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35 Cards in this Set
- Front
- Back
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How are the complexes n the ETC arranged?
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Order of increasing ability to accept e-
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What is the ultimate oxidizer?
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Oxygen
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What is reduction? What is oxidation?
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Reduction: Gain e-
Oxidation: Lose e- |
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How do you measure Eo?
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Set-up 2 half cells, one with a species in sol'n with a platinum electrode, the other half-cell is the standard reference half-cell, enclosed in glass
-if e- flow from sample 1/2 cell to standard: Eo<0 -if e- flow from standard to sample 1/2 cell, Eo>0 -Neg. electrode potentials are better reducing agents -Positive elecrode otential are better oxidizing agents (i.e. O2 is a good oxidizing agent since it Eo=0.815) |
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How do you calculate Eo?
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Eo= Eo (oxidant) -Eo (reductant)
(oxidant=oxidizing agent,reductant=reducing agent) dG= -nFEo |
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Where are H+ pumped in the ETC? How?
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H+ are pumped form the mito matric into the IMS
They are pumped using the free E releasd when high E e are converted to lower e- -This elctrochemical gradient is used to synthesize ATP |
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Where do the e- from NADH go? From FADH2?
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NADH: go to complex I in the IMM, then to complexesIII & IV
FADH2: Go to complex II, then III & IV |
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How many ATP do you make per NADH? Per FADH2?
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NADH: 3ATP
FADH2: 2 ATP |
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What are the ETC complex blockers? What complex do they block? How can they be bypassed/
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Rotenone: Blocks complex I, bypass blocker by using succinate
Amytal: Blocks complex I, bypass this using succinate Antimycin A:Blocks complex III, bypass this using TMPD. e-go straigh to cyt C Cyanide: Blocks complex IV, CANNOT bypass this |
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What happens when B-hydroxybutyrate is added to mitochondria?
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[Oxygen] decreases
B-hydroxybutyrate intiates NAD-linked oxidation |
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What is the P/O ratio?
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# of ATP molec/ (1/2)O2
# of ATP molec/ NADH # of ATP molec/ FADH2 |
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Describe the complexes of the ETC.
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-Large (comp. 1 is the biggest)
-Integral mb ptns (can only be isolated by disrupting the lipid bilayer with detergent) -Contain Fe redox gps -Fe-S carry one e- at a time -Cyt. have heme gps as redox centers |
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What are the 2 shuttles in the ETC? What do they do?
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-CoQ: shuttles e= form comp I and II to Comp III
-> CoQ has a hydrophobic tail that inc its solubility in the lipid bilayer and isessential for diffusion in or across the bilayer -CytC: shuttles e- from comp III to comp IV ->has heme moiety -> peripheral mb ptn -> has additional role in apoptosis: in unfavorable conditions, cyt c is released into the cytoplasm, followed by the release of proteolytic enz which will degrade the cell from the inside out |
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How do e- move from one redox center to another?
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Bridge 2 heme groups tog and use the polypeptide backbone and side chains of the complezes for e- transport
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What is an anaplerotic rxn?
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Reactants that feed interm into the CAC (ex: pyruvate carboxylase and AA metabolism)
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What happens when aa are fed into the CAC?
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-Eventually form malate
-Transported to the cytoplasm usingmalate-aspartate shuttle -malate--> OAA in cytosol -Can use OAA as a precursor for gluconeogenesis, using PEP carboxykinase |
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What mediates ATP synthesis in the mito?
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ATP Synthase
-Free E released from e- transport is conserved through formation of an H+ gradient across the IMM by pumpoing H+out of matrix into IMS -The E derived from the H+ flowing back into the matrix is used to create ATP |
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What evidence supports the chemiosmotic theory?
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1) Ox. P req's an intact mb: leaky mb stops ATP syn
2) IMM is impermeable to ions: due to cardiolipin 3) e- transport isass't with transport of H+ out of the matrix: get charge differential 4) Reconstituion studies with bacteriorhodopsin: exp. showed that ETC and ATP Synthase are not linked, but rather are separate entities that are linked by the PMF 5) Uncoupling agents: uncouple e- transport from ATP synthesis by destroying the H+ gradient. Under high lvls of NADH, NADH will stop being oxidized if not enough O2, ADP or Pi. Normal metabolism continues hen uncouplers are added, but no ATP is made |
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What are some examples of uncouplers? How do they work?
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-DNP
-FCCP -The uncouplers pick up H+ from the cytosolic side and carry them back across the mb and release them intothe matrix .: the E from electrochemical gradient is used as heat (not to make ATP) |
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What is the mechanism of Brown's fat cells?
