Oxidative phosphorylation II Flashcards
(80 cards)
1
Q
Protons are pumped across what membrane as they flow through the Respiratory chain
A
the inner mitochondrial membrane
2
Q
What is the chemiosmotic hypothesis
A
- Purposed by Peter Mitchell in 1961
- ETC is accompanied by transport of protons from matrix to cytoplasmic side of inner membrane
- This generates a pH gradient and membrane potential
- Constitutes a proton motive force
- composed of two comments:
- chemical gradient (pH gradient)
- charge gradient - used to dive ATP synthesis (via ATP synthase)
- composed of two comments:
3
Q
what was used to supply evidence for the chemiosmotic hypothesis
A
- Synthetic phospholipid vesicles containing Bacteriorhodopsin and mitochondrial ATP synthase purified form beef heart were created
- purified ATP synthase and bacteriorhodopsin reconstituted into the vesicles (bacteriorhodopsin pumps protons when illuminated)
- Incubated with ADP+Pi
- Exposed to light and ATP generated
- — experiment clearly showed that the respiratory chain and ATP synthase are biochemically separate systems, linked only by a proton-motive force
4
Q
The F0 unit of the ATP synthase is located
A
embedded in the inner mitochondrial membrane
5
Q
The F1 unit of ATP synthase is located
A
protrudes into the mitochondrial matrix
6
Q
The F1 subunit of ATP synthase consists of ____ types of polypeptide chains
A
5 (alpha3, beta3, gamma, delta, and epsilon)
7
Q
The alpha and beta components of subunit F1 in ATP synthase are arranged alternately in a
A
hexameric ring
8
Q
Which of the ATP synthase subunits contain catalytic domains
A
F1
9
Q
What is complex V of the ETC
A
ATP synthase
10
Q
ATP synthase is a ____ and ____ structure
A
ball and stick
11
Q
What is the stick component of the ATP synthase
A
F0
12
Q
what is the ball component of the ATP synthase
A
F1
13
Q
Which of the subunits in ATP synthase have proton channels
A
F0
14
Q
does Isolated F1 subunit displays ATPase activity
A
Yes
15
Q
Both Alpha and Beta on F1 bind nucleotides but only the ____ are catalytically active
A
Beta
16
Q
Above the alpha and beta is a stalk made of ____ and ____ proteins
A
gamma and epsilon
17
Q
The gamma subunit has a long helical coil that extends into the
A
center of the alpha3 and beta3 hexamer
18
Q
What breaks the symmetry of the beta3alpha hexamer: each of the Beta subunits is distinct by virtue of its interaction with a different face of the _____
A
The gamma subunit, gamma subunit
19
Q
The F0 has a proton channel complex. This channel consists of a ring comprising from ____ c subunits that are embedded in the matrix
A
8-14 c subunits
20
Q
F0 and F1 are subunits of ATP synthase are connected by what two ways
A
- by the central gamma/epsilon stalk
- by an exterior column consists of one alpha subunit, two beta subunits, and the delta subunit
21
Q
ATP synthase molecules associate with each other to form
A
dimers
22
Q
ATP synthase dimers come together to form
A
oligomers
23
Q
What is the purpose of ATP synthase molecules associating with one another to form dimers and then oligomers
A
- association stabilizes the individual enzymes to the rotational forces required for catalysis and facilitates the curvature of the inner mitochondrial membrane
- maintains curvature in inner membrane
24
Q
The ATP synthases are located
A
at the tips of the crust, thereby enhancing the efficiency of ATP synthesis
25
-Cristae allow the proton gradient to be in ____ proximity to the ATP synthase
close
26
What is the role of the proton gradient in ATP synthase
ATP can be formed in the absence of proton gradient but it can't leave the catalytic site unless protons flow through the enzyme. Thus the role of the proton gradient is not to form ATP but to release it form the synthase
27
ATP synthase when incubated with ADP and Pi forms
ATP in the absence of the proton gradient
28
How many active sites are there on the ATP synthase
3 (the beta3 units of the F1 subunit)
29
What is the moving unit of the ATP synthase
The moving unit, or rotor, consists of the c ring and the gamma epsilon stalk
30
The three beta subunits can each perform three sequential steps in the synthesis of ATP by
Changing conformations
31
What are the three sequential steps in ATP synthesis
1. ) ADP and Pi binding
2. ) ATP synthesis
3. ) ATP release
32
What is the O conformation in the beta subunit
it is the open conformation. This allows for the release of ATP and for ADP and Pi to enter the subunit
33
What is the L conformation in the beta subunit
Loose, Has a strong binding affinity for ADP and Pi thus locking them in the subunit
34
What is the T conformation in the beta subunit
Tight, has a strong affinity for the ATP and actually drives ADP and Pi together to form ATP
35
How much does the gamma subunit rotate to move conformation states in the beta subunits
counterclockwise 120 degrees
36
each beta subunit progresses from ___ to ___ to ___ conformation
T,O,L
37
Are any two beta subunits ever in the same conformation state
No
38
What powers the rotation of the c ring on ATP synthase F0 subunit
The movement of protons through the half channels from the high proton concentration of the cytoplasm to the low proton concentration of the matrix powers the rotation of the c ring.
39
The c subunit of ATP synthase is composed of
- 2 alpha helices that span the membrane.
