oxidative phosphorylation Flashcards
describe the chemiosmotic hypothesis
energy input for ATP synthesis comes from proton gradient established by the movement of electrons along the electron transport chain
how are protons moved in the electron transport chain?
H+ are moved from the matrix into the inner membrane space, making the inner membrane space more acidic
what is required for the chemiosmotic hypothesis to be true?
inner mitochondrial membrane must be impermeable to H+
complex I
NADH dehydrogenase
accepts e- from NADH, hands off to CoQ
Complex II
succinate dehydrogenase
accepts e- from FADH2, hands off to CoQ
complex III
cytochrome b-c1
accepts e- from CoQ, hands off to cytochrome c
complex IV
cytochrome oxidase
accepts e- from cytochome C, uses E- to convert O2 –> H20
complex V
ATP synthase, uses H+ gradient to form ATP
most of the complexes are a mix of mito and nuclear DNA, what is the exception?
complex II is only nuclear DNA (also smallest with only 4 subunits)
diseases assoc with complex I and complex IV
both assoc with genetic disease and also seen in neurologic diseases
disease assoc with complex II
genetic d/o and paraganglioma
disease assoc with complex V
cancer
which complexes have iron-sulfur centers?
I, II, III
structure of iron-sulfur centers
iron atoms complexed with sulfur from cysteine, responsible for maintaining correct protein structure
what is one reason for fatigue in iron deficiency?
if iron is deficient, then iron-sulfur centers will be decreased, leading to improper configuration of iron-sulfur centers = effects on complexes I, II, III = decreased ATP production
MOA of doxorubicin
inhibits Coenzyme Q thereby inhibiting flow of electrons in the ETC and inhibiting ATP production
2 undesired effects of doxirubicin
cardiotoxic (binds cardiolipin)
forms free radicals that may damage mito membrane
describe Reye’s syndrome
occurs with aspirin use during viral infection, causes mitochondria to rupture leading to decreased ATP synthesis and also decreased ability to form urea = NH4+ levels accumulate and hepatic coma results, more pronounced effect in children
what controls flux through the ETC?
energy charge of the cell (ATP/ADP), increased ADP will increase flux through ETC
describe using respirometer to measure mitochondrial efficiency
use respirometer to measure O2, should see that O2 consumption increases when ADP added if mito are working properly
how many H+ will be pumped per NADH
10 4 @ I 4 @ III 2 @ IV = 2.5 ATP/NADH
how many H+ will be pumped per FADH2
6
4 @ III
2 @ IV
= 1.5 ATP/FADH2
what are “chemical uncouplers”?
substances that disrupt the H+ gradient in the mitochondria by allowing H+ to pass into matrix by other means and NOT by ATP synthase
4 examples of chemical uncouplers
2,4-dinitrophenol
FCCP
CCCP
aspirin/salicylate
describe effects of uncoupling by salicylate
“partial” uncoupler at high concentrations
due to uncoupling, ATP will decrease and AMP will increase = increased glycolysis by stimulation of phosphofructokinase = increased lactate and lactic acidosis
what is the “uncoupler” found in brown fat?
thermogenin
what is the function of brown fat?
heat generation/thermoregulation in infants- when norepinephrine stimulates fat lipolysis, thermogenin allows brown fat cells to generate heat
uncoupling effects of thyroid hormone
thyroid hormone is a partial uncoupler = pts with hyperthyroidism will feel hot, also will not be able to derive max energy via oxphos
what is “ANT”?
ATP-ADP antiporter in the mito inner membrane, exports newly synthesized ATP and imports ADP
what is the importance of creatine phosphate?
synthesized by creatine kinase, it is a stored form of energy present in the inner membrane space in muscle mitochondria, the phosphate can be quickly transferred to ADP to make ATP
how is the mitochondrial permeability transition pore formed?
ANT associates with VDAC
what are the consequences of MPTP formation?
allows mito membrane to be more permeable, can result in cell swelling and apoptosis
why are “shuttles” needed?
to move the NADH that was synthesized during glycolysis into the mitochondria so that it can be used in the ETC
where is the glycerol-phosphate shuttle? MOA?
found in skeletal mm and brain
NADH in cytosol gives e- to FADH2
= 1.5 ATP per NADH
where is the malate-aspartate shuttle? MOA?
found in liver, kidney, heart
NADH in cytosol gives e- to oxaloacetate forming malate
malate travels into mitochondria and gives e- to NAD+ to yield NADH and reform oxaloacetate
=2.5 ATP per NADH
why is the rho zero cell system used?
in a person with mito disease, use this to determine if the problem is coming from nuclear DNA or mito DNA contributions
how does rho zero system work?
-pts cell is enucleated, only mito remain
- rho zero cell has mito killed off
cells are joined to make cybrid
if mito function in cybrid is abnormal, then pts mito are abnormal
what is the effect of statins on ETC?
statins will decrease Coenzyme Q-10
