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MBOD week 11 > ATP Synthase > Flashcards

ATP Synthase Flashcards

1
Q

What does treatment of the mitochondrial membrane with urea do?

A

uncouples ATP synthase by causing dissociation of the F1 portion

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2
Q

What part of ATP synthase contains the catalytic subunit?

A

F1

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3
Q

What is the Fo subunit of ATP synthase?

A
  • membrane bound portion

- contains the proton channel

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4
Q

What inhibits the Fo subunit?

A

Oligomycin

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5
Q

Can O2 still be reduced to H2O when F1 is removed from ATPase? Why or why not?

A

Yes, Removing F1 does not inhibit the reducing abilities of the ETC complexes

note: ATP is NOT being synthesized if not F1 is present so respiration is UNCOUPLED

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6
Q

How do uncouplers work?

A
  • They get protonated in the relatively acidic intermembrane space where protons are being pumped
  • Pronation neutralizes their charge allowing them to cross the inner membrane
  • once in the matrix they loose the proton in the relatively basic environment
  • The net affect is that protons are moving backwards
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7
Q

T or F: the general leakyness of the mitochondrial membrane causes uncoupling.

A

True

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8
Q

Give two examples of common uncouplers of the mitochondrial membrane.

A
  1. CCCP
  2. DNP
  3. FCCP
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9
Q

T or F: if no electrons flow, then no ATP can be made.

A

True

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10
Q

T or F: if no ATP is made then electrons cannot flow.

A

True

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11
Q

Why can electrons not flow in a normal cell if no ATP is being made?

A
  • The proton gradient builds up to be so large that even the energy released by oxidation of NADH will not be enough to pump protons against such a large gradient
  • During ATP synthesis by ATPase protons are pumped back to the matrix
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12
Q

In the presence of an uncoupling agent no ATP is made yet electrons continue to flow. Explain this.

A
  • The proton gradient is reduced by the uncoupling agents that bring the protons back to the matrix side.
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13
Q

What is the respiratory control ratio, and what should it be in good preparations of isolated mitrochondria?

A
  • Ratio of State 3 repiration to state 4 respiration

- Should be 5-6

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14
Q

T or F: uncouplers allow the mitochondria to resume to state 3 respiration even in the absence of ADP and Pi.

A

True, state 3 respiration will only stop at this point when the cell runs out of O2

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15
Q

What structural changes would you expect to see in a mitochondria if a uncoupling agent had been added.

A
  • State 3 respiration will happen

- Large periplasmic space, Condensed Matrix

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16
Q

Why would a bear want to uncouple its membrane in the winter, and what protein would be used to do this?

A
  • Uncoupling generates heat because the cell is working to build enough to shut of TCA and ETC but never does
  • The end result of this continued cycle is heat production
  • The bear would use UCP1
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17
Q

How does UCP1 work?

A
  • Transports Fatty acid anions across the INNER mitochondrial membrane FROM MATRIX TO INTERMEMBRANE SPACE in exchange for Cl- or OH-
  • The Fatty acids get protonated as soon as they cross the membrane
  • Since they are neutral and lipophilic they can cross back over to the MATRIX without a transporter carrying the H+ with them
18
Q

What did the experiement of Racker and Walther with light activated proton pumps show.

A

Exp. Recap.
- They made a vesicle that with bacteriohodopsin (light driven pump) that pumped in protons in when light was on, the only other thing on the vesicle was ATP synthase

  • ATP was made when the light shined, since ATP synthase and Bacteriohodopsin were the only things present it proved NOTHING BESIDES ATP SYNTHASE AND A PROTON GRADIENT was need to make ATP.
19
Q

What does the c subunit of ATP synthase consist of?

A
  • 2 helices with an aspartate in the middle, which is REQUIRED for the proton channel
20
Q

Would a substitution of glutamate for aspartate at the c subunit allow for continued function of ATP syntase?

