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35 Cards in this Set

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  • Back
How are the complexes n the ETC arranged?
Order of increasing ability to accept e-
What is the ultimate oxidizer?
What is reduction? What is oxidation?
Reduction: Gain e-
Oxidation: Lose e-
How do you measure Eo?
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)
How do you calculate Eo?
Eo= Eo (oxidant) -Eo (reductant)
(oxidant=oxidizing agent,reductant=reducing agent)
dG= -nFEo
Where are H+ pumped in the ETC? How?
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
Where do the e- from NADH go? From FADH2?
NADH: go to complex I in the IMM, then to complexesIII & IV
FADH2: Go to complex II, then III & IV
How many ATP do you make per NADH? Per FADH2?
What are the ETC complex blockers? What complex do they block? How can they be bypassed/
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
What happens when B-hydroxybutyrate is added to mitochondria?
[Oxygen] decreases
B-hydroxybutyrate intiates NAD-linked oxidation
What is the P/O ratio?
# of ATP molec/ (1/2)O2
# of ATP molec/ NADH
# of ATP molec/ FADH2
Describe the complexes of the ETC.
-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
What are the 2 shuttles in the ETC? What do they do?
-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
How do e- move from one redox center to another?
Bridge 2 heme groups tog and use the polypeptide backbone and side chains of the complezes for e- transport
What is an anaplerotic rxn?
Reactants that feed interm into the CAC (ex: pyruvate carboxylase and AA metabolism)
What happens when aa are fed into the CAC?
-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
What mediates ATP synthesis in the mito?
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
What evidence supports the chemiosmotic theory?
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
What are some examples of uncouplers? How do they work?
-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)
What is the mechanism of Brown's fat cells?
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)
How are H+ transferred from matrix to IMS?
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)
Describe the F0/F1
-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
What is the composition of the F0 subunit of the ATP synthase?
-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
Which compounds block the H+ chnnel?
-Oligomycin: blocks reversibly
-Dicyclohexylcarbo-di-imide: blocks H+ channel irreversibly
What happens when the H+ channel of the ATP synthase is blocked?
Inhibits ATP synthsis because the C12 rotor won't be able to turn and this stops the Beta catalytic subunits of F1
What is the differnce between uncouplers and blocking the H+ channel?
-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
What subunit is involved in the direct synthesis of ATP?
Beta-catalytic subunit of F1
What are the 3 states of the Beta catalytic subunit?
-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
How does the beta catalytic subunit work?
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)
What is the point of teh H+ gradient for ATP synthesis?
-used for rotational catalysis (H+ gradient facilitates the transition of conformational states)
-not directly used for rxn to synthesize ATP
How are ADP and Pi transported into the mito?
-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)
Why are mito so important?
-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)
What are the three main Reactive Oxygen Species?
-Superoxide Anion
-Hydrogen Peroxide
-Hydroxyl Radical
How is the superoxide anion created?
--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
How is hydrogen peroxide formed? How is it neutralized?
-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