BLG 143 Study Guide - Final Guide: Atp Synthase, Intermembrane Space, Oxidative Phosphorylation
27 Apr 2018
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9.6 Electron Transport & Chemiosmosis: Building a Proton Gradient to Produce ATP
Electron Transport Chain ETC
➢ Occurs in the inner mitochondrial membrane (eukaryotes) or the cell membrane
(prokaryotes)
➢ Electrons donated by NADH and FADH2 transported along a chain of protein
acceptors, increasing sequentially in electronegativity
➢ Oxygen acts as a final electron acceptor, becoming reduced to water
➢ Flow of electrons through proteins used to drive 3 proton pumps
➢ H+ pumped to the intermembrane space of mitochondrion (eukaryotes) or outside
the cell (prokaryotes)
➢ Chemisomotic gradient drives ATP synthase to phosphorylate ADP (oxidative
phosphorylation)
➢ Net yield 34 ATP max, 29 irl
As electrons are passed from one protein to another in the chain, the energy released by
the redox reactions is used to pump protons across the inner membrane of mitochondria.
After this proton gradient is established, a stream of protons through the enzyme ATP
synthase makes part of the protein spin, driving the production of ATP from ADP and Pi
(oxidative phosphorylation).
The inner membrane of the mitochondrion also contains a molecule called ubiquinone or
coenzyme Q, that’s not a protein. Consists of a carbon containing ring attached to a long tail
made up of isoprene subunits. Structure determines molecule’s function. The tail is
hydrophobic. Lipid soluble and can move throughout the mitochondrial membrane
efficiently. All but one of the proteins in the ETC are embedded in the membrane.
Chemiosmosis Hypothesis
ETC’s real job is to pump protons from the matrix of the mitochondrion through the inner
membrane and out to the intermembrane space or the interior of cristae.
The pumping activity would lead to a buildup of protons in these areas. The
intermembrane space and the inside of cristae would become positively charged relative to
the matrix and would have a much higher [] of protons.
The result would be a strong electrochemical gradient favouring the movement of protons
back into the matrix.
An enzyme in the inner membrane uses this proton-motive force to synthesize ATP.
Chemiosmosis the production of ATP via a proton gradient
➢ In a mitochondrion, protons are pumped instead of water
➢ When protons move through ATP synthase, the protein spins and generates ATP
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Document Summary
9. 6 electron transport & chemiosmosis: building a proton gradient to produce atp. Occurs in the inner mitochondrial membrane (eukaryotes) or the cell membrane (prokaryotes) Electrons donated by nadh and fadh2 transported along a chain of protein acceptors, increasing sequentially in electronegativity. Oxygen acts as a final electron acceptor, becoming reduced to water. Flow of electrons through proteins used to drive 3 proton pumps. H+ pumped to the intermembrane space of mitochondrion (eukaryotes) or outside the cell (prokaryotes) Chemisomotic gradient drives atp synthase to phosphorylate adp (oxidative phosphorylation) Net yield 34 atp max, 29 irl. As electrons are passed from one protein to another in the chain, the energy released by the redox reactions is used to pump protons across the inner membrane of mitochondria. After this proton gradient is established, a stream of protons through the enzyme atp synthase makes part of the protein spin, driving the production of atp from adp and pi (oxidative phosphorylation).
