Term
| Role of oxidative phosphorylation |
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Definition
| Role is to generate energy, in the form of ATP, from the flow of electrons from a reducing agent (NADH or FADH2) to a more stable carrier (oxygen accepting the electrons and being reduced to water). Energy is released as the electrons flow to their most stable form; the energy released is captured as chemical energy in the formation of the high energy bonds of ATP. |
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Term
| How is energy captured in ox phos? |
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Definition
| The energy is captured in the form of a proton gradient across the inner mitochondrial membrane. Proton flow down its electrochemical gradient is favorable, and will drive the synthesis of ATP. |
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Term
| How is energy yield calculated? |
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Definition
deltaGo = - (n)(F)(deltaEo)
n = # of electrons being transferred
F = Faraday constant (23 kcal/mol-volt)
deltaEo = Change in “Redox” potential under standard conditions (all reactants at 1.0 M concentration).
The redox potential measures a substrates affinity for electrons as compared to a standard reaction. The standard reaction is shown below:
2H+ + 2e- --> H2 Eo = 0 V |
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Term
| What determines sign of Eo? [electrochemistry] |
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Definition
If an electron donor is a STRONGER donor than H2, then Eo will be negative.
For those compounds which will ACCEPT electrons from H2, Eo will be positive. |
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Term
| Two states of Coenzyme Q (CoQ) |
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Definition
| CoQ can carry either one or two electrons; in the one-electron state it will be a radical. CoQ is derived from acetyl-CoA. |
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Term
| Other names for complex I |
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Definition
| NADH dehydrogenase or NADH:CoQ oxidoreductase |
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Term
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Definition
| Complex I contains 6-7 Fe-S complexes and one FMN complex. Complex I can transfer two electrons at a time, and donate either one or two at a time to CoQ. Two pairs of protons are ejected for each pair of electrons entering the chain at complex I. |
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Term
| Another name for complex III |
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Definition
ubiquinol-cytochrome c
oxidoreductase |
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Term
| another name for complex IV |
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Definition
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Term
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Definition
| Cytochrome C donates electrons, one at a time, to Complex IV, which contains two copper containing electron carriers and two iron containing carriers, cytochromes a1 and a3. The copper alternates between the Cu+1 and Cu+2 states as the electrons are passed along the chain. Once four electrons are collected within complex IV, oxygen can be reduced to water. |
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Term
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Definition
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Term
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Definition
Complex II is the entry site of FADH2 from the TCA cycle into the electron transfer chain. FADH2 is not as strong an electron donor as NADH, so it enters later in the chain than does NADH.
Complex II donates directly to coenzyme Q, one or two electrons at a time.
Note the LACK of proton extrusion at complex II. The energy transfers are too low to push electrons out of the matrix. |
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Term
| Number of protons extruded by each complex |
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Definition
| 4 by complex I, 0 by complex II, 4 by complex III, and 2 by complex IV |
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Term
| proton motive force (PMF) |
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Definition
PMF is the force is generated across the inner mitochondrial membrane and consists of two components:
delta pH (pH in matrix > pH innermembrane space)
delta psi ([protons] in matrix < [protons] innermembrane space)
These two components lead to an electrochemical gradient of protons being established across the inner mitochondrial membrane. |
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Term
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Definition
delta G = PMF = 2.3 RT (delta pH) + ZF(delta psi)
R = gas constant = 1.98 cal/mol-degree
T = temperature in degrees Kelvin
Z = electrical charge (1 for electron)
F = Faraday’s constant (23 kcal/mol-volt)
delta pH = approximately 0.75 units
delta psi = approximately 170 mV (outside positive) |
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Term
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Definition
| Uses energy from proton flow across F0 subunit to synthesize ATP. Has two parts; F1 is the headpiece (in matrix) and F0 is membrane embedded and has the pore. ATP synthesis occurs on alpha and beta subunits. |
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Term
| How does oligomycin block ATP synthesis |
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Definition
| By blocking the proton channel |
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Term
| How does ATP synthase work |
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Definition
| As H+ travels down its electrical gradient, the a-b subunits rotate, and bound ATP is released. The bound ADP + Pi is converted to bound ATP, and the new exposed dimer binds ADP to initiate a new round of ATP synthesis. Making the ATP is reversible; it is the release of ATP which requires energy. |
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Term
| Principles of Chemiosmotic Hypothesis |
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Definition
The electron transfer chain must be asymmetrically oriented across the membrane such that protons are ejected.
Mitochondria must be capable of ejecting protons in the presence of substrate and oxygen.
Permeabilizing membranes to protons should disrupt oxidation and phosphorylation.
