Biochemistry Ch. 19 – Photophosphorylation

Front 1

Photophosphorylation differs from oxidative phosphorylation in that the former requires the input of energy in the form of ___________ to create a good electron donor. In photophosphorylation, electrons flow through a series of membrane-bound carriers including ___________ , ___________ , and ___________ proteins, whereas ___________ are pumped across a membrane to create an ___________ potential.

Back 1

Light


cytochromes, quinones, iron-sulfur, protons, electrochemical.

Front 2

Describe the effect(s) that a mitochondrial uncoupler such as 2,4-dinitrophenol (DNP) would have on photophosphorylation.

Back 2

Uncouplers like DNP, which act by dissipating transmembrane proton gradients, would uncouple photophosphorylation because it is also dependent on a transmembrane proton gradient to provide the energy required to synthesize ATP from ADP and Pi.

Front 3

Discuss how “accessory pigments” are able to extend the range of light absorption of the chlorophylls. Name some accessory pigments.

Back 3

Accessory pigments are able to absorb light and transfer the absorbed energy to the chlorophylls in a process know as “exciton transfer.” Two accessory pigments are β-carotene and lutein.

Front 4

What is an action spectrum, and what do peaks in an action spectrum signify? Show a typical action spectrum plot for photosynthesis.

Back 4

An action spectrum is a plot of the effectiveness of a process (such as photosynthesis) versus wavelength of incident light. Its peaks signify the presence of a chromophore that absorbs light at that wavelength.

Front 5

Describe what happens at photosystem I from the point where an antenna chlorophyll molecule absorbs a photon of light to the passage of an electron to NADP+.

Back 5

The antenna chlorophyll molecule passes the energy of the photon, via exciton transfer, to neighboring chlorophyll molecules and ultimately to reaction center chlorophyll molecules. This excites P700 to P700*, which donates an electron to A0. From A0, electrons pass to phylloquinone (A1), through an Fe-S protein, to ferredoxin, then through a flavoprotein to NADP+.
P700* → A0 → A1 → Fe-S → NADP+ (See Figs. 19-43, p. 698, and 19-46, p. 703.)

Front 6

Give five general classes of electron carriers that function in both mitochondrial electron transfer to O2 and photosynthetic electron transfer.

Back 6

Any five of the following: pyridine nucleotides (NADH, NADPH); flavin nucleotides (FADH2, FMNH2); quinones (ubiquinone, plastoquinone); cytochromes; Fe-S proteins; flavoproteins.

Front 7

The processes of oxidative phosphorylation coupled with electron transfer (in mitochondria) and photophosphorylation (in chloroplasts) resemble each other in certain respects. Describe five ways in which the two processes are similar, and describe three significant differences between the two processes.

Back 7

Similarities include:
both contain a chain of membrane-bound electron carriers;

electron transfer leads to establishment of a proton gradient;

an ATPase/ATP synthase is a coupling factor;

ATP synthesis is sensitive to uncouplers;

both require a system of intact membranes to separate electrons inside and outside.

Differences include:

source of reducing power (NADH vs. light),

product (ATP in respiration; NADPH and/or ATP in photosynthesis);

source of oxidizing power (O2 in mitochondria; light in photosynthesis).

Front 8

Show the path of electrons from photosystem II to NADPH in the chloroplast. What is the source of the energy that moves electrons through this path? Show where oxygen is involved in this pathway.

Back 8

H2O → P680 → Pheophytin → PQA → PQB → cyt b6f complex → Plastocyanin → P700 → A0 → A1 → Fe-S → Ferredoxin → Ferredoxin-NADP+ oxidoreductase → NADP+.
The energy that drives the electron flow is from light. O2 is generated from H2O when H2O donates electrons to PSII.

O2 is generated by the splitting and oxidation of H2O, driven by the absorption of a photon by PSII (which occurs only in daylight). (See Fig. 19-49, p. 733.)

Front 9

During photophosphorylation in plants, electrons flow through a series of carriers in the chloroplast. What is the ultimate donor of electrons, and what is the ultimate acceptor? What provides the energy to move those electrons?

