATP

ADP

GTP GDPSuccinateFAD

FADH2

Fumarate

H2O

Malate

CITRICACID

CYCLE

Pi

Isocitrate

1

2

5

6 4

37

CoA-SH


Figure 10.12-8

Acetyl CoA

H2O

+ H+

Oxaloacetate

CoA-SH

Citrate


NAD+

CO2

NADH

CO2NAD+

NADH+ H+

SuccinylCoA

ATP

ADP

GTP GDPSuccinateFAD

FADH2

Fumarate

H2O

Malate

CITRICACID

CYCLE

+ H+

NAD+

Pi

NADH

Isocitrate

1

2

5

6 4

37

8

CoA-SH


Concept 10.4: During oxidative phosphorylation, chemiosmosis couples electron transport to ATP synthesis

a) Following glycolysis and the citric acid cycle, NADH and FADH2 account for most of the energy extracted from food

b) These two electron carriers donate electrons to the electron transport chain, which powers ATP synthesis via oxidative phosphorylation


The Pathway of Electron Transport

a) The electron transport chain is in the inner membrane (cristae) of the mitochondrion

b) Most of the chain’s components are proteins,which exist in multiprotein complexes

c) The carriers alternate reduced and oxidized states as they accept and donate electrons

d) Electrons drop in free energy as they go down the chain and are finally passed to O2, forming H2O


Figure 10.UN09

GLYCOLYSISCITRICACID

CYCLE

PYRUVATEOXIDATION

ATP


ATION


Figure 10.13

NADH

e−2 NAD+

FADH2

FAD2 e−

FMNFe•S

Q

Fe•S

Cyt bFe•S

Cyt c1

Cyt cCyt a

Cyt a3

e−2(originally from

NADH or FADH2)

2 H+ + ½ O2

H2O

MultiproteincomplexesI

II

III

IV

50

40

30

20

10

0

Free

ene

rgy

(G) r

elat

ive

to O

2 (kc

al/m

ol)


Figure 10.13a

50

40

30

20

10

Free

ene

rgy

(G) r

elat

ive

to O

2 (kc

al/m

ol)

NADH

e−2 NAD+

FADH2

Fe•S

e−

FMNFe•S

QCyt b

FADIII

FAD Multiproteincomplexes

III

Fe•SCyt c1

Cyt cCyt a

Cyt a3

IV

2

e−2


Figure 10.13b

30

20

10

Free

ene

rgy

(G) r

elat

ive

to O

2 (kc

al/m

ol)

0

Cyt c1

Cyt cCyt a

Cyt a3

IV

e−2

2 H+ + ½ O2

H2O

(originally fromNADH or FADH2)


a) Electrons are transferred from NADH or FADH2 to the electron transport chain

b) Electrons are passed through a number of proteins including cytochromes (each with an iron atom) to O2

c) The electron transport chain generates no ATP directly

d) 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

a) Electron transfer in the electron transport chain causes proteins to pump H+ from the mitochondrial matrix to the intermembrane space

b) H+ then moves back across the membrane, passing through the protein complex, ATP synthase

c) ATP synthase uses the exergonic flow of H+ to drive phosphorylation of ATP

d) This is an example of chemiosmosis, the use of energy in a H+ gradient to drive cellular work


Figure 10.14

INTERMEMBRANESPACE

RotorH+ Stator

Internal rod

Catalyticknob

ADP+P i

MITOCHONDRIALMATRIX

ATP


Video: ATP Synthase 3-D Structure, Top View


Video: ATP Synthase 3-D Structure, Side View


Figure 10.15

Proteincomplexof electroncarriers

(carryingelectronsfromfood)

ATPsynthase

Electron transport chain Chemiosmosis

Oxidative phosphorylation

2 H+ + ½ O2 H2O

ADP + P i

H+

ATP

H+

H+

H+

H+

Cyt c

QI

II

III

IV

FADFADH2

NADH NAD+

1 2


Figure 10.15a

Proteincomplexof electroncarriers

2 H+ + ½ O2 H2O

H+

NAD+

1

H+

H+

NADH

FADH2

Cyt cCyt c

IV

III

II

I

FAD

(carryingelectronsfromfood) Electron transport chain

Q


Figure 10.15b

H+

2

H+

ADP + P i ATP

Chemiosmosis

ATPsynthase


a) The energy stored in a H+ gradient across a membrane couples the redox reactions of the electron transport chain to ATP synthesis

b) 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

a) During cellular respiration, most energy flows in this sequence:

glucose → NADH → electron transport chain → proton-motive force → ATP

b) About 34% of the energy in a glucose molecule is transferred to ATP during cellular respiration, making about 32 ATP

c) There are several reasons why the number of ATP is not known exactly


Figure 10.16

Electron shuttlesspan membrane

CYTOSOL 2 NADHor

2 FADH2

2 NADH 2 FADH26 NADH

MITOCHONDRION

OXIDATIVEPHOSPHORYLATION(Electron transportand chemiosmosis)

