The Electron Transport Chain

1) The electron transport chain is used to generate ATP (energy) in most organisms- both prokarytoic and eukaryotic.

2) NADH and FADH2 generated from glycolysis, pyruvate oxidation and the citric acid cycle are used to pump protons across a phospholipid bi-layer membrane

3) In eukaryotes the protons are pumped across the inner membrane of the mitochondria, in prokaryotes (bacteria) the protons are pumped across the cell membrane

Diagram of the electron transport chain

4) This accumulation of a concentration gradient of charged protons on one side of a membrane is a great store of potential energy and is referred to as the proton motive force.

5) Protons are pumped as electrons are donated from NADH and FADH2 to proteins that are embedded in the membrane. These electrons pass through a series of proteins- thus the name: electron transport chain.

6) The electrons ultimately combine with O2 and protons to make water. Oxygen (O2) is the final electron acceptor


7) ATP is generated chemiosmotically as the protons move back down the concentration gradient through ATP Synthase which then phosporylates ADP to ATP.

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