Unit 2: Metabolic Processes Electron Transport and Chemiosmosis SBI4U – Ms. Richardson

Electron Transport Chain (ETC) Location: Intermembrane proteins in the mitochondria Purpose: To release the stored energy in NADH and FADH2 and use it to make ATP

Main Reactants: NADH FADH2 O2 ETC Main Reactants: NADH FADH2 O2

ETC Main Products: ATP H2O

ETC Electrons from NADH and FADH2 pass along a series of coenzymes and electron acceptors which are arranged in order of increasing electronegativity NADH dehydrogenase (weakest electron attraction) Cytochrome oxidase (strongest electron attraction)

ETC Electron carriers alternate between reduced and oxidized forms while electrons pass through each complex Electrons from NADH pass through 3 major complexes Energy from the transfer of electrons is used to pump 3 H+ out of the matrix Electrons from FADH2 pass through 2 major complexes Energy used to pump 2 H+ out of matrix An electrochemical (proton) gradient forms across the membrane, with high [H+] in intermembrane space

ETC Oxygen is the final electron acceptor Combines with 2 electrons and 2 hydrogen ions to form water

ETC After H+ concentration builds, protons diffuse back into the matrix through a channel called ATP synthase (ATPase) A proton motive force causes H+ to diffuse back into the matrix For each H+ that diffuses back into the matrix, 1 ATP is produced through oxidative phosphorylation

Chemiosmosis Process that uses the energy from proton gradients to drive the phosphorylation of ADP to form ATP

ATP Yield Theoretical Yield: Prokaryotes: 38 ATP Eukaryotes: 36 ATP Actual yield often much lower Some protons are lost through the membrane without passing through ATPase Some energy from proton gradient used to transport pyruvate Some energy used to transport ATP out of mitochondria