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

2. 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

3. Main Reactants: NADH FADH2 O2
ETC
Main Reactants:
NADH
FADH2 O2

4. ETC
Main Products:
ATP
H2O

5. 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)

6. 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

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

8. 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

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

10. 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