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Biochem > Oxidative Phosphorylation > Flashcards

Oxidative Phosphorylation Flashcards

1
Q

How is energy from the ETC used?

A

Energy from the electron transfer/proton pumping converted into high phosphoryl transfer potential energy

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2
Q

________ and ________ occur together

A

Electron flow and proton pumping

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3
Q

Flow of electrons from NADH to O2 is a __________ reaction

A

Exergonic

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4
Q

1 NADH = ______ ATP

A

2.5 ATP

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5
Q

1 FADH2 = ______ ATP

A

1.5 ATP

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6
Q

No proton pumping occurs in ______

A

Complex II

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7
Q

Mitchell’s Chemiosmotic Hypothesis

A

There is a proton gradient across the inner mitochondrial membrane and it could be used to drive ATP synthesis

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8
Q

2 components of the gradient

Creates?

A
  1. Chemical (pH) gradient
  2. Electrical gradient (charges)

Create an ELECTROCHEMICAL gradient

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9
Q

Matrix pH vs. intermembrane space pH

A

Matrix pH = 8.0

Intermembrane space pH = 6.0

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10
Q

_________ drives the protonation / deprotonation of the _________ residues on the _____________

A

The chemical (pH) gradient

Aspartic acid

C subunits

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11
Q

Inner mitochondrial leaflet facing matrix is _______ charge

A

Negative

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12
Q

Inner mitochondrial leaflet facing outer membrane is ______ charge

A

Positive

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13
Q

Electrochemical potential

A

Potential energy driving H+ to return to the matrix

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14
Q

Complexes pump protons into the ___________ creating _________

A

Protons are pumped into the intermembrane space creating the proton motive force

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15
Q

As proton flow back into the _______ through ________, the ______ drive the synthesis and dissociation of ________

A

Matrix
ATP synthase
Proton motive force
ATP

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16
Q

F0 domain of ATP synthase

structure and location

A
  • Located in the inner membrane
  • Made up of individual C subunits
  • “A” region is the pore consisting of 2 half channels
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17
Q

Proton flow through the F0 region of ATP synthase

A

Proton from IMS enters —> protonates aspartic acid side chain (COO- becomes protonated) on C subunit —> C subunit advanced until you get another C subunit and another proton entering through half channel —> entire C ring rotates until every subunit is protonated —> whatever C subunit is lined up with the matrix half channel, proton goes through and returns to the matrix —> COO- is restored

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18
Q

What amino acid undergoes protonation/deprotonation in the C subunits?

A

Aspartic acid

COO- group

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19
Q

F1 domain of ATP synthase

Important subunits (4)?

A

Gamma
Beta
Alpha
B2

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20
Q

Gamma subunit of F1 domain

Function and importance

A

Serves like a rotor

As C ring turns based on movement of protons, the gamma subunit rotates and drives different conformational changes in the alpha and beta subunits

Importance: Connects movement of C ring with the conformational changes of alpha and beta subunits

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21
Q

Alpha subunit of F1 domain

Importance and function?

A

NO role in ATP synthesis

Importance: To F1 domain structure and function…conformational changes

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22
Q

Beta subunit of F1 domain

Function

A

Synthesis and release of ATP

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23
Q

B2 subunit of F1 domain

Function?

A

Synchronize the rotation of pore with the gamma subunit and the alpha and beta subunits

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24
Q

____ different conformations that each ______ subunit can undergo.

Depends on the _______________ —> which is determined by ___________ —> which is dependent on

A

3 different conformations that each beta subunit can undergo

Depends on the beta subunit interaction with gamma —> which is determined by the rotation of the C ring —> which is dependent on H+ movement

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25
Q

What are the 3 different conformations that each beta subunit of the F1 domain can undergo ?

A
  1. O “open”
  2. L “loose
  3. T “tight”
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26
Q

O “open” conf of beta subunit

A

Bring in ADP and Pi

Release ATP

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27
Q

L “loose” conf of beta subunit

A

Binding of ADP + Pi

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28
Q

T “tight” conf of beta subunit

A

ATP is made but is still bound tightly

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29
Q

Glycolysis

ATP calculation
NADH calculation

A

2 ATP in
2 ATP made using 1,3-BPG (even)
2 ATP made using phosphoenolpyruvate (net)

2 NADH made by oxidizing glyceraldehyde 3-phosphate

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30
Q

(2) Types of shuttles that can be used to transport NADH from the cytoplasm into the mitochondria?