Back 9

The ultimate donor is H2O, and the acceptor, NADP+. The energy that drives this electron flow is from light.

Front 10

Describe what happens when a photon is absorbed by photosystem II; end the description of electron flow at plastoquinone.

Back 10

Absorption of a photon by PSII excites P680 to P680*, which passes an electron to pheophytin, which passes the electron to plastoquinone. P680, now lacking an electron, takes one away from a “water-splitting complex” of PSII, which in turn takes one from H2O. (See Fig. 19-56, p. 739.)

Front 11

Chloroplasts are?

Back 11

specialized plasids

Front 12

What is the function of chloroplasts?

Back 12

House the photosynthic machery

Gather light and make ATP + NADPH

carbon fixation takes place

Front 13

What are the structures of chloroplasts?

Back 13

Double membrane:
Outer membrane
Inner membrane

Internal Thylakoid membrane

Front 14

What houses the photosynthic machery?

Back 14

Thylakoid membrane

Front 15

Thylakoid can be stacked or not stacked. What are the proper names?

Back 15

Stacked – Grana
Unstacked – Lamellae

Front 16

What is the Stroma?

Back 16

fluid around thylakoid

Front 17

Where are Kelvin enzymes are located?

Back 17

Stroma

Front 18

What are the major pigments in Chloroplasts?

Back 18

Chlorophyll a

Phycoerythrobilin

Front 19

What are the minor pigments in Chloroplasts?

Back 19

lutein

Beta-carotene

Front 20

What is the function of major pigments
in Chloroplasts?

Back 20

Good at absorbing visable light

Excites e-

Front 21

What is the function of minor pigments
in Chloroplasts?

Back 21

Protect chlorophyll
Extend range of light plant can use

Front 22

What does Light harvesting antennas do?

Back 22

Collect light and pass energy to the rxn center

Front 23

What does Exciton transfer with the help of light harvesting antennas?

Back 23

Energy

Not transferring e-, but energy the e- had

Front 24

What do rxn center of chloroplasts do?

Back 24

Converts light energy to chemical energy

Redox rxn to get charge separation

Front 25

What are the 6 steps to Conversion of light energy to chemical energy?

Back 25

Excitons verses Electrons
Excitation by light
Exciton transfer in antenna
Exciton transfer to reaction center
Electron transfer
Charge separation

Front 26

What are the steps in Z scheme?

Back 26

Light strikes photosystem II and the energy is absorbed and passed along until it reaches P680 chlorophyll.

The excited electron is passed to the primary electron acceptor. Photolysis in the thylakoid takes the electrons from water and replaces the P680 electrons that were passed to the primary electron acceptor. ( O2 is released as a waste product)

The electrons are passed to photosystem I via the electron transport chain (ETC) and in the process used to pump protons across the thylakoid membrane into the lumen.

The stored energy in the proton gradient is used to produce ATP which is used later in the Calvin-Benson Cycle.

P700 chlorophyll then uses light to excite the electron to its second primary acceptor.

The electron is sent down another ETC and used to reduce NADP+ to NADPH.

The NADPH is then used later in the Calvin-Benson Cycle.

Front 27

What does the z scheme accomplish?

Back 27

E- transfer from H2O to NADP+ in non-cyclic photosynthesis

Front 28

What is the position of cytochrome b6f in the Z scheme?

Back 28

cytochrome b6f is the link between PSII and PSI in the Z scheme

Front 29

What does cyt b6f is an integral?

Back 29

membrane proton pump

Front 30

What is the rxn formula in the Z scheme?

Back 30

PS II ~~> cyt b6f complex ~~> PS I

Front 31

What is another name for cytochrome b6f?

Back 31

plastoquinol—plastocyanin reductase

Front 32

The cytochrome b6f of chloroplasts and cyanobacteria does what?

Back 32

transfers electrons between the two reaction center complexes of oxygenic photosynthetic membranes, photosystem I and photosystem II

participates in formation of the transmembrane electrochemical proton gradient by also transferring protons from the stromal to the internal lumen compartment.

Front 33

The cytochrome b6f complex is responsible for?

