Cellular Respiration Harvesting Chemical Energy

Page
7

FAD

FADH2

Fumarate

Citric

acid

cycle

H2O

Malate

1

2

5

6

7

i

CO2

+ H+

3

4

Slide 51

Fig. 9-12-8

Acetyl CoA

CoA—SH

Citrate

H2O

Isocitrate

NAD+

NADH

+ H+

CO2

-Keto-

glutarate

CoA—SH

CO2

NAD+

NADH

+ H+

Succinyl

CoA

CoA—SH

P

i

GTP

GDP

ADP

ATP

Succinate

FAD

FADH2

Fumarate

Citric

acid

cycle

H2O

Malate

Oxaloacetate

NADH

+H+

NAD+

1

2

3

4

5

6

7

8

Slide 52

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

Slide 53

The Pathway of Electron Transport

The electron transport chain is in the 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

Slide 54

Fig. 9-13

NADH

NAD+

2

FADH2

2

FAD

Multiprotein

complexes

FAD

Fe•S

FMN

Fe•S

Q

Fe•S



Cyt b





Cyt c1

Cyt c

Cyt a

Cyt a3

IV

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

50

40

30

20

10

2

(from NADH

or FADH2)

0

2 H+ + 1/2

O2

H2O

e–

e–

e–

Slide 55

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

The chain’s function is to break the large free-energy drop from food to O2 into smaller steps that release energy in manageable amounts

Slide 56

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 channels in ATP synthase