Lecture 4 - Oxidative Phosphorylation and Mitochondrial Function

Question 1

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.

Answer 1

Oxidation

Question 2

Adenylate kinase catalyzes the conversion of 2 ADP to ATP and AMP. Where in the mitochondria is this enzyme found?

Answer 2

Intermembrane space

Question 3

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?

Answer 3

Creatine kinase

Question 4

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

Answer 4

E - Glutamate dehydrogenase is associated with the mitochondrial matrix.

Question 5

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

Answer 5

C. a-glycerol-P dehydrogenase is associated with the inner membrane of the mitochondria

Question 6

The function of the electron transport chain (respiratory chain) is to:

Answer 6

collect and oxidize NADH and FADH2 from various sources

Question 7

The 5 major components of the electron transport chain are the enzymes and coenzymes involved in handling electrons, including:

Answer 7

1. NAD-linked dehydrogenases
2. Flavoproteins
3. Iron-sulfur proteins
4. Coenzyme Q
5. Cytochromes

Question 8

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

Answer 8

B - electrons are passed, but not H+ is pumped by Complex II.

Question 9

The number of H+ pumped due to NADH is _______ than H+ pumped due to FADH2 entering through Complex II.

Answer 9

greater (electrons are passed, but no H+ is pumped by Complex II)

Question 10

Electrons derived from the B-oxidation of fatty acids bypass both Complex I and Complex II and are directly passed to:

Answer 10

CoQ

Question 11

Complex I of the ETC accepts electrons from ___________ and passes them along to CoQ.

Answer 11

mitochondrial NADH

Question 12

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.

Answer 12

FADH2

Question 13

Electrons are transferred from Complex III to Complex IV via _______, a mobile component of the chain.

Answer 13

cyt c

Question 14

Complex III is composed of two cytochromes. What are they?

Answer 14

1. cyt. b

2. cyt c1

Question 15

Arrangement of the components in the respiratory chain is from _______ to _______.

Answer 15

electropositive (best e- donor) to electronegative (best e- acceptor)

Question 16

The transfer of electrons from a donor to oxygen is associated with the formation of _________ and ______.

Answer 16

a proton gradient and membrane potential

Question 17

What are the 3 subunits of ATP synthase?

Answer 17

1. F1 domain
2. Fo domain
3. Stalk proteins

Question 18

What process releases the energy associated with the proton gradient that is generated by the ETC?

Answer 18

the flow of protons back through the Fo channel into the matrix

Question 19

How is P/O ratio defined?

Answer 19

The number of inorganic phosphate groups incorporated into ATP per atom of molecular oxygen consumed

Question 20

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

Answer 20

B - electrons from NADH pass through all 3 of the complexes in the electron transport chain that act as pump protons

Question 21

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

Answer 21

A - these electrons bypass Complex I

Question 22

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

Answer 22

C - this directly reduces cytochrome c, bypassing Complex I and III

Question 23

The presence of an uncoupling protein, ___________, uncouples oxidation and phosphorylation and is found in the inner mitochondrial membrane of brown fat.

Answer 23

UCP1; thermogenin

Note: this process is important in warming the blood of newborns.

Question 24

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

Answer 24

D - site-specific inhibitors block e- transfer by binding to a particular component of the ETC

Question 25

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

Answer 25

A - oligomycin prevents the return flow of protons through the Fo channel into the mitochondrial matrix

Question 26

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

Answer 26

D - this is a site-specific inhibitor that binds to Complex I of the ETC

Question 27

Uncouplers dissociate _______ from _________ by making the mitochondrial membrane abnormally permeable to protons.

Answer 27

oxidation from phosphorylation

Question 28

Since there is no transport protein for NADH, a ____________ is used to get reducing equivalents from cytosolic NADH into the mitochondria.

Answer 28

shuttle system

Question 29

The net effect of the glycerol phosphate shuttle is to use cytosolic NADH to generate mitochondrial FADH2. This shuttle is enriched in:

Answer 29

brain and fast-contracting skeletal muscle

Question 30

The net efffect of the malate shuttle is to convert cytosolic NADH to mitochondrial NADH. This shuttle is particularly enriched in:

Answer 30

liver and cardiac muscle

Question 31

You stumble into a thistle bush and are effected by atractyloside toxin. What is the effect on mitochondrial transport?

Answer 31

Atractyloside inhibits the ATp-ADP exchange protein, an antiporter that exchanges mitochondrial ATP for cytosolic ADP.

Question 32

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

Answer 32

B

Question 33

What shuttle system is used to transport fatty acids from the cytosol into the mitochondrial matrix for B-oxidation?

Answer 33

Carnitine shuttle

Question 34

What shuttle is used to transport acetyl-CoA out of the mitochondria into the cytosol (e.g. for fatty acid synthesis)?

Answer 34

Citrate shuttle