Back 33

"non-cyclic" and "cyclic" electron transfer between two mobile redox carriers, plastoquinol (QH2) and plastocyanin

Front 34

What is cyt b6f composed of?

Back 34

It is minimally composed of four subunits:
cytochrome b6 (carrying a low- and a high-potential heme groups (bL and bH))
cytochrome f with one covalently bound heme c;
Rieske iron-sulfur protein (ISP) containing a single [Fe2S2] cluster;
and subunit IV (17 kDa protein).

Front 35

Facts of Type II Reaction Centers

Back 35

Pheophytin ~~> Quinone

– P870

P870 ~~> Pheo ~~> Q ~~> cybc1 ~~> cyt c2 ~~> back to P870 to start over

No O2 donor needed since it is an cyclic electron flow

Front 36

Cyclic electron flow of Type II Reaction Centers goes from?

Back 36

Pheophytin ~~> Quinone

Front 37

Type II Reaction Centers pathway is

Back 37

P870 ~~> Pheo ~~> Q ~~> cybc1 ~~> cyt c2 ~~> back to P870 to start over

Front 38

No O2 donor in Type II Reaction Centers needed since?

Back 38

it is a cyclic electron flow

Front 39

In its structure and functions, the cytochrome b6f complex bears extensive analogy to?

Back 39

the cytochrome bc1 complex of mitochondria and photosynthetic purple bacteria.

Front 40

What are the important differences between of the cytochrome b6f two complexes:

Back 40

The single-polypeptide cytochrome b in the cytochrome bc1 complex corresponds to cytochrome b6 and subunit IV in the cytochrome b6f complex

Cytochrome f and cytochrome c1 are not homologous

The cytochrome b6f complex contains additional chromophores, chlorophyll a, β-carotene and atypical heme ci (heme x), the latter being linked by a single thioether bond to cytochrome b6

Front 41

Green sulfur bacteria has what type of rxn center?

Back 41

Type I

Front 42

Facts of Type I Reaction Center

Back 42

Fe – S cluster

Pigment at the center– P840

• Cyclic electron flow
• Noncyclic electron flow

Front 43

The e – from Type I Reaction Center comes from either?

Back 43

e- is from either Q or ferredoxin

Front 44

Cyclic electron flow formula from Type I Reaction Center is?

Back 44

P840 ~~> Q ~~> cyt bc1 ~~> cyt c553 ~~> P840

Front 45

Non-Cyclic electron flow formula from Type I Reaction Center is?

Back 45

H2S ~~> P840 ~~> Fd ~~> Fd-NAD redux ~~> NAD+ ~~> NADH + H +

Front 46

Q from Cyclic electron flow formula from Type I Reaction Center does what?

Back 46

cycles back and makes gradient to make ATP

Front 47

Non-Cyclic electron flow Ferredoxin from Type I Reaction Center ends up in?

Back 47

NADH

Front 48

Position in the Z scheme in Photosystem I is

Back 48

Second and heads upward

Front 49

pathway of photosystem I is

Back 49

Plastocyan ~~> P700 ~~> Ao ~~> Phylloquinone ~~> 3 Fe – S cluster ~~> Ferredoxin

Front 50

Photosystem I facts:

Back 50

Macromolecular structure

Antenna complex

P700

Plastocyan to P700 ~~> Ao ~~> Phylloquinone ~~> 3 Fe – S cluster ~~> Ferredoxin

Front 51

What is the electron carriers used to transfer electrons from water to NADP+?

Back 51

P680, Plastoquinone, cyt f, plastocyanin, P700, ferredoxin

Front 52

Simple Non-cyclic electron flow Photosystem I pathway

Back 52

plastocyanin ~> P700 ~> Ferredoxin ~> NADP+

Front 53

In Photosystem I, What transferrs e- from ferredoxin to NADP+?

Back 53

Fd-NADP+ oxidoreductase

Front 54

Explain Cyclic electron flow

Back 54

plastocyanin ~> P700 ~> Ferredoxin ~~> Fd PQ oxidoreductase and wind up back on PQ ~~> cyt b6f and pump more protons that end up back to plastocyanin producing ATP but not NADPH

Front 55

Does photophosphorylation by cyclic electron flow around PSI produce O2?