A

Yes, what’s needed in that position is a carboxylate group that can easily grab and release a proton

21
Q

How does DCCD (dicyclohexyl carboiimide) work?

A
  • Reacts with c subunit blocking proton flow via the channel
22
Q

Does ATP synthase rely on the mitochondrial genome to function?

A

Yes, Fo subunits are coded for by the mitochondrial genome

23
Q

T or F: the F1 particle contributes to the long stalk.

A

True

24
Q

T or F: oligomycin binds to the oligomycin sensitivity conferring protein.

A

FALSE

25
Q

T or F: the gamma subunit is symmetrical

A

False, its asymmetry is very important to its conformational control over the BETA subunits

26
Q

Summarize Paul Boyers 3 postulates of ATP synthase binding.

A
  1. Proton gradient is used to RELEASE ATP not to form it (it forms spontaneously by super tight binding)
  2. the 3 catalytic sites have unique conformations that are interconvertable (i.e. each Beta can exist in 1 of 3 states)
  3. Conformational changes at the three sites are driven by rotation of gamma relative to the alpha-beta ball
27
Q

How did Paul Boyer show that ATP could be made without a proton gradient?

A
  • add ADP, Pi and H2O with O-18 isotope to ATP synthase with no proton gradient
  • O-18 got incorporated Pi
  • The only way this could happen if ATP had been made an rehydrolyzed
28
Q

How was it proven that gamma spins and not alpha and beta?

A

They tied alpha and beta down to glass to make them immobile then put fluorescent actin on the gamma unit and the actin could be seen spinning

29
Q

How many protons are pumped across the membrane at each complex in the ETC?

A

Values given per electon pair

  • Complex I - 4 H+
  • Complex II - 0
  • Complex III - 4 H+ (2 for each turn of Q cycle)
  • Complex IV - 2 H+ (4 protons for complete reduction of O2 to water)
30
Q

About how many protons are consumed per ATP synthesized?

A

4

31
Q

How many ATPs are made per revolution of F1?

A

3

32
Q

What is the elevator model, and what is the sequence of events?

A
  1. Protons pass through subunit a to aspartate on one of 10-12 subunit c’s
  2. 1 H+ binding causes another to be released resulting in rotation of Fo
  3. Fo is attached to gamma so 3-4 protons binding causes 1/3 of cycle to be completed
  4. This results in 1 ATP being produced
33
Q

What happens if a subunit is mutated or if 1 of the c subunits is mutated?

A

The whole ATP synthase ceases to work

- this suggests c moves relative to a

34
Q

What forms the rotor portion of ATP synthase?

A

C subunit ring bound to epsilon and gamma

35
Q

What makes up the stator part of ATP synthase?

A

a, b, alph, beta, and delta subunits

36
Q

Why would ATP synthase line up on the edges of cristae in rows of dimers?

A

The proton gradient is more concentrated in these creases

37
Q

How many protons are pumped from 1 NADH, how many ATPs does this lead to?

A

4 at complex I
4 at complex III
2 at complex IV

Total = 10 H+ per NADH (~2.5 ATP per NADH)

38
Q

How many protons are pumped from 1 FADH2, how many ATPs does this lead to?

A

4 at complex III
2 at complex IV
*Remember complex II produces the FADH2 and at this point its already passed complex 1 so you miss out on those protons

Total = 6 H+ per FADH2 (~1.5 ATP per NADH)

39
Q

How many NADH and FADH2 molecules are produced during aerobic respiration, how much ATP does this produce?

A

Per GLUCOSE

Glycolysis = 2 NADH
TCA = 8 NADH. 2 FADH2 (4 for each pyr.)

25 ATP from NADH
3 ATP from FADH2
28 ATP total

40
Q

How many ATP are produced from aerobic respiration?

A

28 from OxPhos
4 from substrate level Phos.
32 ATP total

41
Q

How is ATP moved out of the mitochondria?

A

ATP/ADP carrier

MBOD week 11 (11 decks)

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