Cellular Respiration Part IV: Oxidative Phosphorylation

Curriculum Framework

• 2A2 Organisms capture and store free energy for use in biological processes.

g. The electron transport chain captures free energy from electrons in a series of coupled reactions that establish an electrochemical gradient across membranes.

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Figure 9.6-3

Electrons

carried

via NADH

Electrons carried

via NADH and

FADH2

Citric

acid

cycle

Pyruvate

oxidation

Acetyl CoA

Glycolysis

Glucose Pyruvate

Oxidative

phosphorylation:

electron transport

and

chemiosmosis

CYTOSOL MITOCHONDRION

ATP ATP ATP

Substrate-level

phosphorylation

Substrate-level

phosphorylation Oxidative

phosphorylation

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Oxidative Phosphorylation:

Electron Transport and Chemiosmosis

2A2g2. In cellular respiration, electrons delivered by NADH and FADH2 are passed to a series of electron acceptors as they move toward the terminal electron acceptor, oxygen.

Curriculum Framework

t and Chemiosmosis

2A2g3. The passage of electrons is accompanied by the formation of a proton gradient across the inner mitochondrial membrane or the thylakoid membrane of chloroplasts, with the membrane separating a region of high proton concentration from a region of low proton concentration. In prokaryotes, the passage of electrons is accompanied by the outward movement of protons across the plasma membrane.

Curriculum Framework

Inner mitochondrial membrane

Outer mitochondrial membrane

Electron transport chain

Electron carrier (NADH)

Electrons

Oxygen Electrons

Hydrogen ions

Water

Hydrogen ions

Inner mitochondrial membrane

Area of high hydrogen ion concentration

ATP synthase ATP

Inner mitochondrial membrane

Outer mitochondrial membrane

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 the enzyme, ATP synthase

• ATP synthase uses the exergonic flow of H+ to

drive phosphorylation of ATP

• This is an example of chemiosmosis, the use of

energy in a H+ gradient to drive cellular work

Figure 9.14

INTERMEMBRANE SPACE

Rotor

Stator H

Internal

rod

Catalytic

knob

ADP

+

P i ATP

MITOCHONDRIAL MATRIX

Figure 9.15

Protein complex of electron carriers

(carrying electrons from food)

Electron transport chain

Oxidative phosphorylation

Chemiosmosis

ATP synth- ase

I

II

III

IV Q

Cyt c

FAD FADH2

NADH ADP P i NAD

H

2 H + 1/2O2

H

H H

2 1

H

H2O

ATP

• The energy stored in a H+ gradient across a

membrane couples the redox reactions of the

electron transport chain to ATP synthesis

• The H+ gradient is responsible for establishing

a proton-motive force, emphasizing its

capacity to do work

Mitochondrial Membrane

• Name and describe three structural features that make the mitochondrial membrane effective at the process of energy transfer.

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ATP Production by Cellular Respiration

Arrange these in order of energy transfer from start through chemiosmosis:

• electron transport chain

• Glucose

• proton-motive force

• NADH

• ATP

Figure 9.16

Electron shuttles span membrane

MITOCHONDRION 2 NADH

2 NADH 2 NADH 6 NADH

2 FADH2

2 FADH2

or

2 ATP 2 ATP about 26 or 28 ATP

Glycolysis

Glucose 2 Pyruvate

Pyruvate oxidation

2 Acetyl CoA

Citric acid cycle

Oxidative phosphorylation: electron transport

and chemiosmosis

CYTOSOL

Maximum per glucose: About

30 or 32 ATP

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