Back 55

No cause electron are recycled during this process so there is no need to oxidize H20

Front 56

ATP synthase is made of what two important subunits for transporting H + thur matrix of Mitochondria

Back 56

Complex Fo, F1

Front 57

What make up the proton motive force?

Back 57

A chemical (delta pH) and an electrical component make up the proton motive force.

Front 58

ATP is synthesized from _____ by ______

Back 58

ADP and Pi by ATP synthase in the inner mitochondria membrane.

Front 59

ATP synthase takes place where?

Back 59

in the inner mitochondria membrane.

Front 60

Fo subunit of ATP synthase is what type of complex?

Back 60

A membrane spanning protein complex

Front 61

Where is F1 is located?

Back 61

F1 is located on the matrix side of the inner membrane

Front 62

Because the inner membrane is impermeable to H+, the only path for protons to reenter the matrix is through?

Back 62

the pore formed by the Fo subunit of ATP synthase.

Front 63

ADP is phosphorylated by the enzymatic activity of the _______ driven by_____.

Back 63

F1 complex, driven by the PMF

Front 64

What is Photosystem I Relation to the Z scheme?

Back 64

Pumping protons either cyclic or non cyclic to generate ATP

Front 65

What ends up in the grana of the thylakoid?

Back 65

most PSII, cyt bcf, light harvesting complex II(P116) (LHCII )

Front 66

most PSII, cyt bcf, light harvesting complex II(P116) (LHCII ) ends up here

Back 66

the grana of the thylakoid

Front 67

What ends up in the lamallae of the thylakoid?

Back 67

PSI, ATP synthase, cyt b6f, LHCII

Front 68

PSI, ATP synthase, cyt b6f, LHCII ends up here

Back 68

Lamallae

Front 69

What shows up in both the grana and lamellae?

Back 69

LHCII (P116)

Front 70

Why are PS I and PSII separated?

Back 70

Prevention of exciton latency by spatial separation of PSI and PSII

better access to substrates

Control of electron flow via LHCII

Front 71

exciton latency is?

Back 71

Passing e- to the wrong photosystem

Front 72

What PS requires less energy excitation?

Back 72

PS I

Front 73

What needs Access to substrates that is provided by Organization of photosynthetic complexes

Back 73

ATP synthase needs access to ATP and Pi. (Out on lamellae, it is available to its substrates)

PSI ~~> NADP+

Front 74

Why is organization of photosynthetic complexes
So important?

Back 74

Prevents exciton latency and allows access to substrates

Front 75

What is the result in a high ratio of reduced plastoquinone to oxidized plastoquinone (PQH2/PQ)

Back 75

Over active of PSII and under active PSI

Over active of PSII, you will get reduced plastoquinone and not an oxidized plastoquinone

Front 76

In regards to organization of photosynthetic complexes, controlling where LHCII is located will allow you to?

Back 76

control where these photo e- are passed

Front 77

What is Complex IV called?

Back 77

Cytochrome c oxidase

Front 78

Complex IV is composed of subunits and its molecular size is

Back 78

13 subunits
204,000

Front 79

How many Critical subunits of cytochrome c oxidase. (complex IV)

Back 79

Three subunits

Front 80

Critical subunits of cytochrome c oxidase.

Back 80

(a) Subunit 1has two heme groups a and a3(red), and a Cu ion, CuB (green). The heme and Cu form a Fe-Cu Center.
(b) Subunit 2 (blue) has 2 Cu ions, CuA. Subunit 2 has the Cyt c binding site.
(c) Subunit 3 (green) is important but its function is not known.

Front 81

What is in Subunit 1 of cytochrome c oxidase. (complex IV)?

Back 81

Subunit 1 has two heme groups a and a3(red), and a Cu ion, CuB (green). The heme and Cu form a Fe-Cu Center.

Front 82

In what subunit of Complex IV is the heme and Cu form a Fe-Cu Center?

Back 82

Subunit 1

Front 83

What is in Subunit 2 of cytochrome c oxidase. (complex IV)?

