Oxidative Phosphorylation: ETC and Chemiosmosis

• etc = electron transport chain

  • helps electron carriers to do their jon

• NADH = 3 ATP

• FADH2 = 2 ATP

Names of Proteins and Electron Carriers

• I = NADH dehydrogenase

• II = Succinate dehydrogenase

• III = Cytochrome b-c1 complex

• IV = cytochrome oxidase complex

• Q = coenzyme Q

• cyt c = cytochrome C

Electron Transport Chain

• NADH and FADH2 transfer electrons to a series of proteins in inner mitochondrial membrane

• highly exergonic- free energy used to move H+ across membrane

  • protein gradient across inner membrane

Steps

1. I picks up H+ (2e) from NADH, NADH oxidized to NAD+

2. Q strips e, I lets of of H+, H+ moves to inter membrane space

3. Q moves e to III, Q is oxidized, III is reduced, III pumps one proton into inter membrane space

   1. as electrons move between molecules, they occupy more stable positions

   2. free energy used to move H+ against concentration gradient across mitochondrial membrane to mitochondrial matric

4. cytochrome C moves 2e to IV, IV pumps one H+ into inter membrane space

   1. free energy released to move H+

5. IV catalyzes reaction between e, p and O2 —> H2O

   1. requires extremely electronegative substance (O2) to oxidize last protein, e are very stable

   2. O2 + 2p from matrix —> H2O

   3. aerobic process

Chemiosmosis

• ETC creates ECG that stores free energy

• H+ cannot diffuse through phospholipid bilayer

Steps

1. free energy from ECG moves protons through ATP synthase

2. energy converts ADP + Pi —> ATP

3. ATP transported through mitochondrial membrane by facilitated diffusion —> cell cytoplasm

   1. drive endergonic processes (movement, active transport, synthesis)

NADH vs FADH2