- Aspartic acid (glutamic acid) residue in one of the helices lies on the center of the membrane (these bind to the protons)
40
how many a subunits bind to the outside of the ring (8-14 c subunits)
a single a subunit
41
When glutamate is in a high proton environment it will ____
bind the proton
42
if glutamate is charged (unprotonated) the c subunit will
not move into the membrane
43
Does the a unit rotate with the c ring
no
44
The a subunit is composed of
2 half channels, that allow protons to enter and pass partway but not completely
45
The alpha and beta subunits of ATP synthase are members of the ______ family of proteins
P-loop NTPase family
46
Is the regeneration of NAD+ for use in glycolysis one function of the ETC
Yes
47
The major function of oxidative phosphorylation is to generate
ATP from ADP
48
Do ATP and ADP readily move across the inner mitochondrial membrane into the cytoplasm
No (ATP-ADP translocase is used)
49
What enables ATP and ADP to transverse the permeability barrier (inner mitochondrial membrane)
ATP-ADP translocase
50
Mechanism of mitochondrial ATP-ADP translocase
- Catalyzes the coupled entry of ADP into the matrix and the exit of ATP from it
- The binding of ADP form the cytoplasm favors eversion of the transporter to release ADP into the matrix.
- Subsequent binding of ATP from the matrix to the everted from favors eversion back to the original conformation, releasing ATP into the cytoplasm
51
The flow of ATP and ADP are
coupled, ADP enters the mitochondrial matrix only if ATP exits, and vice versa.
52
ATP-ADP translocase is what kind of transporter
antiporter
53
Inhibition of translocase leads to
the subsequent inhibition of cellular respiration
54
about a quarter of the proton-motive force generated by the respiratory chain is consumed by
ATP-ADP translocase's exchange process
55
The regulation of cellular respiration is governed primarily by the need for
ATP
56
The complete oxidation of glucose yields about ____ molecules of ATP
30
57
glucose is completely oxidized to
CO2
58
Regulation of cellular respiration
- levels of ATP regulate respiration
- electrons flow through ETC only when ADP phosphorylated to ATP
- Regulation by ADP levels called respiratory control
59
The regulation of the rate of oxidative phosphorylation by the ADP level is called
respiratory control or acceptor control
60
electrons are transferred to O2 only if ADP is
concomitantly phosphorylated to ATP
61
Regulation of ATP synthase
- inhibitory factor I (IF1) -inhibits hydrolytic activity of ATP synthase
- prevents the reverse reaction, i.e. ATP breakdown
- is useful to prevent the hydrolysis of ATP when oxygen not available to make protein gradient
62
Warburg effect
- the switch form oxidative phosphorylation to aerobic glycolysis as the principle means for ATP synthesis
- caused by the over-expression of IF1 (inhibitory factor 1), which is common in many types of cancers
63
Some organisms can uncouple oxphos from ATP synthesis. Why?
Used to generate heat and maintain body temperature (important in hibernating animals)
64
in animals the uncoupling of oxidative phosphorylation from ATP synthesis to generate heat is found in
brown adipose tissue (BAT)
65
why is brown adipose tissue reddish brown
due to cytochromes in the numerous mitochondria and hemoglobin present in extensive blood supply
66
Brown adipose tissue is rich in
mitochondria
67
The inner mitochondrial membrane of brown adipose tissue mitochondria contain large amounts of
uncoupling protein (UCP-1) or thermogenin
68
what is the function of uncoupling protein 1 (thermogenin)
Transfers protons form cytoplasm to matrix side without producing ATP, thus converting engr. to heat instead of ATP
69
what are the two other uncoupling proteins
UCP-2 (found in a variety of tissues)
UCP-3 (found in skeletal muscle and brown fate)
-may play a role in homeostasis
70
The family of uncoupling proteins may play a role in
homeostasis
71
_____ inhibits ATP synthase by preventing the influx of protons by binding to the carboxylate group of the c subunits required for proton binding
Oligomycin (Antibiotic and anti fungal agent)
72
Uncouples electron transport from ATP synthase
2,4-dinitrophenol (dissipates the proton gradient)
73
____ and ____ inhibit ATP-ADP translocate thus inhibiting ATP export
Atractyloside and bongkrekic acid
74
How does Oligomycin inhibit Oxidative phosphorylation
Inhibits ATP synthase by preventing the influx of protons through ATP synthase by bidding to the carboxylate group of the c subunits
75
How does 2,4 dinitrophenol inhibit oxidative phosphorylation
uncouples electron transport from ATP synthase
In the presence of 2,4 dinitrophenol (DNP) electron transport from NADH to O2 proceeds in a normal fashion, but ATP is not formed by mitochondrial ATP synthase, because the proton-motive force across the inner mitochondrial membrane is continuously dissipated.
- Leads to increase in oxygen consumption and release of Heat
76
Inhibit electron transfer in NADH-Q oxidoreductase
Rotenone and Amytal
77
Inhibits the electron flow form cytochrome bH in Q-cytochrome c oxidoreductase
Antimycin A
78
Cyanide (CN-), Azide (N3-), and Carbon monoxide (CO) inhibit
Cytochrome c Oxidase
| cyanide and Azide react with the ferric form of heme a3 and carbon monoxide inhibits the ferrous form
79
what inhibits cytochrome c oxidase
Cyanide, Axide, and carbon monoxide
80
Atractyloside and Bonkrekic inhibit
ATP export by inhibiting ATP-ADP translocase