Back 83

Subunit 2 has 2 Cu ions, (CuA & CuB), and the Cyt c binding site.

Front 84

What is in Subunit 3 of cytochrome c oxidase. (complex IV)?

Back 84

Subunit 3 is important but its function is not known.

Front 85

In Complex 4, Where is the binuclear center of CuA located?

Back 85

Subunit 2

Front 86

What is different about the binuclear center of CuA of Complex IV?

Back 86

The 2 Cu ions share electrons equally.

Front 87

When the binuclear center of CuA of Complex IV is reduced, They are?

Back 87

Cu+1, Cu+1.

Front 88

When the binuclear center of CuA of Complex IV is oxidized they are?

Back 88

Cu+1.5, Cu+1.5.

Front 89

When the binuclear center of CuA of Complex IV is oxidized they are Cu+1.5, Cu+1.5. Why?

Back 89

They share an electron

Front 90

What is the Complex IV e- pathway?

Back 90

2 molecules of reduced cytochrome c each donate an electron to binuclear center CuA.

Then the electrons are passed to heme a to the Fe-Cu center (cytochrome a3 and CuB).

O2 now binds to heme a3 and is reduced to its peroxy derivative (O2 2-) by 2 electrons from the Fe-Cu center.

Two more electrons from cyt c converts the (O2) 2- to two molecules of H2O with 4 H+ from the matrix.

In addition 4 more protons are pumped
from the matrix (N side) to to the P side by an
unknown mechanism.

Front 91

Why must The complex I -IV have a intact membrane?

Back 91

So e- won’t leak out and proton gradient can form

Front 92

The Complex IV reaction may be thought of as?

Back 92

4 cyt c (reduced) + 8 H+ N + O2 →4 cyt c (oxidized) + 4H+ P + 2 H2O

Front 93

How much energy in formed by the complexs?

Back 93

220 kJ/mol of energy is released and this energy is reserved by the set up of the proton gradient + separation of charges. (termed the Proton-motive force).

Front 94

The energy formed by the complexs this energy is reserved by?

Back 94

the set up of the proton gradient + separation of charges. (termed the Proton-motive force).
It is estimated that about 200 kJ/mole are conserved in the gradient.

Front 95

What is the Proton-motive force?

Back 95

the set up of the proton gradient + separation of charges from energy that is formed in the Complexs

Front 96

The synthesis of ATP from ADP and Pi is driven by utilization of the energy generated by?

Back 96

the proton gradient + the charge difference (electron potential) in the membrane

Front 97

What is driven by utilization of the energy generated by the proton gradient + the charge difference (electron potential) in the membrane.

Back 97

synthesis of ATP from ADP and Pi

Front 98

The chemical mechanism that couples the energy obtained from the proton gradient to phosphorylation of ADP to form ATP is called the

Back 98

chemiosmotic model or theory.

Front 99

Explain the Chemiosmotic Model?

Back 99

Electrons from NADH and other oxidizable substrates pass through a chain of carriers arranged
asymmetrically in the inner membrane.
Accompanying e- flow is a proton transfer
producing a pH (proton) gradient between the
intermembrane space and the matrix. Protons
are not permeable to the mitochondrial
membrane and can only get to the matrix
through a specific channel, Fo. The proton
motive force energy drives protons back into
the matrix providing energy for ATP synthesis that is catalyzed by ATP synthase.

Front 100

What is the short explanation of Chemiosmotic Model?

Back 100

Electrons from NADH and other oxidizable substrates pass through a chain of carriers arranged asymmetrically in the inner membrane.

Front 101

In Chemiosmotic Model, Accompanying e- flow is a proton transfer producing?

Back 101

a pH (proton) gradient between the intermembrane space and the matrix.

Front 102

In Chemiosmotic Model, Accompanying e- flow is __________ producing a pH (proton) gradient between the intermembrane space and the matrix.

Back 102

a proton transfer

Front 103

Protons are not permeable to the mitochondrial
membrane and can only get to the matrix through by?

Back 103

a specific channel, Fo.

