M2b L13 Flashcards
(9 cards)
Explain what is meant by oxidation-reduction potential
electrons are being extracted from food and put into NAD+ making NAD+ + H+
electrons are carried over from one carrier to the next, electrons hop over, next one has a slightly stronger affinity, electrons hop over until it reaches the oxygen
measure of the ability of a biochemical system to oxidize or reduce
Outline the connection between oxidation-reduction potential and free energy
little bits of free energy are released during each step of the ETC, results in conservation of energy, used to make ATP
Explain why electrons from NADH/H+ or FADH2 can be accepted by oxygen
because they deliver them down the transport chain
Describe the four membrane-bound complexes of the mitochondrial electron transport chain
complex I: entry point for NADH/H+, pumps 4 protons, energy released is used to pump protons to other side of membrane
complex II: succinate dehydrogenase (FADH2) shuffles electrons, gets protons to UQ. UQ takes 2 protons and electrons for succinate
complex III: accepts e- from mobile carrier UQ (1 to 3 or 2 to 3) several electrons carriers, releases energy, pumps 4 protons
complex IV: accepts e- from cytochrome c pumps 2 protons, electrons end up on O2
Describe the mobile electron carriers
Ubiquinone (UQ): moves freely in the membrane in a hydrophobic environment (moves electrons 1 to 3 or 1 to 2)
Cytochrome c, moves electrons 3 to 4, moves along the surface of the membrane on the side where the protons accumulate
Describe the pathway of electron transfer through the mitochondrial electron transport chain and where this is linked to H+ translocation
TCA cycle can only work if there is NADH/H+ and FAD available so it can take up the electrons, NADH/H+ and FADH2 are re-oxidized during ETC, electrons are removed, recycle them as NAD+ and FAD they go back to the TCA and it can continue
Explain why complex II does not contribute to the electrochemical gradient
There is insufficient free energy available as the electrons are transferred from FADH2 to ubiquinone because of Coenzyme Q
Describe the electrochemical gradient and explain how it is formed across the membrane as a result of electron transport
gradient is formed from energy released during e- transfer the protons make the intermembrane space more acidic, external face +ly charged, more protons, matrix face -ly charged
Describe the effect of specific inhibitors of the electron transport chain
Inhibitors block oxidation and reduce both ATP generation and oxygen consumption
Specific inhibitors can block electron flow at each complex
Rotenone at complex I prevents transfer of e- UQ (does not fully affect the ETC, get electrons from CIII)
Halothanes at complex I prevents transfer of e- UQ
Antimycin A (antibiotic) inhibits complex III
Cyanide, CO bind to Complex IV
