Lecture 4 - Oxidative Phosphorylation and Mitochondrial Function Flashcards
Most of the energy derived from food originates in electron pairs that are found in chemical bonds. ___________ reactions result in the loss of the electrons from cellular metabolites with the concomitant release of energy that is trapped ultimately in the form of ATP.
Oxidation
Adenylate kinase catalyzes the conversion of 2 ADP to ATP and AMP. Where in the mitochondria is this enzyme found?
Intermembrane space
One particular enzyme that is found in the mitochondrion intermembrane space catalyzes the conversion of Creatine + ATP to Creatine-P + ADP. What enzyme is being described?
Creatine kinase
Which enzyme is NOT associated with the inner membrane of the mitochondria?
A. Succinate dehydrogenase B. Adenine nucleotide translocase C. Pi transporter D. Respiratory chain proteins E. Glutamate dehydrogenase F. ATP synthetase
E - Glutamate dehydrogenase is associated with the mitochondrial matrix.
Which enzyme is NOT associated with the mitochondrial matrix?
A. Enzymes of the TCA cycle
B. Enzymes for B-oxidation of fatty acids
C. a-glycerol-P dehydrogenase
D. Pyruvate dehydrogenase complex
E. Branched chain amino acid dehydrogenase complex
C. a-glycerol-P dehydrogenase is associated with the inner membrane of the mitochondria
The function of the electron transport chain (respiratory chain) is to:
collect and oxidize NADH and FADH2 from various sources
The 5 major components of the electron transport chain are the enzymes and coenzymes involved in handling electrons, including:
- NAD-linked dehydrogenases
- Flavoproteins
- Iron-sulfur proteins
- Coenzyme Q
- Cytochromes
Which multienzyme complex of the ETC does NOT pump H+ out of the matrix?
A. Complex I
B. Complex II
C. Complex III
D. Complex IV
B - electrons are passed, but not H+ is pumped by Complex II.
The number of H+ pumped due to NADH is _______ than H+ pumped due to FADH2 entering through Complex II.
greater (electrons are passed, but no H+ is pumped by Complex II)
Electrons derived from the B-oxidation of fatty acids bypass both Complex I and Complex II and are directly passed to:
CoQ
Complex I of the ETC accepts electrons from ___________ and passes them along to CoQ.
mitochondrial NADH
Complex II is the same as the succinate dehydrogenase of the TCA cycle. It passes electrons from succinate through _______ and an iron-sulfur center to CoQ.
FADH2
Electrons are transferred from Complex III to Complex IV via _______, a mobile component of the chain.
cyt c
Complex III is composed of two cytochromes. What are they?
- cyt. b
2. cyt c1
Arrangement of the components in the respiratory chain is from _______ to _______.
electropositive (best e- donor) to electronegative (best e- acceptor)
The transfer of electrons from a donor to oxygen is associated with the formation of _________ and ______.
a proton gradient and membrane potential
What are the 3 subunits of ATP synthase?
- F1 domain
- Fo domain
- Stalk proteins
What process releases the energy associated with the proton gradient that is generated by the ETC?
the flow of protons back through the Fo channel into the matrix
How is P/O ratio defined?
The number of inorganic phosphate groups incorporated into ATP per atom of molecular oxygen consumed
Oxidation of ____________ substrates have a P/O ratio of 2.5.
A. FAD-linked
B. NAD-linked
C. Reduced ascorbate
D. None of these are correct
B - electrons from NADH pass through all 3 of the complexes in the electron transport chain that act as pump protons
Oxidation of ____________ substrates have a P/O rationof 1.5.
A. FAD-linked
B. NAD-linked
C. Reduced ascorbate
D. None of these are correct
A - these electrons bypass Complex I
Oxidation of ____________ substrates have a P/O ratio of 1.
A. FAD-linked
B. NAD-linked
C. Reduced ascorbate
D. None of these are correct
C - this directly reduces cytochrome c, bypassing Complex I and III
The presence of an uncoupling protein, ___________, uncouples oxidation and phosphorylation and is found in the inner mitochondrial membrane of brown fat.
UCP1; thermogenin
Note: this process is important in warming the blood of newborns.
Azide, carbon monoxide, and cyanide are classified as site-specific inhibitors of ATP synthesis because they:
A. directly block phosphorylation at the Fo channel
B. bind to Complex I in the ETC
C. make the mitochondrial membrane abnormally permeable to protons, dissociating oxidation from phosphorylation
D. bind to Complex IV in the ETC
D - site-specific inhibitors block e- transfer by binding to a particular component of the ETC
Oligomycin is classified as an inhibitor of Complex V (ATP Synthase) because it:
A. directly block phosphorylation at the Fo channel
B. bind to Complex I in the ETC
C. make the mitochondrial membrane abnormally permeable to protons, dissociating oxidation from phosphorylation
D. bind to Complex IV in the ETC
A - oligomycin prevents the return flow of protons through the Fo channel into the mitochondrial matrix
Which of the following is NOT classified as an “uncoupler” inhibitor of mitochondrial ATP synthesis?
A. Ionophores B. Uncoupling proteins C. Dinitrophenol D. Amytal E. Very high thyroid hormone
D - this is a site-specific inhibitor that binds to Complex I of the ETC
Uncouplers dissociate _______ from _________ by making the mitochondrial membrane abnormally permeable to protons.
oxidation from phosphorylation
Since there is no transport protein for NADH, a ____________ is used to get reducing equivalents from cytosolic NADH into the mitochondria.
shuttle system
The net effect of the glycerol phosphate shuttle is to use cytosolic NADH to generate mitochondrial FADH2. This shuttle is enriched in:
brain and fast-contracting skeletal muscle
The net efffect of the malate shuttle is to convert cytosolic NADH to mitochondrial NADH. This shuttle is particularly enriched in:
liver and cardiac muscle
You stumble into a thistle bush and are effected by atractyloside toxin. What is the effect on mitochondrial transport?
Atractyloside inhibits the ATp-ADP exchange protein, an antiporter that exchanges mitochondrial ATP for cytosolic ADP.
Which of the following transport proteins found in the inner mitochondrial membrane can act either as an antiporter or as a symporter?
A. ATP-ADP exchange protein
B. Phosphate transport protein
C. Pyruvate transporter
D. All of the above
B
What shuttle system is used to transport fatty acids from the cytosol into the mitochondrial matrix for B-oxidation?
Carnitine shuttle
What shuttle is used to transport acetyl-CoA out of the mitochondria into the cytosol (e.g. for fatty acid synthesis)?
Citrate shuttle
