Chapter 20: The Electron Transport Chain

Do Problems 1,2,4,6,8-13,16,17,19.

Web Site: www.ccrc.uga.edu/personnel/personnelframe.html

Russell W. CarlsonTEL: 542-4439EMAIL: rcarlson@ccrc.uga.eduLocation: Rm2043, Complex CarbohydrateResearch Center, 315 Riverbend Rd.

Overview of oxidative phosphorylation

NADH

Glc → 2 Pyr → 2 Acetyl‐CoA   2ATP + 2NADH

2ATP + 2NADH6NADH 2QH2

6CO2

2ATP

Glycolysis

TCA

20.1 OxPhos Takes Place in The Mitochondrion

Innermembrane

Outermembrane

Matrix

20.2 OxPhos Depends on e- Transfer•Protonmotive force is the energy created by the proton concentration gradient formed across the mitochondria inner membrane.

•H+ flow forms a circuit (similar to an electrical circuit).Energy Potential Across Membrane is Formed by a Proton GradientX- + H+ → X + ½H2

X- → X + e-

H+ + e- → H2

Go’ = -nFE’0n = number of electrons

translocated; 2

F = Faraday’s Constant, 96.48 kJ/mol/V, or 23.06 kcal/mol/V

e- Transport Chain Components and Energetics

Dow

nhill E

nerg

y Pr

oces

s

NADH + ½O2 + H+ → H2O + NAD+

E’0½O2 + 2H+ + 2e- → H2O +0.82V

NAD+ + H+ + 2e- NADH -0.32V

Go’=-nFE’0= -2(96.48 Kj/mol/V)

(0.82V – (-0.32V))

= -2(96.48Kj/mol/V)(1.14V)

= -220Kj/mol = 52.6kcal/mol

Overall Net Reaction

Iron-sulfur proteins: non-heme, different chemical environments = different electrochemical potentials

Fe2+ Fe3+ + e-

Cu+ Cu2+ + e-

Cytochromes: Heme-proteins

Isoprene unit

Ubiquinone

20.3 ETC, Proton Pumps & Citric Acid CycleNADH + Q + 5H+

MATR → NAD+ + QH2 + 4H+IM

From matrix

From citricacid cycle

I

III

IV

II

QH2 + 2Cytcox+ 2H+MATR → Q + 2Cytcred + 4H+

IM

2QH2 + Q + 2Cytcox+ 2H+MATR

2Q + QH2 + 2Cytcred + 4H+IMCytb Cytb

4Cytcred+ 8H+MATR + O2 → 4Cytcox + 2H2O + 4H+

IM

4 protons transported

2 protons used from matrix and 4 transported

4 protons/2e- used from matrix and 2 protons/2e- transported to IM

Summary

Go’=-nFE’0 = -231.8 kJ/mol

4H+MATR + O2 → 2H2O

Go’=-nFE’0 = -4(96.48 kJ/mol/V)(0.82V)= -316.45 kJ/mol.

Cytc oxidase uses extra energy to

transport 4 protons to IM

Overall Summary of ETC

Electron Transport

ProtonPump

ETC Leads to Toxic Reactive Oxygen Species (ROS)O2 O2

- . O22-e- e-

Superoxide ion Peroxide

Reacts with and damages:Proteins, nucleotide bases, membranes, etc.

2O2-. + 2H+ → O2 + H2O2Superoxide dismutase

2H2O2 → 2O2 + 2H2O Catalase

Antioxidants: vitamin E, C, ubiquinol, etc.

ROS: Signal Transduction, Channels, TSs, etc., pathogen defense