CITRICACID

CYCLE

PYRUVATEOXIDATION

2 Acetyl CoA

GLYCOLYSIS

Glucose 2Pyruvate

+ 2 ATP + 2 ATP

Maximum per glucose: About30 or 32 ATP

+ about 26 or 28 ATP

2 NADH


Concept 10.5: Fermentation and anaerobic respiration enable cells to produce ATP without the use of oxygen

a) Most cellular respiration requires O2 to produce ATP

b) Without O2, the electron transport chain will cease to operate

c) In that case, glycolysis couples with anaerobic respiration or fermentation to produce ATP


a) Anaerobic respiration uses an electron transport chain with a final electron acceptor other than O2, for example sulfate

b) Fermentation uses substrate-level phosphorylation instead of an electron transport chain to generate ATP


Types of Fermentation

a) Fermentation consists of glycolysis plus reactions that regenerate NAD+, which can be reused by glycolysis

b) Two common types are alcohol fermentation and lactic acid fermentation


a) In alcohol fermentation, pyruvate is converted to ethanol in two steps

a)The first step releases CO2

b)The second step produces ethanol

b) Alcohol fermentation by yeast is used in brewing, winemaking, and baking


Figure 10.17

2 ADP + 2 P i 2 ATP

Glucose

2 NAD+ NADH2+ 2 H+

2 Pyruvate

CO22

2 Ethanol

(a) Alcohol fermentation

2 Acetaldehyde 2 LactateLactic acid fermentation

2 ADP + 2 P i 2 ATP

GLYCOLYSIS

NAD+

+ 2 H+

NADH22

2 Pyruvate

(b)

GLYCOLYSIS Glucose


Figure 10.17a

2 ADP + 2 P i

NAD+

+ 2 H+

GLYCOLYSISGlucose

2 ATP

22

2 Ethanol 2 Acetaldehyde

2 Pyruvate

(a) Alcohol fermentation

2 CO2NADH


Figure 10.17b

2 ADP + 2 P i

NAD+

+ 2 H+

GLYCOLYSISGlucose

2 ATP

22

Lactate(b) Lactic acid fermentation

NADH

2 Pyruvate

2


Animation: Fermentation Overview


a) In lactic acid fermentation, pyruvate is reduced by NADH, forming lactate as an end product, with no release of CO2

b) Lactic acid fermentation by some fungi and bacteria is used to make cheese and yogurt

c) Human muscle cells use lactic acid fermentation to generate ATP when O2 is scarce


Comparing Fermentation with Anaerobic and Aerobic Respiration

a) All use glycolysis (net ATP = 2) to oxidize glucose and harvest chemical energy of food

b) In all three, NAD+ is the oxidizing agent that accepts electrons during glycolysis


a) The processes have different mechanisms for oxidizing NADH:

a)In fermentation, an organic molecule (such as pyruvate or acetaldehyde) acts as a final electron acceptor

b)In cellular respiration electrons are transferred to the electron transport chain

b) Cellular respiration produces 32 ATP per glucose molecule; fermentation produces 2 ATP per glucose molecule


Figure 10.18Glucose

GlycolysisCYTOSOL

Pyruvate

No O2 present:Fermentation

O2 present: Aerobic cellular respiration

Ethanol,lactate, or

other products

MITOCHONDRIONAcetyl CoA

CITRICACID

CYCLE


The Evolutionary Significance of Glycolysis

a) Ancient prokaryotes are thought to have used glycolysis long before there was oxygen in the atmosphere

b) 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

c) Glycolysis is a very ancient process


Concept 10.6: Glycolysis and the citric acid cycle connect to many other metabolic pathways

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


The Versatility of Catabolism

a) Catabolic pathways funnel electrons from many kinds of organic molecules into cellular respiration

b) Glycolysis accepts a wide range of carbohydrates

c) Proteins must be digested to amino acids; amino groups can feed glycolysis or the citric acid cycle


a) Fats are digested to glycerol (used in glycolysis) and fatty acids (used in generating acetyl CoA)

b) Fatty acids are broken down by beta oxidation and yield acetyl CoA

c) An oxidized gram of fat produces more than twice as much ATP as an oxidized gram of carbohydrate


Figure 10.19-1

Proteins Carbohydrates Fats

Aminoacids

Sugars Glycerol Fattyacids


Figure 10.19-2


Aminoacids


GLYCOLYSISGlucose

Glyceraldehyde 3- P

PyruvateNH3


Figure 10.19-3


Aminoacids


GLYCOLYSISGlucose

Glyceraldehyde 3- P

Pyruvate

Acetyl CoA

NH3


Figure 10.19-4


Aminoacids


GLYCOLYSISGlucose

Glyceraldehyde 3- P

Pyruvate

Acetyl CoA

CITRICACID

CYCLE

NH3


Figure 10.19-5


Aminoacids


GLYCOLYSISGlucose

Glyceraldehyde 3- P

Pyruvate

Acetyl CoA

CITRICACID

CYCLE

OXIDATIVEPHOSPHORYLATION

NH3


Biosynthesis (Anabolic Pathways)

a) The body uses small molecules to build other substances

b) These small molecules may come directly from food, from glycolysis, or from the citric acid cycle


Regulation of Cellular Respiration via Feedback Mechanisms

a) Feedback inhibition is the most common mechanism for metabolic control

b) If ATP concentration begins to drop, respiration speeds up; when there is plenty of ATP, respiration slows down

c) Control of catabolism is based mainly on regulating the activity of enzymes at strategic points in the catabolic pathway


Figure 10.UN17

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