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64 Cards in this Set
- Front
- Back
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What is the purpose of the ETC?
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To create a chemical and pH gradient across the mito INNER membrane, storing energy.
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What do electrons flowing thru the ETC eventually do?
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Reduce O2 to water.
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What is the work done by electron flow?
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Pumping of protons out of mito matrix into innermembrane space.
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Why is the mito inner membrane a good place for the ETC? (2 reasons)
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1. ATP synthase and ETC carriers are embedded in it.
2. It is impermeable to chrgd molecules - metabolites only cross if they have a carrier. |
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How do metabolites get into the outer membrane of mitochondria?
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It is porous - they diffuse
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How does Pi get into the mito matrix?
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By symport transport with H+ - set up by PMF set up by ETC.
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How does ADP get into the matrix for ATP synthesis?
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It is exchanged for ATP by an exchange transporter
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What factor will limit the uptake of ADP?
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Low ATP - if it's not available for exchange.
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What is the charge of the matrix with respect to the intermembrane space?
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Negative
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What are the 2 shuttles for getting NADH into the matrix?
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-Glycerol Phosphate shuttle
-Malate-aspartate shuttle |
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What happens to NADH at these shuttles?
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The electrons are transferred to the matrix, but not NADH itself.
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Glycerol phosphate shuttle:
-Rev/irrev? -Where? -Yield? |
-Irreversible
-Skeletal muscle & brain -Yields FADH2 inst of NADH |
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Malate-Aspartate shuttle:
-Rev/irrev? -Where? -Yield? |
-Irreversible
-Liver and Heart -NADH |
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How does the Glycerol-3-P shuttle work?
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1. NADH reduces DHAP -> G3P
2. Integral membrane G3P dehydrogenase remakes DHAP; e- go to Ubiquinone in membrane. |
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Why is the Malate-Asp shuttle better than Glyc3Phosphate?
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Malate takes the electrons of NADH directly into the matrix.
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How do the electrons get from NADH to malate? Enzyme?
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NADH oxidizes Oxaloacetate via Cytosolic Malate Dehydrogenase
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How does Malate get into the matrix?
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It gets exchanged for a-KG.
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What happens to Malate once inside the matrix? Enzyme?
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Malate gets reoxidized by Mitochondr Malate Dehydrogenase - remakes Oxaloacetate and NADH
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What is necessary for the Mal-Asp shuttle to be complete?
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Oxaloacetate converted to Asp which can transport to cytosol.
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What allos Asp transpot from the matrix to the cytosol?
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It gets exchanged for Glutamate.
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How is glutamate useful in the matrix?
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It accomplishes 2 things:
-Converts OAA to Asp (vital) -That converts Glu -> aKG (which exchanges for Malate (step 1) |
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So what 2 membrane exchanges take place?
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1. Malate in for a-KG out
2. Asp out for Glutamate in |
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What is an important point about Mitochondrial Malate Dehydrogenase?
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It is the same enzyme used in the last step of TCA.
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What are the major differences between NAD+ and FAD?
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-When oxidized, NAD+ is pos charged; FAD is neutral.
-NAD+ only able to gain 2- -FAD is able to gain 1 OR 2 |
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3 types of electron carriers in the mito inner membrane:
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-Ubiquinone (coenzyme Q)
-Iron-sulfur clusters -Cytochromes |
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What are the important features of Coenzyme Q?
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-A component of Complex I
-Accepts 1 or 2 electrons |
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What are the important features of Iron Sulfur clusters?
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Iron can be ferric or ferrous
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Where are Cytochromes found?
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In all electron transport complexes
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Which cytochrome is especially important?
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Cyt-c - carries e- between complexes III and IV.
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What's a good way to remember that Ubiquinone is in the inner membrane?
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It's very greasy so it likes to live among lipids.
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How many electrons can Iron Sulfur clusters carry?
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Only one at a time.
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How do the various cytochromes differ?
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in their side chains.
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What is the important component of cytochromes that carries e-?
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Heme
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What terms describe the simultaneous redox rxns accomplished by ETC?
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NADH oxidation: EXERGONIC
ATP production: ENDERGONIC |
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DeltaG of NADH oxidation:
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-52
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DeltaG of ATP synthesis:
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+7.5
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How does the energy of NADH get couple to ATP synthesis?
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As e- flow through ETC protons get pumped out and establish a proton gradient.
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What is the deltaG of this proton pumping?
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Positive - it uses some of the energy in NADH.
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What balances the loss of energy by proton pumping?
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Electrons flow to progressively more easily reduced carriers.
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How many protons get pumped by:
-Complex I -Complex III -Complex IV |
I = 4
III = 2 IV = 4 |
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How many protons get pumped per
-NADH -FADH2 |
10 for NADH
6 for FADH2 |
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Why only 6 protons for FADH2?
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It bypasses Complex I and passes its electrons directly to Ubiquinone.
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What reaction happens at the end of the ETC?
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1/2O@ + 2 H+ -> H2O
But Complex IV waits until there are 4 e- so really 1 O2 -> 2H2O |
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How do E'v and delta G change as electrons flow through ETC?
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E'v gets more pos
DeltaG gets more neg -Hence reduction of electron carriers gets easier. |
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How many protons does it take to make an ATP?
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4
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What is the name of Complex II? What pathway is this in?
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Succinate dehydrogenase - in the TCA cycle
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What does Succinate dehydrogenase do?
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Takes the FADH2 made in converting Succinate to Fumarate, and gives the electrons to the ETC directly!
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When are redox reactions thermodynamically favored?
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When electron flow is toward species with more positive E.
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What is the equation for converting Delta E to G?
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G = -nFE
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What has a higher absorbance; NADH or NAD+? Cyt CFe2+ or Fe3+?
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NADH
Fe2+ |
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So in general what is the effect of oxidation on a molecule's absorbance?
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Reduces it.
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What happens to e- flow through ETC when [H+] of intermembrane space is high?
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It ceases - protons can't get pumped out until ATP synthesis reduces the gradient.
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Re: mitochondria, what is
-State 3 -State 4 |
State 3 = normal working
State 4 = normal resting |
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What is the rate limiting factor for a normal working mitochondria?
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The Respiratory chain - electrons can only flow so fast thru the ETC.
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What will the steady-state % reduction of e- carriers in ETC be in
-State 3 -State 4 |
3: progressively less reduced (53, 20, 16, 6, 4)
4: Still progressively less reduced, but more reduced than for state 3 (99, 40, 35, 14,0) |
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What is the rate limiting factor for state 4 resting mitochondria?
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ADP - Respiration rate is slow b/c ATP is not being burned so ADP levels are low
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What will be the effect on e- carriers if oxygen is unavail?
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The steady state % of reduction will be 100% for all - they are all fully reduced.
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What will be the effect on e- carriers if NADH is unavailable?
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All will be fully oxidized - 0% reduced.
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What are the symptoms of Complex III defect due to partial deficiency?
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Myopathy
-Muscle weakness -Lactic acidosis -Decr. phosphocreatine levels |
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What poisons inhibit complex IV reversibly?
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Cyanide CN
Carbon Monoxide CO |
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What poison inhibits complex IV irreversibly?
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Nitric Oxide NO
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What else does Nitric Oxide inhibit?
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Destroys FeS centers of complexes I and II (at high levels)
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What drug inhibits complex III?
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Antimycin A
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What 2 drugs inhibit Complex I?
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Rotenone
Amytal |
