MCQs Flashcards
Which type of bond makes acetyl CoA an energy carrier molecule?
thioester
The standard free energy change for the following reaction
malate + NAD+ → oxaloacetate + NADH + H+
was calculated in the lecture as ΔG°’ = + 28 kJ/mol, yet the reaction proceeds in this direction in the TCA cycle, because oxaloacetate is rapidly removed by conversion to
citrate
The equation that relates E°’ to the equilibrium constant for a reaction was not provided in the lecture, but you can work out that it is:
ΔEo’ = RT ln Keq
————-
nF
what does NADH released when oxidised
2 electrons and 1 proton
between complex I and complex II:
only one is an enzyme in the TCA cycle. True or false?
True
Complex II is succinate dehydrogenase and links TCA to ETC
between complex I and complex II: true or false?
both feed electrons into different rounds of the Q cycle
False
QH2 from I and II are functionally equivalent and so Complex III cannot distinguish between them
between complex I and complex II: true or false?
only one complex pumps protons across the IMM
true
I does
II doesn’t
between complex I and complex II: true or false?
One reduces FADH2 and the other NADH
True
I reduces NADH
II reduces FADH2
What is the fate of semi-quinone form of ubiquinone produced during round 1 of Q cycle?
It is fully reduced to GH2
symbol for semi quinone and when is it produced
Q-
produced during round one of Q cycle
where is the F1 subunit of ATPsynthase located
matrix
where is cytochrome C located in mitochondria
IMS
where is Complex II located
matrix
True or false:
The complex reducing FADH2 sometimes gains enough energy from that reaction to pump protons across the IMM.
False
redox potential of FADH2 oxidation never provides enough energy to pump protons
True or false:
The complex reducing NADH always gains enough energy from that reaction to pump protons across the IMM.
FALSE –
while redox potential of NADH oxidation can provide enough energy to pump protons, once the proton gradient is large enough, the ΔG of NADH oxidation is insufficient to pump protons
True or false:
ComplexesI, III and IV all pump protons through a transmembrane protein complex
FALSE –
Complex III uses the Q cycle rather than pumping protons through the complex.
True or false:
In addition to pumping protons directly across the membrane, complex IV also removes protons from the matrix
True:
2 protons are removed from the matrix and combined with O2 and electrons to produce water
what is the site of O2 reduction in mitochondria
Complex IV
formation of water
In the absence of oxygen, cells can still produce small amounts of ATP through substrate-level phosphorylation during glycolysis. Why must lactate be produced to allow this process to continue
To oxidise NADH
Cells can run glycolysis in the absence of O2, but soon run out of NAD+ which is required for glycolsysis.
Conversion of pyruvate to lactate oxidises NADH to NAD+ allowing glycolysis to continue
what is required for the F0 domain of ATP synthase to rotate
- proton gradient
- Pi
- ADP
is NADH required for the F0 domain of ATP synthase to rotate
nope
why can’t the F0 domain of ATP synthase to rotate without ADP
Because this allows respiration to be regulated by ADP/ATP ratio – ie cellular energy status
True or false:
Mutations in the mitochondrial genome affect all the mitochondria in a cell
false
Proportion of mutant and normal DNA vary between mitochondria meaning some mitochondria or some tissues may be unaffected by the mutation
Dynamin-related protein 1 (Drp1) is involved in which process
mitochondrial fission:
- Cytosolic Dynamin-related protein (Drp)1 is phosphorylated
- Drp1 recruited to mitochondria and binds receptors
- Forms cuff around mitochondrion which constricts the organelle
- Constriction severs both membranes
- Generates new mitochondria
effect of TTFA on ETC
binds at quinone reduction site of Complex II, preventing formation of ubiquinone
- use of succinate as fuel will be low, bc Complex II is where TCA joins ETC
- use of pyruvate high
effect of rotenone on ETC
Complex I
- inhibits transfer of electrons from Fe-S in Complex I to ubiquinone
- this interferes with NADH
- use of pyruvate as fuel low
- use of succinate as fuel high
effect of antimycin on ETC
Complex III
- binds to Qi, inhibiting oxidation of ubiquinone
- disrupted Q-cycle
effect of cyanide of ETC
complex IV
- binds to Fe atoms and inhibits transfer of electrons to oxygen
prevents cells from reducing oxygen to water
effect of oligomycin on ETF
an antibiotic
- inhibits ATP synthase
- blocks proton channel of F0 subunit
- stops ETC
is DNP weak or strong acid
weak
HA H+ + A-
which tissue expresses large amounts of UCP-1
brown adipose tissue
why does brown adipose tissue express lots of UCP-1
allows for controlled uncoupling of mitochondria to produce heat
example of another mitochondrial uncoupler
DNP
it is a weak acid and is membrane impermeable
what do beta islets produce
insulin
what do alpha islets produce
glucagon
what do delta islets produce
somatostatin
what secondary hormone does insulin induce
PIP3
what secondary hormone does glucagon induce
cAMP
what secondary hormone does adrenaline induce
cAMP
what are the main substances, from other tissues, that are used by the liver for gluconeogenesis
lactate
alanine
glycerol
how is the rate of kexokinase active affects across physiological blood glucose levels?
(Km = 0.1mM)
it will not significantly change during physiological ranges
if glucokinase has a Km of 10mM, will it saturated at 20mM
NO
how does GLUT2 compare to GLUT4 in terms of affinity
GLUT2 has lower affinity than GLUT4
what directly triggers insulin vesicles to fuse with plasma membrane and release insulin?
increased intracellular Ca2+ concentration
is glycogen transported from muscle to liver
nope
