METC & Oxidative Phosphorylation Facts

The METC and Oxidative Phosphorylation Processes Occur in the

Inner Mitochondrial Membrane

Lipid Soluble Coenzyme

UQ, CoQ

Water Soluble Protein

cyt c

A lipid soluble coenzyme and a water soluble protein shuttle…

Shuttle between protein complexes

Complex 1: NADH-CoQ Reductase

NADH > UQ; 4 H+ Transported out per e-

Complex 2: Succinate-CoQ Reductase

Succinate Dehydrogenase (from TCA Cycle) + UQ > Fumarate + UQH2

Complex 3: CoQ-Cytochrome c Reductase

CoQ passes e- to cyt c (and pumps H+) during the Q Cycle

Complex 4: Cytochrome c Oxidase

Electrons from cyt c are used in a four-electron reduction of O2 to produce H2O (Oxygen is the terminal acceptor of e- in the ETC); also transports H+

ETC and Oxidative Phosphorylation Coupling

The proton gradient across the inner mitochondrial membrane could be used to drive ATP synthesis

ATP Synthase is inhibited by

Oligomycin and DCCD

Complex 1 Inhibitor

Rotenone

Complex 4 Inhibitor

Cyanide, Azide, and CO

Uncouplers

Hydrophobic molecules with a dissociable proton; Disrupt the tight coupling between ETC and Oxidative Phosphorylation by dissipating the proton gradient; Shuttle back and forth across the mitochondrial membrane, carrying protons to dissipate the gradient

ATP is transported out of the mitochondria via

ATP-ADP Translocase; ATP Out + ATP In = H+ in; ATP Out is favored b/c cytosol is + relative to the - matrix

Every ATP transported out costs

1 H+; therefore Making and exporting 1 ATP = 4 H+

ETC yields (from NADH)

10 H+ per Electron Pair from NADH > Oxygen

How many H+ flow back into the matrix?

4 per ATP

FADH2 Yields How Many H+?

6 H+ are pumped per electron pair to oxygen

Electron Shuttle Systems

Carry e- without carrying NADH

Glycerophosphate Shuttle

Stores electrons in Glycerol-3-P which transfers e- to FAD

Malate-Aspartate Shuttle

Uses Malate to carry e- across the membrane