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Biochemistry > Chapter 19 > Flashcards

Chapter 19 Flashcards

1
Q

In oxidative phosphorylation, energy from ______ and ______ is used to make ATP

A

NADH and FADH2

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2
Q

Where does the energy needed to phosphorylate ADP to ATP come from ?

A

the flow of protons down the electrochemical gradient

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3
Q

In order for the chemiosmotic mechanism to work what must a membrane contain?

A
  • must contain proteins that couple the downhill flow of electrons in the ETC w/ the uphill flow of protons across the membrane
  • must contain a protein that couples the downhill flow of proteins to the phosphorylation of ADP
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4
Q

The 4 distinct compartments of the mitochondria

A

Outer membrane - allows the passage of metabolites
Intermembrane space - higher proton concentration (lower pH)
Inner membrane - relatively impermeable, w/ proton gradient
Matrix - location of CAC, higher pH

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5
Q

_____ and _____ carry electrons from metabolic pathways to the mitochondrial respiratory chain

A

NADH and FADH2

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6
Q

What drives ATP synthase action?

A

The electrochemical potential created by proton efflux

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7
Q

What are the 3 types of electron transfers in oxidative phosphorylation

A
  • direct transfer of e-
  • transfer as a hydrogen atom (H+ + ee)
  • transfer as a hydride ion (H-)
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8
Q

What allows Ubiquinone (Coenzyme Q) to be able to freely diffuse in the inner membrane bilayer (lipid soluble)

A

It’s isoprenoid side chain

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9
Q

What does Complex I do (NADH: ubiquinone oxidoreductase)

A

transfers hydride from NADH and a proton from the matrix to ubiquinone
- has a vectorial proton pump

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10
Q

What does a vectorial proton pump do

A

moves protons in a specific direction from one location to another
- always moves proton from the matrix (negative) to the intermembrane space (positive)

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11
Q

What are inhibitors of complex I

A

Amytal (barbiturate drug)
rotenone (insecticide)
piercidin A (antibiotic)

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12
Q

What does Complex II (succinate dehydrogenase) do?

A

oxidizes succinate and reduces ubiquinone

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13
Q

What is Complex III (Cytochrome Bc1) responsible for?

A

the Q cycle

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14
Q

this part of the mitochondria is porous and allows small molecules and ions to pass

A

outer membrane

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15
Q

this part of the mitochondria is impermeable to most small molecules and ions including H+, it is the location of the ETC complexes

A

inner membrane

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16
Q

this part of the mitochondria has an env similar to cytosol and a higher proton concentration

A

intermembrane space

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17
Q

purpose of iron-sulfur clusters?

A

they do REDOX b/c transition metals can change oxidation state

  • they do one electron transfer reactions
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18
Q

what is a vectorial proton pump?

A

pump that moves protons from the matrix (-) to the inter membrane space (+)

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19
Q

purpose of Heme B in complex II?

A

reduces how often electrons leak out

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20
Q

In what complex does the Q cycle occur

A

Complex III

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21
Q

What compound carries a single electron from the cytochrome bc1 complex (in complex III) to complex IV?

A

Cytochrome C
- absorbs visible light

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22
Q

What does complex IV do?

A

reduces O2 to H20, transfers electrons from reduced cytochrome C to oxygen

  • it is a dimer
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23
Q

These ions are found in subunit II of complex IV and they resemble (physically and functionally) Fe-S clusters

A

CuA ions

24
Q

Name of the supercomplex which contains complexes I,III, IV (II is excluded b/c it needs to be able to feed into the citric acid cycle)

A

Respirasomes

25
Q

What are the two components of the proton motive force

A

chemical potential E - due to difference in concentration of H+ in two regions

Electrical potential E - resulting from separation of charges as protons move across the membrane

26
Q

What two types of radicals are formed during respiration that create ROS?

A

superoxide radical
hydroxyl radical

27
Q

What causes an increase in the generation of ROS?

A

when the flow of electrons in the respiratory chain is slowed down

28
Q

What are the molecules that mediate the toxicities of ROS?

A

Superoxide dismutase (catalyzes the conversion of superoxide and 2H+ into O2 and H202)

Glutathione peroxidase + Glutathione
(convert H202 to H20)

29
Q

What are the two types of chemical uncoupling agents?

A

Hydrophobic weak acids (DNP, FCCP)

Ionophores like valinomycin

30
Q

What blocks complex IV electron transfer to O2 and inhibits respiration and ATP synthesis?

A

Cyanide

31
Q

How do hydrophobic weak acids like DNP and FCCP work as chemical uncoupling agents?

