ETC QUESTIONS AND ANSWERS
What is the ETC? - Answers- A chain of proteins in the mitochondria
What is respiratory control? - Answers- mechanism by which the concentration of ADP
in mitochondria controls the rates of oxidation and phosphorylation
What is uncoupling of oxidative phosphorylation? - Answers- the re-entrance of protons
into the mitochondrial matrix without going through ATP synthase
Give 3 examples of uncoupler compounds - Answers- 2,4-dinitrophenol, valinomycin, &
gramicidin A
Explain the mechanism behind 2,4-dinitrophenol - Answers- oxygen on 2,4-
dinitrophenol can form a hydroxyl group in the intermembrane space
the molecule, now uncharged, freely diffuses through the inner membrane
the hydrogen is released from the hydroxyl group
How does valinomycin act as an uncoupler? - Answers- dissipates the membrane
potential essential for the proton-motive force
by making the inner membrane permeable to potassium ions
Why is brown adipose tissue colored? - Answers- large number of mitochondria
What UCP is associated with brown adipose tissue? - Answers- UCP1
Describe the mechanism of nonshivering thermogenesis - Answers- cold
release of norepinephrine
increase in lipase
, oxidation of triacylgycerols
fatty acids activate UCP1
*UCP1 allows protons to pass into the matrix without passing through ATP synthase;
this allows the energy from the proton gradient dissipation to be released as heat
How does inorganic phosphate get into the inner membrane of the mitochondria? -
Answers- symport with H+
What is the ATP/ADP translocase? - Answers- antiport with 1:1 exchange of ATP
out/ADP in
Name 2 inhibitors of ATP/ADP translocase. How do they inhibit ETC? - Answers-
atractyloside (cytosolic) & bongkrekik acid (matrix). They indirectly inhibit ETC by
preventing ADP phosphorylation thus preventing depletion of the H+ ion gradient.
The mutations that cause Mitochondrial diseases affect oxidative phosphorylation &
ultimately ATP production, which body systems are most affected? - Answers- systems
that are very energy dependent, such as: the CNS, skeletal muscle, heart & kidney
What are the 4 mitochondrial diseases? - Answers- LHON, MERRF, MELAS, &
Aminoglycoside Induced Deafness
(Leber Hereditary Optic Neuropathy
Myoclonic Epilepsy & Ragged-Red Fiber
Mitochondrial myopathy, encephalomyopathy, lactic acidosis & stroke-like episodes)
Where are protons pumped into during oxidative phosphorylation? - Answers-
intermembrane space
What is the mechanism of gramicidin A? - Answers- makes the inner membrane
permeable to protons
What is the ETC? - Answers- A chain of proteins in the mitochondria
What is respiratory control? - Answers- mechanism by which the concentration of ADP
in mitochondria controls the rates of oxidation and phosphorylation
What is uncoupling of oxidative phosphorylation? - Answers- the re-entrance of protons
into the mitochondrial matrix without going through ATP synthase
Give 3 examples of uncoupler compounds - Answers- 2,4-dinitrophenol, valinomycin, &
gramicidin A
Explain the mechanism behind 2,4-dinitrophenol - Answers- oxygen on 2,4-
dinitrophenol can form a hydroxyl group in the intermembrane space
the molecule, now uncharged, freely diffuses through the inner membrane
the hydrogen is released from the hydroxyl group
How does valinomycin act as an uncoupler? - Answers- dissipates the membrane
potential essential for the proton-motive force
by making the inner membrane permeable to potassium ions
Why is brown adipose tissue colored? - Answers- large number of mitochondria
What UCP is associated with brown adipose tissue? - Answers- UCP1
Describe the mechanism of nonshivering thermogenesis - Answers- cold
release of norepinephrine
increase in lipase
, oxidation of triacylgycerols
fatty acids activate UCP1
*UCP1 allows protons to pass into the matrix without passing through ATP synthase;
this allows the energy from the proton gradient dissipation to be released as heat
How does inorganic phosphate get into the inner membrane of the mitochondria? -
Answers- symport with H+
What is the ATP/ADP translocase? - Answers- antiport with 1:1 exchange of ATP
out/ADP in
Name 2 inhibitors of ATP/ADP translocase. How do they inhibit ETC? - Answers-
atractyloside (cytosolic) & bongkrekik acid (matrix). They indirectly inhibit ETC by
preventing ADP phosphorylation thus preventing depletion of the H+ ion gradient.
The mutations that cause Mitochondrial diseases affect oxidative phosphorylation &
ultimately ATP production, which body systems are most affected? - Answers- systems
that are very energy dependent, such as: the CNS, skeletal muscle, heart & kidney
What are the 4 mitochondrial diseases? - Answers- LHON, MERRF, MELAS, &
Aminoglycoside Induced Deafness
(Leber Hereditary Optic Neuropathy
Myoclonic Epilepsy & Ragged-Red Fiber
Mitochondrial myopathy, encephalomyopathy, lactic acidosis & stroke-like episodes)
Where are protons pumped into during oxidative phosphorylation? - Answers-
intermembrane space
What is the mechanism of gramicidin A? - Answers- makes the inner membrane
permeable to protons
