regulation of oxidative phosphorylation Flashcards
a successful OxPhos must accomplish these goals:
1.
2.
3.
- transfer electrons from NADH and FADH2 → O2
- establish a proton gradient across the inner mitochondrial membrane
- to synthesize ATP
electrons flow from molecules
with lower Eo to those with highest Eo
the difference in deltaEo is associated with
deltaGo
deltaEo and deltaGo are _______ related
inversely
deltaGo =
-nFdeltaEo
chemiosmotic hypothesis
electron transfer through the respiratory chain leads to the pumping of H+ from matrix to the innermembrane space
what 2 factors constitues a proton-motive force (pmf) to drive ATP synthesis by complex V
- pH gradient (deltapH)
- membrane potential
3 postulates of chemiosmotic theory
- the mitochondrial electron-transport chain translocates protons across the inner mitochondrial membrane as electrons flow from one respiratory electron-transport chain complex to the next
- ATP synthase uses the proton motive force (pmf) to drive the phosphorylation of ADP
- the inner mitochondrial membrane is impermeable to H+ and OH- ions. if the membrane is disrupted, a pmf cannot be established, and ATP synthesis does not occurs
ATP synthase (complex V) is located
embedded in inner membrane
Fo subunit of ATP synthase
is stick-embedded in membrane
has a proton channel
F1 subunit of ATP synthase
is ball- protudes into matrix
contains catalytic domains
F1 subunits alpha and beta are arranged alternately in a hexameric ring, both bind nucleotides but only _______ are catalytically active
beta
ATP synthase molecules associate with each other to form
dimer
ATP synthase dimers come together to form
oligomers that stabilize the individual molecules to rotational forces requried for catalysis
ATP synthase maintains _______ in inner membrane
curvature
cristae allow
the proton gradient to be in close proximity to the ATP synthase
1 mol of ATP requires
3 + 1 H+ passage [3 of which are being used in the F0 turbine (cyclothorn) to move ADP to a closer proximity to the complex]
oligomycin
disrupts proton transport through the channel
ATP and ADP are _______ across the mitochondrial membrane
not permeable
ATP-ADP translocase family
reside in the outer and innter mitochondrial membranes
works with mitochondrial carriers
flow of ADP and ATP are coupled, ADP enters matrix
only if ATP leaves
ATP-ADP translocase has recently been called
complex VI
reduced NADH cannot cross the mitochondrial membrane, it requires these shuttle systems:
- malate-aspartate shuttle
- glycerophosphate shuttle
malate-aspartate shuttle
NADH donates protons to malate which goes through outer and inner membrane shuttle and donates protons back to NADH to enter ETC
glycerophosphate shuttle
NADH donates protons to glycerol 3-P which translocates across outer membrane through its shuttle and then donates its protons to complex II (FAD)
malate-aspartate shuttle operates in what tissues
heart, liver, and kidneys
generates NADH in mitochondrial matrix
NADH enter into ETC at complex I
glycerophosphate-shuttle operates in
skeletal muscle and grain
generate FADH2 in the inner mitochondrial membrane
FADH2 joins ETC at CoQ (which is very close to complex II)
what inhibits the activity of PDH/PDC
high levels of acetyl CoA, NADH, and ATP
(high energy)
what activates PDH/PDC
high levels of ADP and pyruvate
(low energy)
regulation of cellular respiration by ADP levels is called
respiratory control or acceptor control
when transfer of electrons is inhibited:
- a decrease in the:
- a decrease in the:
- inhibition of _______ synthesis
- pumping of protons
- protein gradient
- ATP
some organisms can uncouple oxphos from ATP synthesis (by passes ATP synthesis); this is used to
generate heat and maintain body temperature (in hibernating animals)
uncoupling of oxphos from ATP synthesis happens in
brown adipose tissue
(rich in mitochondria)
(reddish brown due to cytochromes and hemoglobin)
(new-born babies)
inner mitochondrial membrane uncoupling proteins
UCP 1 (thermogenin)
(also UCP 2 and UCP 3) - play a role in energy homeostasis
UCP 1 (thermogenin)
transfers protons from intermembrane space to matrix side; this energy is converted to heat instead of ATP
how does UCP 1 work
allows protons to leak back into matrix (disrupts membrane integrity)
brown adipose tissues is revealed upon
exposure to cold temperatures
