Electron Transport Chain

ETC: NADH oxidation

in matrix side ; 10H+ pumped

NADH → Complex I → Q → comp III → Cyt C → comp IV → O2

ETC: FADH2 oxidation

either side ; 6H+ pumped

FADH2 → comp II → Q → comp III → cyt C → comp IV → O2

complexes I, III, IV

large multi-subunit complexes translocaze protons across IMM

routes for FADH2 oxidation

comp II in matrix side; ETF-Q oxidoreductase lipid metabolism on matrix side; g3p dehydrogenase on cystoic side

coenzyme Q

small hydrophobic electron carrier, diffuses through membrane

cytochrome c

small water soluble protein in intermembrane space

complex I electron flow

NADH + Q + 5H+N → NAD+ + QH2 + 4H+P

complex II electron flow

FADH2 + Q → FAD+ + QH2

complex III electron flow

QH2 + 2H+N + 2Cyt Cox → Q + 4H+P + 2Cyt Cred

complex IV electron flow

2Cyt Cred + 4H+N + ½O2 → 2Cyt Cox + 2H+P + H2O

flavin mononucleotide in comp I

adaptor molecule for 1 or 2 electrons

big picture

comp 1, 2, 3 pump protons into intermembrane space, 10 protons per NADH and 6 per FADH2

rotor

rotates in response to proton flow; 4 subunits

catalytic headpiece

ATP synthesis, 6 subunits and binding only occurs on beta units

stator

allow proton flow, stabilize complex in the membrane - 5subunits

beta subunit states

O - open - nothing bound

L - loose - ADP + Pi bound

T - tight - ATP bound

conformation switch O → L → T → O

how many ATP from how many protons

every 3 make one ATP, full rotation makes 3 ATP from 10 H+

carrier 1

Q located in inner membrane. can carry 1 or 2 electrons a time. transports them from comp II to comp III

carrier 2

cytochrome C located in intermembrane space. can carry 1 electron and transports them from comp III to comp IV