A

they can diffuse across the mitochondrial membrane
- they release protons into the matrix disturbing the proton gradient and therefore disrupting ATP synthase

32
Q

How do Ionophores like VALINOMYCIN work as chemical uncoupling agents?

A

they allow inorganic ions to pass through membranes which disrupts the electrical (charge) gradient due to the dissipation of electrical contribution of the proton motive force

33
Q

What is the role of electron transfer in ATP synthesis?

A

to create a proton gradient

34
Q

What are the two domains of ATP synthase ?

A

Fo and F1
Fo - integral membrane protein, oligomycin sensitive
F1 - peripheral protein and catalytic domain (where the reaction occurs)

35
Q

The free energy required to release ATP is provided by _____?

A

the proton motive force
- the release of ATP is highly endothermic since enzyme binds ATP much stronger than ADP

36
Q

The adenine nucleotide translocase antiporter shuttles ____ out of the matrix while bringing _____ into it

A

ATP4- goes out into the intermembrane space as ADP3- comes in (this is favored by the electrochemical gradient)

37
Q

The phosphate translocase symporter shuttles what two molecules into the matrix ?

A

H+ and H2PO4-

38
Q

NADH dehydrogenase of Complex I can only accept NADH on the _____ side as NADH is impermeable to the membrane

A

matrix side

39
Q

In order to enter the intermembrane space, NADH must be transported in the form of reducing equivalents. What are the possible forms?

A

oxaloacetate to malate —> oxaloacetate in matrix

oxaloacetate to aspartate
aspartate –> oxaloacetate in the intermembrane space

40
Q

The complete oxidation of glucose yields more ATP (32 vs 30) via the _____ shuttle

A

the malate-aspartate shuttle yields more ATP than the Glycerol-3-phosphate shuttle

41
Q

What is the main regulator of oxidative phosphorylation

A

[ADP] which is the substrate
- ADP acts as the acceptor of Pi and the rate of O2 consumption depends on the availability of ADP

42
Q

What are the regulatory proteins of oxidative phosphorylation?

A

IF1 (inhibitor of F1)
HIF-1 (Hypoxia-inducible Factor)

43
Q

How does IF1 inhibit F1

A

it binds to the alpha Beta interface and locks it into place so it cannot rotate around the ATP conformer

44
Q

What conditions favor regulation by IF1

A

low pH and hypoxic conditions (occurs when cells are producing ATP via glycolysis b/c then oxidative phosphorylation is not needed)

-when pH increases, IF1 falls off and F1 is reactivated

45
Q

What conditions cause an increase in HIF-1 expression (and therefore HIF regulation)

A

low oxygen conditions cause an increase in HIF-1 expression

-HIF-1 acts as a transcription factor and decreases the production of ROS

46
Q

Explain what “coupling” means in electron transfer and ATP synthesis

A

coupling refers to the necessary connection b/w mitochondrial ATP synthesis and e- flow through the respiratory chain, neither can proceed without the other

47
Q

Where does the vectorial pump get the energy needed to pump 4H+ out into the intermembrane space ?

A

From the electrical work produced as electrons move through the Fe-S clusters

48
Q

What is the purpose of the Q cycle

A

the transfer of electrons from ubiquinol (QH2) –> cytochrome C

49
Q

What are the two different paths taken by the two electrons in Complex III?

A

one e- goes through Fe-S clusters in the Rieske Center and is then transferred onto the heme group of Cyt C –> Complex IV

the other e- goes to the heme group of Cytochrome B and is then picked up by ubiquinone (Q), Q then gets partially reduced to radial ion Q

50
Q

What is the difference b/w cytochrome C and Ubiquinone (Q) as an electron carrier?

A

Cytochrome C can only bind one electron but ubiquinone can bind 2 e-

51
Q

When does oxidative phosphorylation begin

A

when electrons enter into the respiratory chain

52
Q

What is the importance of ubiquinone having an isoprenoid side chain that makes it lipid soluble

A

lipid soluble means it can diffuse into the inner mitochondrial membrane
– this is important b/c ubiquinone acts as a carrier of protons and electrons throughout complex 1-3

53
Q

What heme group (a.b.c) is covalently bound to cytochrome and what is it attached to?

A

C heme is covalently attached to a CYSTEINE

54
Q

what complex is a citric acid cycle enzyme?

A

Complex II: succinate dehydrogenase

55
Q

What are the three components of Complex III (Cytochrome bc1)

A

cytochrome B, cytochrome C1, Rieske Fe-S protein

Biochemistry (10 decks)

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