Front 104

In the Chemiosmotic Model, What drives protons back into the matrix providing energy for ATP synthesis that is catalyzed by ATP synthase.

Back 104

proton motive force energy

Front 105

In the Chemiosmotic Model, The proton motive force energy drives protons back into the matrix providing energy for ATP synthesis that is catalyzed by?

Back 105

ATP synthase.

Front 106

In the Chemiosmotic Model, The proton motive force energy drives protons back into the matrix providing?

Back 106

energy for ATP synthesis


ATP synthesis is coupled to O2 consumption. Thus when a TCA metabolite or substrate metabolite is oxidized in the mitochondria (eg., succinate) the proton gradient occurs during O2 consumption driving ATP synthesis. That is why the process is called Oxidative Phosphorylation

Front 107

ATP synthesis is coupled to?

Back 107

O2 consumption.

Front 108

when a TCA metabolite or substrate metabolite is oxidized in the mitochondria (eg., succinate) the
proton gradient occurs during?

Back 108

O2 consumption driving ATP synthesis. That is why the process is called Oxidative Phosphorylation.

Front 109

What is Oxidative Phosphorylation

Back 109

The proton gradient occurs during O2 consumption driving ATP synthesis.

Front 110

Coupling of electron transfer and ATP synthesis in mitochondria, Addition of ADP and Pi alone results in?

Back 110

little or no increase in either O2 consumption or ATP synthesis

Front 111

What causes causes immediate respiration and ATP synthesis in Oxidative Phosphorylation.

Back 111

Succinate addition

Front 112

What inhibits cytochrome oxidase, inhibits both O2 consumption and ATP synthesis in Oxidative Phosphorylation.

Back 112

Addition of CN-

Front 113

In Oxidative Phosphorylation, Succinate addition alone does not cause respiration but does occur when?

Back 113

ADP + Pi are added

Front 114

In Oxidative Phosphorylation,What blocks both ATP synthesis and respiration.

Back 114

oligomycin and venturicidin

Front 115

What are Inhibitors of ATP synthase,?

Back 115

oligomycin and venturicidin

Front 116

What does oligomycin and
Venturicidin do to in Oxidative Phosphorylation?

Back 116

Inhibitors of ATP synthase

Front 117

In Oxidative Phosphorylation,What allows respiration to go on but inhibits ATP synthesis?

Back 117

dinitrophenol (DNP)
which is uncoupler compound

Front 118

In Oxidative Phosphorylation, an uncoupler compound dinitrophenol (DNP) allows respiration to go on but inhibits ATP synthesis. This is because?

Back 118

The uncoupler is able to dissipate the proton or pH gradient

Front 119

In Oxidative Phosphorylation, an uncoupler compound dinitrophenol (DNP) does what?

Back 119

allows respiration to go on but inhibits ATP synthesis.

Front 120

How do the uncoupling agents, DNP and (FCCP) uncouple respiration from ATP synthesis?

Back 120

both FCCP and DNP are Weak acids, having a dissociable H+ and are hydrophobic. This allows them to cross the mitochondrial membrane. They can carry protons across the membrane and dissipate the pH or proton gradient.

Front 121

What allows FCCP and DNP to cross the mitochondrial membrane and can carry protons across the membrane and dissipate the pH or proton gradient.

Back 121

both FCCP and DNP are Weak acids, having a dissociable H+ and are hydrophobic

Front 122

What compounds interfere with oxidative phosphorylation?

Back 122

Cyanide
Carbon monoxide
Antimycin A
Rotenone
Oligomycin
DNP

Front 123

Cyanide interferes with oxidative phosphorylation

Type of interference:
Target/mode of action:

Back 123

Type of interference: inhibition of electron transfer

Target/mode of action: inhibit cytochrome oxidase

Front 124

Carbon monoxide interferes with oxidative phosphorylation

Type of interference:
Target/mode of action:

Back 124

Type of interference: inhibition of electron transfer

Target/mode of action: inhibit cytochrome oxidase

Front 125

Antimycin A interferes with oxidative phosphorylation

Type of interference:
Target/mode of action:

