MCT Block 3 Exam
The goal of the PDHc-catalyzed reaction is to turn ____________ into ____________.
To do this, it requires 5 other things: ____________, _____________, ____________,
____________, and __________. correct answers pyruvate; acetyl-CoA and NADH;
TPP (thiamine, a.k.a. Vitamin B1); lipoic acid; CoASH; FAD; NAD+ (tender loving care
for Nancy);
The E1 component of PDH catalyzes the conversion of ________________ into
hydroxyethyl-TPP. The E2 component catalyzes its conversion into _____________ via
lipolysine as a intermediate aceyl carrier, leaving a reduced lipolysine. The E3 complex
then uses ________ to re-oxidize the lipolysine, and then it also uses __________ to
re-oxidize the __________ back to ___________, producing ______________. correct
answers pyruvate; acetyl-CoA; FAD; NAD+; FADH2; FAD; NADH
PDH is mainly activated by _______________ via the ______________ enzyme, as
well as by ____________ in adipocytes and ____________ in cardiac muscle.
PDH is mainly inhibited by _______________ via the ______________ enzyme, as well
as by an excess of __________ or ___________. correct answers dephosphorylation;
PDH phosphatase; insulin; catecholamines; phosphorylation; PDH kinase; acetyl-CoA;
NADH
PDH phosphatase is _______________ by calcium and magnesium. Presence of
calcium and magnesium would therefore _________ the action of PDH itself.
PDH kinase is _______________ by calcium among other things, and is __________
by NADH, ATP, and acetyl-CoA. Presence of calcium would therefore _________ the
action of PDH itself, while presence of NADH would ___________ the action of PDH
itself. correct answers activated; activate; inhibited; activated; activate; inhibit
_____________________ manifests within the 1st year, showing signs of severe
metabolic acidosis, microcephaly, lethargy, hypotonia, and seizures. It is an X-linked
recessive defect in PDH, but the __________ gene is always inactivated in females for
some reason, resulting in roughly __________ manifestation between males/females.
correct answers X-linked Leigh syndrome; wild type; equal
This element is highly toxic because it inhibits dehydrogenases such as PDH, resulting
in hypoglycemia. Additionally, its pentavalent form replaces _____________. correct
answers arsenic; phosphate
The TCA cycle has no direct hormonal regulation. Instead, its rate limiting step -
catalyzed by ________________ - is inhibited by ____________ and ____________
,which indicate that we have plenty of energy. Malate DH and 2-oxoglutarate (α-
ketoglutarate) DH also make ____________ and are inhibited by it.
It requires ____________ for the reactions catalyzed by PDH and OGDH.
___________ and _________ are enzymes in the TCA cycle that are also tumor
suppressor genes. correct answers IDH (isocitrate dehydrogenase); ATP; NADH;
NADH; thiamine; fumarase; IDH (isocitrate dehydrogenase);
Some important intermediates in the TCA cycle:
___________ which is important for AA synthesis.
___________ which is important for gluconeogenesis
___________ which is important for heme synthesis correct answers OAA; malate;
succinyl-CoA
Overall, the TCA cycle makes 1 _______, 1 ______3 _______, and 2 _______. It does
this _______ per glucose molecule. correct answers GTP; FADH2; NADH; CO2; twice
The _________ membrane of mitochondria is essentially impermeable, requiring lots of
transporter. The _________ membrane has lots of porins which allow essentially free
passage.
One very important antiporter is for ________ and ________, the second of which is a
regulator of respiration. correct answers inner; outer; ATP, ADP
While mitochondrial diseases are inherited almost exclusively maternally, many
mitochondrial problems have to do with nuclear DNA. Why? correct answers mtDNA
encodes 13 proteins, 2 rRNAs, and 22tRNAs, but mitochondria require over 900
proteins
The ETC is most easily inhibited at complex ______. A very potent inhibiter of this
complex is ___________ which binds tightly to ferric iron. Inhibition of this complex
stops reduction of ____________ and will shut down the ETC by backing it up.
This poisoning can be reversed by administering hydroxocobalmin which steals the
inhibitor or by nithiodote which makes more _____________ which will steal it as well.
Olygomycin inhibits _____________, which causes the ETC to keep consuming oxygen
even though it can't make ATP. correct answers IV; cyanide; oxygen; methemoglobin;
ATP synthase
NADH doesn't directly enter the mitochondria. Instead it "enters" via the __________
shuttle for NADH on the inside or the ___________ shuttle for FADH2 on the inside.
In the mitochondria, NADH gives its electrons to complex ____, NADH DH. This
complex transfers the electrons to CoQ and pumps _____ protons per electron.
, FADH2 gives its electrons to complex ____, succinate-ubiquinone oxidoreductase. This
complex transfers the electrons to CoQ and pumps _____ protons per electron.
CoQ brings the electrons to complex ____, CoQ-cytochrome reductase and pumps
____ protons per electron.
Complex ____ hands 4 electrons from cytochrome c to oxygen and turns it into water
while pumping ____ protons TOTAL.
ATP synthase (complex V) requires ____ protons for one full rotation, during which time
it produces ____ ATP.
All this means that (theoretically) each NADH contributes to ____ ATP, while each
FADH2 contributes to ____ ATP. correct answers malate-aspartate; glycerol
phosphate; I; 2; II; 0; III; 2; IV; 4; 8; 3; 3.75; 2.25
Why do mitochondrial diseases tend to predominantly affect the brain and muscle? Why
do they often cause lactic acidosis? correct answers They use a lot of ATP; when ETC
doesn't work, pyruvate is reduced to lactate to regenerate NAD+
Brown fat expresses _______________ which naturally uncouples the inner
mitochondrial membrane to dissipate the gradient and make heat. ______ can also
cause this (unnaturally) because it can easily bus protons back and forth across
membranes. correct answers UCPs (uncoupling proteins); DNP (2,4-dinitrophenol
Thiamine (B1)
Active form: _______ generated by thiamine diphosphotransferase
Involved in oxidative decarboxylation of ___________.
Major enzymes are _________ (pyruvate to acetyl-CoA and NADH), ____________
(TCA cycle), and ___________ (α-ketoacid DH, Maple syrup urine disease).
The easiest way to test for a thiamine deficiency is with a _____________ assay,
because it requires thiamine as a cofactor. correct answers TPP; α-ketoacids; PDHc; α-
ketoglutarate DH (2-OGDH); BCKD; transketolase
Dietary __________ deficiency is referred to as ____________. The _________ form is
EtOH-mediated (impairs uptake), the _________ form results from chronic deficiency
(poor eating habits) and results in progressive enlargement of all four heart chambers
called _________.
Deficiency leads to ______________ due to PDHc inhibition, which is further
exacerbated by EtOH consumption. Other symptoms include constipation, appetite
suppression, nausea, peripheral neuropathy, vertical nystagmus, organic toxic
psychosis, mental depression, fatigue, cardiovascular and muscular defects.
The neurological condition due to thiamine deficiency associated with EtOH abuse is
termed _________________. A chronic deficiency results in learning a memory deficits
and the onset of psychosis, and is termed ______________. They can also appear
