Chapter 20 - The ETC Flashcards
oxidative phosphorylation
metabolic pathway that uses energy released by the oxidation of nutrients to produce ATP
oxidative phosphorylation occurs in…
inner membrane of mitochondria
final electron acceptor
O2
electron donors
NADH and FADH2
4 parts of the mitochondria
- outer membrane
- inner membrane
- intermembrane
- matrix
Is the outer or inner membrane permeable to small molecules/ions?
outer; inner requires specific transporters
chemiosmotic theory
- energy is released as electrons flow through the electron transport chain, energy is used to transport protons across the inner mito. membrane
- this generate potential energy, pH gradient and electrochemical potential across the inner mito. membrane
- protons flow back across the membrane down this gradient, through ATP synthase
- ADP + Pi –> ATP
electron carriers of the ETC
- NADH and FADH2
- Ubiquinone (coenzyme Q)
- cytochromes (a,b,c)
- iron-sulfur centre-containing proteins
ubiquinone (coenzyme Q)
- lipid soluble
- diffusible in lipid bilayer
- shuttles e- between less mobile e- carriers in a membrane
- accepts 1 or 2 e-
cytochromes
proteins that function as electron carriers
cytochrome c
- soluble protein
- carries one e-
- associates with outer surface of inner mito. membrane
heme
prosthetic group of cytochromes (carry the e-)
-iron present as oxidized (FE3+) or reduced (Fe2+)
How are electrons passed in heme?
they are passed by the reduction of Fe3+ to Fe2+, back to Fe3+
proteins with iron-sulfur centers
2 iron atoms joined by 2 atoms of inorganic sulfur, linked to a protein by the amino acid cysteine.
One protein can have ______ iron-sulfure centers.
several
Proteins associated with ETC Complex I
NADH dehydrogenase; Fe-S proteins
Proteins associated with ETC Complex II
Succinate dehydrogenase, Fe-S proteins
Proteins associated with ETC Complex III
Cytochrome C oxidoreductase, Fe-S proteins
Proteins associated with ETC Complex IV
cytochrome oxidase; Cu-S (cos) proteins (similar to Fe-S protein centers)
Complex I: NADH dehydrogenase
- several Fe-S centers
- L shaped, one arm in matrix (N side), one in the membrane (P side)
- rxn: 2 e- reduction by by ubiquinone
Complex II: Succinate Dehydrogenase
- oxidizes succinate to fumarate, transfers e- to ubiquinone –> QH2
- e- of from succinate –> FAD –> Fe-S centers –> ubiquinone –> reduce it to QH2 (ubiquinol)
- no H+ are moved across inner mito. membrane
Complex III: Cytochrome C oxidoreductase
- present in inner mito. membrane
- transfer e- from ubiquinone –> cytochrome C
- transports protons from matrix to inter membrane space
- contributes to proton gradient N side
Complex IV: cytochrome c oxidase
- integral membrane protein, inner mito. membrane
- carries e- from cyt c to O2, which is reduced to water
- pumps H+ across the membrane
- O2 is the final e- acceptor (requires 4 e-)
Proton Motive Force
energy conserved from the electrochemical gradient created from movement of protons during e- transfer
2 components of proton motive force
chemical potential energy and electrical potential energy
chemical potential energy
a difference in proton conc. (a pH gradient)
electrical potential energy
difference in electrical charge across the membrane, with the N side having a neg. charge
What provides the necessary energy for ATP synthesis?
the flow of protons down their electrochemical gradient