The mitochondria must contain a proton driven ATP synthase. |
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Term
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Definition
| The number of molecules of ATP generated per atom of oxygen consumed in the electron transport chain. Because two electrons are transferred down the chain per oxygen atom reduced, the P/O ratio also reflects the ratio of ATPs synthesized per pair of electrons consumed |
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Term
| P:O ratio from NADH and FADH2 |
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Definition
From NADH P:O is 2.5
From FADH2 P:O is 1.5 |
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Term
| Why are NADH shuttle systems used? |
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Definition
| Because IMM is impermeable to NADH. |
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Term
| Glycerol 3-phosphate shuttle |
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Definition
| NADH in the cytosol transfers electrons to FAD in mitochondria – 1.5 ATP per cytosolic NADH (skeletal muscle, brain) |
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Term
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Definition
| Malate-aspartate shuttle – NADH in the cytosol eventually transfers electrons to NAD+ in the matrix – 2.5 ATP per cytosolic NADH (liver) |
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Term
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Definition
| Dissipate proton gradient by allowing membrane to become permeable to protons. ATP synthesis cannot function, but respiration continues at a greater rate to attempt to re-establish the proton gradient. |
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Term
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Definition
| A natural uncoupler found in brown fat, which is activated by norepinephrine. Activation of this protein (also known as UCP1, uncoupling protein 1) allows dissipation of the proton gradient to allow heat to be generated. Predominant in newborns. |
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Term
| How can one block ox phos? |
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Definition
Block electron flow along the chain.
Block the activity of the ATP synthase.
Allow free ion flow across the inner mitochondrial membrane. |
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Term
| ETC Inhibitors with sites within ETC |
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Definition
CN, CO (complex IV)
Antimycin A (complex III)
Rotenone (complex I)
Amytal (complex I) |
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Term
| ETC inhibitors that affect ATP Synthase |
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Definition
Oligomycin (block proton entry)
DCCD (block proton entry) |
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Term
| ETC inhibitors that affect uncouplers |
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Definition
CCCP (permeable to protons)
DNP (permeable to protons)
Valinomycin (permeable to potassium ions)
Thermogenin (permeable to protons) |
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Term
| ETC inhibitors that affect ATP/ADP exchange |
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Definition
| Atractyloside (blocks ADP entry into the mitochondria) |
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Term
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Definition
| ATP synthesis is regulated by the availability of ADP. The ADP enters the Matrix using an ATP/ADP exchanger, which is inhibited by atractyloside. Phosphate entry is also required, which occurs via symport with protons |
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Term
| How is ox phos regulated? |
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Definition
| It is regulated by Energy Charge. Values range from 0 to 1. Normal value is 0.8. If the value is less than 0.8, energy production is stimulated. If the value is greater than 0.8, ADP supplies in the mitochondria become rate limiting for ATP production, and production ceases |
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Term
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Definition
| Flavin mononucleotide; derived from Riboflavin; involved in Complex I |
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Term
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Definition
| ubiquinol; reduced form of CoQ |
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Term
| How many protons are extruded with FADH2 |
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Definition
| Six protons b/c start with complex II |
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Term
| Why G3P shuttle and Malate-aspartate shuttle result in different amounts of ATP generated |
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Definition
| In G3P shuttle, NADH transfers electrons to FAD in mito, which transfers electrons to Complex II. This is a very rapid system but lose energy b/c skipping Complex I. Malate-aspartate shuttle doesn’t have an actual transfer of NADH molecules; electrons are transferred from NADH to Malate to NAD+ to Complex I. |
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Term
| Why does blocking ATP synthase block oxidation? |
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Definition
| Blocking ATP synthase blocks the major route protons re-enter matrix. This enhances the proton gradient, making it so that the complexes can’t pump protons out of the matrix. This prevents oxidation. |
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Term
| Adenoside Nucleotide Transporter |
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Definition
| Antiporter; allows ATP to leave matrix while bringing in ADP |
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Term
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Definition
| symporter; brings in Pi and H+ |
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Term
| Energy yield from glucose oxidation |
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Definition
1 glucose to 2 pyruvate
Generate 2 NADH at the G3PDH step.
gives rise to 3 ATP if use the glycerol phosphate shuttle
gives rise to 5 ATP if use the malate aspartate shuttle
Generate 4 ATP by substrate level phosphorylation
1,3BPG to 3PG
PEP to Pyruvate
Must deduct 2 ATP for six carbon sugar activation
Yield from glycolysis is 5 or 7 ATP depending on the shuttle system
Overall yield from the 2 pyruvate is 25 ATP
Net total is 30 or 32 ATP depending on shuttle system |
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