Oxidative Phosphorylation Flashcards Preview

MCB 2000 > Oxidative Phosphorylation > Flashcards

Flashcards in Oxidative Phosphorylation Deck (76):
1

How is energy from the ETC used?

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

2

________ and ________ occur together

Electron flow and proton pumping

3

Flow of electrons from NADH to O2 is a __________ reaction

Exergonic

4

1 NADH = ______ ATP

2.5 ATP

5

1 FADH2 = ______ ATP

1.5 ATP

6

No proton pumping occurs in ______

Complex II

7

Mitchell’s Chemiosmotic Hypothesis

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

8

2 components of the gradient

Creates?

1. Chemical (pH) gradient

2. Electrical gradient (charges)

Create an ELECTROCHEMICAL gradient

9

Matrix pH vs. intermembrane space pH

Matrix pH = 8.0

Intermembrane space pH = 6.0

10

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

The chemical (pH) gradient

Aspartic acid

C subunits

11

Inner mitochondrial leaflet facing matrix is _______ charge

Negative

12

Inner mitochondrial leaflet facing outer membrane is ______ charge

Positive

13

Electrochemical potential

Potential energy driving H+ to return to the matrix

14

Complexes pump protons into the ___________ creating _________

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

15

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

Matrix
ATP synthase
Proton motive force
ATP

16

F0 domain of ATP synthase

structure and location

- Located in the inner membrane

- Made up of individual C subunits
- “A” region is the pore consisting of 2 half channels

17

Proton flow through the F0 region of ATP synthase

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

18

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

Aspartic acid

(COO- group)

19

F1 domain of ATP synthase

Important subunits (4)?

Gamma
Beta
Alpha
B2

20

Gamma subunit of F1 domain

Function and importance

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

21

Alpha subunit of F1 domain

Importance and function?

NO role in ATP synthesis

Importance: To F1 domain structure and function...conformational changes

22

Beta subunit of F1 domain

Function

Synthesis and release of ATP

23

B2 subunit of F1 domain

Function?

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

24

____ different conformations that each ______ subunit can undergo.

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

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

25

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

1. O “open”

2. L “loose

3. T “tight”

26

O “open” conf of beta subunit

Bring in ADP and Pi

Release ATP

27

L “loose” conf of beta subunit

Binding of ADP + Pi

28

T “tight” conf of beta subunit

ATP is made but is still bound tightly

29

Glycolysis

ATP calculation
NADH calculation

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

30

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

Located where?

* 1. Glycerol 3-phosphate shuttle (muscle)

2. Malate-aspartate shuttle (heart and liver)

31

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

Why?

1.5 ATP per 1 NADH

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

32

Glycerol 3-phosphate shuttle mechanism

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

PDC

NADH calculations

2 NADH

34

Citric acid Cycle

ATP, NADH, FADH2 calculations

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

Total ATP per 1 glucose

but...

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

Electron transfer and _________ are tightly coupled

ATP synthesis

37

ATP synthesis correlates to?

(2)

How fast ATP is used or needed in the cell

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

38

Blocking of ETC at any point ___________

Prevents ATP synthesis

39

Blocking/inhibiting ATP synthase ______________ because?

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

40

Rate of ATP utilization:

If use ATP —>

What in mitochondria determines how fast ETC goes?

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

Rate of oxygen consumption:

Make ATP use —>

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

42

If metabolism increases ......


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

In vitro system with isolated mitochondria

Measures?
What happens when ADP is added? Explain.

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

O2 consumption is a measure of ?

The rate of the ETC

45

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

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

46

ETC senses the ________

Proton motive force

47

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

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

48

If need ATP generation.....

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

If stop ATP generation, what happens?

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

50

__________ controls the rate of O2 consumption.

ADP concentration

51

__________ is dependent on its rate of utilization.

ATP synthesis

52

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

ATP needs to be synthesized/consumed

53

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

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

Process of ADP - ATP even exchange

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

3 mechanisms of ATP synthesis

1. Respiratory inhibitors

2. Direct inhibition of ATP synthase

3. Uncouplers

56

Significance of respiratory inhibitors

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

57

Consequence of respiratory inhibitors

ATP synthesis inhibited.

58

Rotenone and amytal

- 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

Antimycin A

Inhibits complex III

60

CN- , N3- , CO

- 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

CO affects both?

Oxygen delivery and mitochondrial respiration/ability to generate ATP

— — > can only survive by glycolysis

62

Direct inhibition of ATP synthase

- 2 examples

Consequence?

Ex: Oligomycin - inhibits F0

Ex: DCCD

Consequence: ETC is inhibited and ATP synthesis is inhibited.

63

Uncouplers

- 2 types
- Consequence

- 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

Mechanism of uncouplers

Carry protons back into matrix independent of ATP synthase

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

65

2 things that occur due to uncoupling

Explain each.

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

Chemical uncouplers

General properties (2)

- Hydrophobic

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

67

Chemical uncouplers are ________ in IMS and ________ in matrix

Protonated in IMS

Deprotonated in matrix

68

Mechanisms of chemical uncouplers

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

69

Examples of chemical uncouplers (3)

- Dinitrophenol

- Dicumarol

- FCCP

70

Physiological uncoupler example

UCP-1

71

UCP-1

Where?
Activated by?
Does what?

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

Advantage: generating heat

72

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

UCP-1

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

Excess adipose tissue

73

Brown adipose tissue in infants

Thermogenin (UCP-1) highly expressed here

Because not yet developed full ability to regulate their body temperature

74

Brown adipose tissue in adult humans

- Not lipid storage
- Highly metabolic, lots of mitochondria

75

Exposure to cold PET-CT scan result

- Stimulates sympathetic NS

- Found that BAT accumulates in shoulder blades and chest area

76

Lean vs. Obese study result in adults

- 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