Located where?

A
    1. Glycerol 3-phosphate shuttle (muscle)

2. Malate-aspartate shuttle (heart and liver)

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31
Q

Glycerol 3-phosphate shuttle gives ____ ATP per 1 NADH.

Why?

A

1.5 ATP per 1 NADH

FAD is used as shuttle prosthetic group —> donor of those e- to ETC is FADH2

32
Q

Glycerol 3-phosphate shuttle mechanism

A
  1. In cytoplasm, glycolytic intermediate dihydroxyacetone phosphate accepts e- from NADH to regenerate NAD+ catalyzed by cytoplasmic glycerol 3-phosphate dehydrogenase.
  2. Becomes glycerol 3-phosphate
  3. Donates e- to mitochondrial glycerol 3-phosphate dehydrogenase which used FAD as shuttle prosthetic group
  4. FADH2 donates those e- to ETC complex II
33
Q

PDC

NADH calculations

A

2 NADH

34
Q

Citric acid Cycle

ATP, NADH, FADH2 calculations

A

2 ATP using 2 succinyl CoA

6 NADH by oxidizing 2 molecules each of isocitrate, alpha-ketoglutarate, and malate

2 FADH2 by oxidizing 2 molecules of succinate

35
Q

Total ATP per 1 glucose

but…

A

30

Amount can differ slightly between organisms because C subunits can vary.

More C subunits —> More H+ able to bind —> More ATP can be made

36
Q

Electron transfer and _________ are tightly coupled

A

ATP synthesis

37
Q

ATP synthesis correlates to?

2

A

How fast ATP is used or needed in the cell

  1. Rate of ATP utilization
  2. Rate of oxygen consumption
38
Q

Blocking of ETC at any point ___________

A

Prevents ATP synthesis

39
Q

Blocking/inhibiting ATP synthase ______________ because?

A

Slows down ETC because buildup of NADH which feeds back and negatively allosterically modifies enzymes

40
Q

Rate of ATP utilization:

If use ATP —>

What in mitochondria determines how fast ETC goes?

A

If use ATP —> elevated ADP and AMP —> make more ATP

ADP in mitochondria

(All other types of regulation we’ve talked about still applies)

41
Q

Rate of oxygen consumption:

Make ATP use —>

A

Make ATP use —> faster ETC —> increase O2 consumption

42
Q

If metabolism increases ……

A

Increased blood flow to tissues (skel muscle) —> deliver more O2 via hemoglobin to tissues to carry out aerobic respiration

Because metabolizing, H+ and CO2 are produced —> make up Bohr effect which also promotes O2 delivery to tissues

43
Q

In vitro system with isolated mitochondria

Measures?
What happens when ADP is added? Explain.

A

Measures O2 consumption over time

When ADP is added —> rapid rate of O2 consumption

Therefore, this explains that ADP increases the rate of ETC because need to make more ATP and increase the rate of O2 consumption

44
Q

O2 consumption is a measure of ?

A

The rate of the ETC

45
Q

If you are using ATP —> _____ conc rise and _________

A

ADP conc increases —> ETC increases to continue to maintain proton gradient (pmf)

46
Q

ETC senses the ________

A

Proton motive force

47
Q

When the pmf drops because more protons are going through ATP synthase to make ATP, what happens?

A

The drop in pmf is a signal to the ETC to increase

48
Q

If need ATP generation…..

A

ETC works harder so needs a source of e- and H+ from NADH and FADH2

Get those from TCA cycle so that will increase too because of NAD+ and FADH regeneration

49
Q

If stop ATP generation, what happens?

A

pmf rises —> ETC slows —> less NADH oxidized to NAD+ —> NADH feeds back and inhibits enzymes

50
Q

__________ controls the rate of O2 consumption.

A

ADP concentration

51
Q

__________ is dependent on its rate of utilization.

A

ATP synthesis

52
Q

Electrons do not flow from fuel oxidation to O2 unless _________.

A

ATP needs to be synthesized/consumed

53
Q

How is ATP and ADP transported across the inner mitochondrial membrane?

