electron transport + oxidative phosphorylation

where does ETC occur?

inner membrane

electron transport chain

electrons flow through series of protein complexes

CO2 and NADPH are NOT involved

electrons enter through NADH and FADH2

complex I / NADH dehydrogenase

accepts electrons from NADH

pumps H+

complex II / succinate dehydrogenase

accepts electrons from FADH2

does NOT pump H+

coenzyme Q / ubiquinone

carrier 2e- between complex I + II to complex III

lipid soluble

moves freely in membrane

complex III bc1

transferes e- to cytochrome c (e- carrier)

pumps H+

cytochrome c

e- carrier

carriers e- from complex III to IV

water soluble

contains heme prosthetic group

carries 1e-

complex IV / cytochrome oxidase

reduces O2 to H2O

O2 is the final e- acceptpr

pumps 4 H+ but also uses 4H+

important cofactors

NADH, FADH2, FMN (e- acceptors)

non heme iron sulfur complex

ubiquinone

non heme iron sulfur complex

many carriers have iron-sulfur clusters

attach to cysteine R-groups in protein

sulfur also participates in active site of non heme iron proteins

isoalloxazine of FAD accepts H+ and e-

relative energy production

1 NADH = 2.5 ATP

1 FADH2 = 1.5 ATP

1 Glucose = 30 ATP

cytochromes

has protein + heme group

b,c1,a,a3

transfers e- using heme

have tetrapyrrole ring with iron

cytochrome c oxidase transfers electrons from cytochrome c→ heme a

differ in structure, absorption spectra, reduction, role in e- transport

first and final e- acceptors

1st: FMN (reduced to FMNH2 on isoalloxazine)

last: oxygen (to produce water)

what happens to reduction potential as e- move through carriers?

reduction potential increases

large change in reduction potential when electrons move from cytochrome c to oxygen

uncouplers

allow H+ to flow across inner mitochondrial membrane → inhibits ATP synthesis

ex. 2,4-DNP

cytochrome c

evolutionary trees

human vs parsnip