Back 125

Type of interference: inhibition of electron transfer

Target/mode of action: Blocks electron transfer from cytochrome b to c1

Front 126

Rotenone interferes with oxidative phosphorylation

Type of interference:
Target/mode of action:

Back 126

Type of interference: inhibition of electron transfer

Target/mode of action: Prevent electron transfer from Fe-S center to ubiquinone

Front 127

Oligomycin interferes with oxidative phosphorylation

Type of interference:
Target/mode of action:

Back 127

Type of interference: Inhibition of ATP synthase
Target/mode of action: inhibits Fo and CFo

Front 128

DNP interferes with oxidative phosphorylation

Type of interference:
Target/mode of action:

Back 128

Type of interference: Uncoupling of phosphorylation from electron transfer

Target/mode of action: Hydrophobic proton carriers

Front 129

What compounds have the inhibition of electron transfer-type of interference?

Back 129

Cyanide
Carbon monoxide
Antimycin A
Rotenone

Front 130

What compounds have the inhibit cytochrome oxidase - type mode of action?

Back 130

Cyanide
Carbon monoxide

Front 131

Can an artificially created proton gradient replace electron transfer and cause ATP Synthesis?

Back 131

yes. Mitochondria can be manipulated to create a proton gradient in the absence of oxidizable substrate
and can cause ATP synthesis.

Front 132

What is the evidence for the role of a proton
gradient in ATP synthesis?

Back 132

First incubation. pH 9.0 buffer in presence of 0.1M
KCl.

Slow leakage of buffer and KCl into mito eventually brings the matrix into equilibrium w/ surrounjding medium

Second incubation.

Mitochondria is moved to Buffer of pH 7.0 w/ Valinomycin and no K+ added. The Valinomycin added to buffer is to transport K+
out of matrix creating a charge imbalance. This coupled with the proton gradient is sufficient to observe ATP synthesis.

The outward flow of K+ carried by Valinomycin down its concentration gradient w/o a counterion, creating a charge imbalance across the membrane

The sum of the chemical potential provided by the pH difference and the electrical potential provided by the separation of charges is a protonmotive force large enough to support ATP synthesis in the absence of an oxidizable substrate.

Front 133

Describe the first incubation of the evidence for the role of a proton gradient in ATP synthesis?

Back 133

First incubation. pH 9.0 buffer in presence of 0.1M
KCl. Slow leakage of buffer and KCl into mito eventually brings the matrix into equilibrium w/ surrounjding medium

Front 134

Describe the Second incubation of the evidence for the role of a proton gradient in ATP synthesis?

Back 134

Mitochondria is moved to Buffer of pH 7.0 w/ Valinomycin and no K+ added. The Valinomycin added to buffer is to transport K+
out of matrix creating a charge imbalance. This coupled with the proton gradient is sufficient to observe ATP synthesis.

The outward flow of K+ carried by Valinomycin down its concentration gradient w/o a counterion, creating a charge imbalance across the membrane

Front 135

The sum of the chemical potential provided by the pH difference and the electrical potential provided by the separation of charges provided for the role of a proton gradient in ATP synthesis is a?

Back 135

Proton motive force large enough to support ATP synthesis in the absence of an oxidizable substrate.

Front 136

When the complex is solubilized and purified it causes?

Back 136

hydrolysis of ATP to ADP and Pi.

Front 137

When the complex is solubilized and purified it causes hydrolysis of ATP to ADP and Pi. When will the complex be able to synthesize ATP?

Back 137

complex be able to synthesize ATP when the complex is situated in the mitochondria and in the presence of a proton gradient

Front 138

There is a F0 integral membrane protein complex with subscript 0 indicationg that?

Back 138

oligomycin inhibits the synthase by binding to the F0 complex.

Front 139

F0 provides a transmembrane pore for?

Back 139

protons.

Front 140

Explain the F1 domain?

Back 140

The F1 domain consists of three  subunits three  subunits and one delta subunit.

The  and subunits alternate with each other.

The central shaft is the y subunit that connects along
with the  subunit F1 to F0.

The F0 complex has 10 c subunits, an a and two b subunits.

Front 141

The F1 domain consists of?

three  subunits three  subunits and one delta subunit.