A

Enzyme: ATP-ADP translocase
Which is located in the inner mitochondrial membrane

*An even exchange: ADP enters only if ATP exists, ATP does not exit unless ADP comes in

54
Q

Process of ADP - ATP even exchange

A

ADP from cytoplasm binds to ATP-ADP translocase —> conf change so now ADP is exposed to the matrix of mitochondria —> ADP released into mitochondria —> ATP from matrix binds to that site —> reverse conf change —> ATP released into cytoplasm

55
Q

3 mechanisms of ATP synthesis

A
  1. Respiratory inhibitors
  2. Direct inhibition of ATP synthase
  3. Uncouplers
56
Q

Significance of respiratory inhibitors

A

Blocks the transfer of electrons at various points therefore ATP synthase is also blocked.

57
Q

Consequence of respiratory inhibitors

A

ATP synthesis inhibited.

58
Q

Rotenone and amytal

A
  • Block Complex I
  • Electrons don’t move to CoQ —> NADH builds up —> TCA cycle slows down because NADH is negative allosteric modifier of isocitrate dehydrogenase
59
Q

Antimycin A

A

Inhibits complex III

60
Q

CN- , N3- , CO

A
  • All inhibit complex IV
  • CN- and N3- bind to Fe3+ of heme a3
  • CO binds to Fe2+ of heme a3
  • Prevent the oxidation/reduction because if the iron becomes reduced it eventually has to be reset to be oxidized if it is going to accept more electrons to keep the reaction going.
  • PREVENT THE RELEASE OF ELECTRONS TO OXYGEN
61
Q

CO affects both?

A

Oxygen delivery and mitochondrial respiration/ability to generate ATP

— — > can only survive by glycolysis

62
Q

Direct inhibition of ATP synthase

  • 2 examples

Consequence?

A

Ex: Oligomycin - inhibits F0

Ex: DCCD

Consequence: ETC is inhibited and ATP synthesis is inhibited.

63
Q

Uncouplers

  • 2 types
  • Consequence
A
  • Can be chemical or physiological

Consequence: Disrupt the tight coupling between electron transport and oxidative phosphorylation by dissipating the proton gradient —> NO ATP SYNTHESIS

64
Q

Mechanism of uncouplers

A

Carry protons back into matrix independent of ATP synthase

Pmf drops —> ETC rate increases —> TCA cycle increases —> “burning fuel with no ATP synthesis”

65
Q

2 things that occur due to uncoupling

Explain each.

A
  1. Energy is released as heat- physiological advantage is maintenance of body temp
  2. Excessive oxygen consumption- utilization of substrate and electron still occur but no proton gradient and no ATP formed
66
Q

Chemical uncouplers

General properties (2)

A
  • Hydrophobic

- Have a dissociable proton therefore have a pKa and are subject to pH gradient in mitochondria

67
Q

Chemical uncouplers are ________ in IMS and ________ in matrix

A

Protonated in IMS

Deprotonated in matrix

68
Q

Mechanisms of chemical uncouplers

A

Protons do not go through F0 —> pmf decreases —> ETC increases —> TCA increases —> no ATP being made —> energy lost as heat

69
Q

Examples of chemical uncouplers (3)

A
  • Dinitrophenol
  • Dicumarol
  • FCCP
70
Q

Physiological uncoupler example

A

UCP-1

71
Q

UCP-1

Where?
Activated by?
Does what?

A
  • Integral proton channel in mitochondrial membrane
  • Activated by fatty acids
  • Brings H+ into the matrix independent of ATP synthase

Advantage: generating heat

72
Q

In hibernating animals, ________ increases in activity to ________. What allows this to occur?

A

UCP-1

To maintain body temp for normals processes when metabolic rate slows down.

Excess adipose tissue

73
Q

Brown adipose tissue in infants

A

Thermogenin (UCP-1) highly expressed here

Because not yet developed full ability to regulate their body temperature

74
Q

Brown adipose tissue in adult humans

A
  • Not lipid storage

- Highly metabolic, lots of mitochondria

75
Q

Exposure to cold PET-CT scan result

A
  • Stimulates sympathetic NS

- Found that BAT accumulates in shoulder blades and chest area

76
Q

Lean vs. Obese study result in adults

A
  • Given ephedrine which also stimulates sympathetic NS
  • BAT not activated in obese people (Could BAT stimulation help lose weight by promoting burning stored fat?)
  • BAT in lean people activated in same areas as cold exposure study

Biochem (15 decks)

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