Biochem Muscle Weakness ATP 2
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- electron flow in ETC is driven by?
- redox potential, from most negative to most positive
- where are protons pumped in the ETC? (what complex's)
- I III IV
- What is the relationship between reduction potential and the ratio of oxidized to reduced forms of the substance?
-
more OXIDIZED means HIGHER Reduction Potential
If E'o is positive it means the substance has a higher affinity for electrons(than hydrogen electrode) - what is the relationship between delta E and delta G (equation)
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DIRECT relationship
delta G = -nF delta E
n = electrons
F = eV - what is the relationship between the reduction potentials of a system and the concentration of the oxidized and reduced forms?
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E = E'o + [RT/nF] [ln(ox/red)]
higher oxidation form means more positive potential energy - what are the electron carriers in a broader sense of the ETC
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coenzymes
specifically flavins, iron sulfur centers and hemes - what is barth syndrome?
- defect in cardiolipin, since cytochrome C is tethered to inner mitochondrial membrane by cardiolipin, a defect would lead to ETC dysfunction
- how many electrons does the ETC carry?
- 2 e
- the reduction of O2 to water often causes what to form, how do you prevent it?
- causes ROS to form, need 4 electrons to prevent formation
-
nicotinamide nucleotides are weakly bound to enz's and are therefore?
coenz prosthetic group
coenz cosubstrate
coenz cofactor -
coenz cosubstrate
most nicotinamide nucleotides are free and in equil with their enzyme substrates -
NAD and NADP
oxidants or reductants strong or weak -
weak oxidants
always accept two e and a proton - NADP is in the ox or reduced state primarily(in cells)
-
reduced state NADPH, because it functions more in anabolism
NAD is 90% oxidized state
functions more in catabolism -
flavin nucleotides are
coenz prosthetic
coenz co substrate
coenz cofactor - prosthetic groups
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COMPLEX I
mechanism -
NADH-UBQ oxidoreductase
takes two e from nadh into the FMN group, single electrons are then transfered to FeS centers and eventually to UBQ - COMPLEX II
-
Succinate dehydrogenase
takes electrons from Succinate via FAD and transfers along FeS centers - what complex's transfer electrons to ubiquinone?
-
complex I and II
glycerol 3 phosphate dehydrogenase
ETF(e transport flavoprotein)-UBQ oxidorecutase) . . .from fatty acid cycle - which complex's have heme groups?
- IV III and cytochrome C
- why does hemoglobin bind O2 and cytochromes do not?
- b/c cytochromes have amina acid side chains at some of their coordination sites, thats why they do e transfer (ox/red) instead
- what is the exception to the O2 vs ox/red situation?
- cytochrome A binds O2 AND is oxidized as a result, last cytochrome of chain
-
characteristic features of heme
A
B
C
and what structures they are found in -
A:
cytochrome C oxidase complex IV, a and a3
has a long isoprenoid chain
attaches to apoprotein thru aa coordination bond
B:
hemoglobin myoglobin, complex III
simple/plain
c:
Cytochrome C
side chains cys cov bond to protein through thioether linkage, structure is conserved, side chains met and his coordination bondsz to apoprotein - describe the heme in cytochrome a3
- coordination bonds to his and copper "B"
- describe the redox centers in complex III
-
prosthetic groups
cyt c1, cyt b, reisk fe-s
each monomer of the 11 subunit complex is pear shaped with protuberances into mito matrix and reisk/c1 protruding into intermem space -
the Q cycle
general description -
happens in complex III, UBQ-Cytochrome C oxidoreductase
reduced Q transfers e to two cytochrom C molecules, uses heme prosthetic groups as e carriers - The Q cycle in depth
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ubiquinol transfers an e to reisk which undergoes conformational change and transfers it to cyt c1
transfers an e to bL and then to bH
OVERALL 4 protons pumped into intermembrane space and 2 e transferred to the single e carrier cyt C1 - complex IV where are the three essential subunits encoded?
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mitochondrial DNA
remaining 10 are in nuclear DNA - subunit 1
- 12 transmem helices
- subunit II
- binds cyt c, large domain protruding into cytosolic face of inner membrane
- complex IV how does it work
-
cyt c transfers e to Cu.A
Cu.A transfers to heme a
heme a transfers to binuclear center (heme a3-Cu.B)
binuclear center transfers to O2 using two H from matrix to make water (this helps with the proton grad)
overall 4 protons pumped into intermem space, - overall how many protons go to the cytosol for every 4 pumped taken up from the matrix
- 2
- what is a negative effect of repurfusion of oxygen to ischemic areas after a myocardial infarction?
- formation of ROS reactive oxygen species
-
how do you make superoxide
hydrogen peroxide
hydroxyl radical -
superoxide, add an e to O2
H2O2, add 2 H and e to superoxide
OH, add a e and H to H2O2, makes water and OH radical - how does the cell defend against ROS
- superoxide dismutase and catalase
- what do superoxide dismutase and catalase do biochemically
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superoxide: converts 2 superoxides to H2O2 and oxygen
catalase: converts 2 H2O2 to water and oxygen
NOTE: hydroxyl radical can from from H2O2 by addition of an e and H, This radical is converted to water by adding another e and H - what types of groups do iron sulfide compounds come in?
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2,3,4 or 8 irons in the same protein
8 irons carry 2 e, everything else carries 1 - what is the defining property of ubiquinone in chemical structure
- long hydrophobic side chain that allows it to be free in the lipid core of the mem
- what are the two broad categories of flavin nucleotides
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oxidases
dehydogenases
dehydrogenases are the ones in the ETC, must be RE-OXIDIZED - heme a
- binds oxygen and is oxidized as a result
- heme c
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cov bond through cys
coordination sites taken up by his and met (why it can't bind Oxygen)