Cellular Respiration Part 4Oxidative PhosphorylationPages 98 to 100

Oxidative Phosphorylation• Location

▫ Cristae of mitochondria

• Final Acceptor of Electrons▫ Oxygen

Fig. 9-13

(from NADHor FADH2)

NADH

NAD+2FADH2

2 FAD Multiproteincomplexes

FAD

Fe•S

FMN

Fe•S

Q

Fe•S

Cyt b

Cyt c1 Cyt

cCyt a Cyt

a3

IV

Fre

e e

nerg

y (G

) re

lati

ve t

o O

2

(kcal /

mol )

50

40

30

20

10

2

0 2 H+ + 1/2 O2

H2O

e–

e–

e–

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

Electrons are passed through a number of proteins 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

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

Intermembrane space becomes positively charged; the matrix because negatively charged – concentration gradient is established = potential energy

Fig. 9-14INTERMEMBRANE SPACE

Rotor

H+

Stator

Internalrod

Catalyticknob

ADP+P AT

Pi

MITOCHONDRIAL MATRIX

As H+ escapes from positively charged intermembrane space through ATP Synthase to the negatively charged matrix, ATP synthase spins using energy released from H+ going down its concentration gradient to phosphorylate ADP making ATP

Chemiosmosis is using energy of a H+ gradient to do cellular work

NADH makes 3 ATP; FADH2 makes 2 ATP

Process NADH FADH2 ATP

Glycolysis 2 0 2

Krebs Cycle 8 2 2

ETC & Chemiosmosis

10 X 3 = 30 2 X 2 = 4 30 + 4 = 34

Debt (entering mitochondria)

2 ATP expended to transport NADH to ETC from cytoplasm

-2

Total 36

ATP Yield from 1 glucose

Certain Poisons Interrupt Events in Cellular Respiration

3 Categories of Poison

•ETC Inhibitors▫Rotenone Blocks ETC at 1st protein complex▫Cyanide and CO2 block ETC at 3rd protein

complex RESULT = no H+gradient no ATP

•ATP synthase Inhibitors▫Oligiomycin ▫Keep H+ from passing through ATP

synthase RESULT = no chemiosmosis

3 Categories of Poison

•Uncouplers ▫Make the membrane of the mitochondria

“leaky” to H+▫Dintrophenol (DNP) unsuccessfully used for

weight loss RESULT – Can’t establish H+ gradeint no

ATP

Benefit of poisons…

•Pesticides•Antibodies•Help to understand the biochemistry of

cellular respiration