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1) Norepinephrine bind its receptor.
2)this stimulates adenylyl cyclase which convertes ATP to cAMP. 3) cAMP activates PKA 4) PKA P triacylglycerol lipase 5) TAG lipase-P is active and can hydrolyze Triaylglycerols to Free FA 6) Free FA combine with ATP, ADP, GTP and GDP to open the Thermogenin channel 7) H+ can now diffusesynthase. from the cytosol into the matrix 8) Free E is given off as heat (usually the purine nucs by tehmselves block the thermogenin channel) |
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How are H+ transferred from matrix to IMS?
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1) Redox loop mechanism
Has 2 criteria: -1st e- carrier has more H atoms in its reduced state then in its oxidized state (true for CoQ) -2nd e- carrier has same # of H in its reduced and oxidized states (true for CytC) 2) Proton pump mechanism 2 criteria: -Potential acid gps must be alternately fcing inside and outside of IMM as reduction and oxid take place -aa side chains have to be involved as carriers (Ptn originally has conformation with cavity facing matrix. When H+ flow into it, it changes its conformation to face IMS because of reduction with e-. When the protein is reoxidized, it gos back to its original conformation) |
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Describe the F0/F1
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-F0 is an integral mb ptn with a ptn channel. It spans the mb
-F1 projects into the matrix, is a peripheral mb ptn -F0 connects to F1 through the gamma and b (not beta) subunits -Gamma subunit: rotor -b subunit: stator -F1 has 3 catalytic subunis (beta) and 3 alpha subunits -When F1 diss't from F0, it has ATPase activity -When F1 attached to F0, ATP synthase activity |
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What is the composition of the F0 subunit of the ATP synthase?
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-A1 B2 C12
-12C: known as the rotor cuz its rotates inside the mb. This rotation is caused by an influx of H+ into the A-C subunit |
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Which compounds block the H+ chnnel?
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-Oligomycin: blocks reversibly
-Dicyclohexylcarbo-di-imide: blocks H+ channel irreversibly |
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What happens when the H+ channel of the ATP synthase is blocked?
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Inhibits ATP synthsis because the C12 rotor won't be able to turn and this stops the Beta catalytic subunits of F1
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What is the differnce between uncouplers and blocking the H+ channel?
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-Uncoupling agents: lose the H+ gradient, but ETC continues, though ATP is not made and E dissipated as heat
-H+ channel blocking: other componens in the IMM that need an H+ gradient will still function (i.e pyruvate translocase). ETC will slow down cuz pushing H+ across an ever steeper gradient |
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What subunit is involved in the direct synthesis of ATP?
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Beta-catalytic subunit of F1
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What are the 3 states of the Beta catalytic subunit?
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-L state: Loose binding of ADP + Pi, no catalytic activity
-T state: Tight binding of ADP + Pi, catalytic activity -O state: releases teh ATP produced by T-state, no catalytic activity of its own |
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How does the beta catalytic subunit work?
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C12 rotor rotates when H+ enter it. This cause gamma rotor to move. This rotation causes the Beta-subunits to change conformation
(gamma rotor is assymetric and depending on which face the gamma rotor is facing the beta-subunit, the beta subunits will have a different conformation) |
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What is the point of teh H+ gradient for ATP synthesis?
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-used for rotational catalysis (H+ gradient facilitates the transition of conformational states)
-not directly used for rxn to synthesize ATP |
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How are ADP and Pi transported into the mito?
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-Pi: uses Pi/H+ symport
-ADP: uses ADP/ATP translocator (transport ptn has 1 binding site that will bind either ADP or ATP, which causes a conf. change) |
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Why are mito so important?
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-Major sites of ATP synthesis
-Regulators of apoptsis (cyt C leaking into cytosol causes release of caspases) --Regulate glycolysis -Major site of reactive oxygen species (ROS) |
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What are the three main Reactive Oxygen Species?
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-Superoxide Anion
-Hydrogen Peroxide -Hydroxyl Radical |
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How is the superoxide anion created?
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--Happens at Comp I and btw Comp I and III of ETC
-Involves CoQ -CoQ has free radical form that acts as an intermediate in the redox loop mech, which can non-enz and easily pass e- to O2 to form the superoxide anion -Superoxide anion neutralized by Mn Superoxide Dismutase |
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How is hydrogen peroxide formed? How is it neutralized?
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-Formed from the superoxide anion
-Converted to water using Glutathione Peroxidase -In the presence of reduced transition metal ion (Fe2+), H2O2 will form a Hydroxyl Radical through the Fenton Reaction |