The  and subunits of the F1 domain do what with each other?

Back 141

alternate with each other.

Front 142

The central shaft of the F1 domain is the y subunit that connects along with the?

Back 142

 subunit F1 to F0.

Front 143

The central shaft of the F1 domain is the? subunit

Back 143

Y (delta)

Front 144

The F0 complex has how many subunits?

Back 144

10 c subunits, an a subunit and two b subunits.

Front 145

how does the delta G’0 for ATP synthesis is close to 0?

Back 145

ATP binds to the synthase at about Kd of 10-12 M while ADP binds only at only Kd of 10-5M.

This difference in binding corresponds to a difference of 40 kJ/mol in binding energy.

Because the hydrolysis of ATP in free solution is -30.5 kJ/mol, the relatively tight binding of ATP on the surface of the ATP synthase explains how the delta G’0 for ATP synthesis is close to 0

Front 146

The beta subunit of the F1 complex can assume how many different conformations?

Back 146

three

Front 147

The subunit in the stalk is associated with?

Back 147

one of the  subunits as well having one of its domain passing through F1.

Front 148

What explains  subunits ability to bind ATP and ADP differently?

Back 148

 subunits are in different conformations at all times

The subunit in the stalk is associated with one of the  subunits as well having one of its domain passing through F1. Thus the  subunits are?

in different conformations and this explains their ability to bind ATP and ADP differently.

Front 149

Explain the different conformations of  subunits?

Back 149

One has been found to bind ATP, another ADP
and the third has an empty site. Thus the conformations are known as - ATP, -ADP -empty and this has significance to the ATP synthase enzyme mechanism.

Front 150

What are known as - ATP, -ADP -empty?

Back 150

One  subunits has been found to bind ATP, another  subunits bind to ADP and the third  subunits has an empty site.

Front 151

the and of the ATP synthase are ______ & ___________

Back 151

in pairs and work together in the enzyme mechanics

Front 152

What is the Binding Change Mechanism for ATP Synthesis?

Back 152

A Rotational catalysis mechanism is proposed for ATP synthesis in where the active sites of F1 take turns catalyzing ATP synthesis. One  -subunit is in the ADP conformation, binding ADP + Pi. Another subunit has tightly bound ATP and the third −
subunit pair is empty.

Front 153

The proton-motive force causes rotation of the central shaft subunit that comes into rotation with each −pair in succession. This causes?

Back 153

each −pair to change in conformation.

Front 154

The proton-motive force causes rotation of the central shaft subunit that comes into rotation with each −pair in succession. This causes each −pair to change in conformation. Name change of conformations?

Back 154

−ATP becomes −empty releasing the ATP,

−ADP becomes −ATP and the ADP and Pi bound to it is converted to ATP.

The −empty site becomes −ADP which then loosely binds ADP +Pi.

Front 155

all −pair sites alternate in activity and ATP cannot be released from one site until?

Back 155

ADP and Pi are bound to another.

Front 156

How many ATP are synthesized with oxidation of NADH and of succinate?

Back 156

The overall reaction is: xADP + xPi + 1/2 O2 + H+ + NADH (increase) xATP + H2O + NAD+

X is sometimes called the P/O ratio or P/2e- ratio.

Front 157

Explain the P/O ratio or P/2e- ratio?

Back 157

In practical experiments it was found that the P/O ratio (= to ATP/ 1/2 O2 ) for NADH was between 2 and 3 and for succinate to be between 1 and 2. It was believed that one ATP was coupled with Complex I oxidation, another with complex III and one with complex IV. Thus the P/O ratio was 3.0. Since
The conformational changes for the model are driven by the passage of protons through the F0 portion of the ATP synthase.

Front 158

The conformational changes for the binding change model are driven by?

Back 158

the passage of protons through the F0 portion of the ATP synthase.

Front 159

What causes rotation of the cylinder of c subunits and subunit in conformational changes for the binding change model?

Back 159

the passage of protons through the F0 portion of the ATP synthase.

Front 160

The subunit in contact with a −pair of the binding change model becomes?

Back 160

a - empty subunit in conformation.