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Biochem 2 > ETC > Flashcards

ETC Flashcards

1
Q

What do reducing equivalents do for ETC?

A

-add e- to ETC but not to build molecules = for energy
-pass through oxidation and reduction reactions to get energy

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2
Q

Where does the ETC occur?

A

-occurs in matrix and inner mito membrane

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3
Q

List examples of electron carriers

A

-NAD and FAD: organic carries
-Quinones: lipid carriers
-Hemes and iron-sulfur clusters: biometallic carriers

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4
Q

What are mitochondrial shuttles?

A

-transport systems used to help compounds cross the mitochondrial inner membrane
-move NADH equivalents across membrane to get e- to ETC

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5
Q

Name two of the mitochondrial shuttles used in ETC?

A

-glycerophosphate shuttle
-aspartate-malate shuttle

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6
Q

In terms of permeability, how are the outer and inner mitochondrial membranes different?

A

-outer mem is leaky
-inner mem is impermeable

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7
Q

What are the steps to the dehydrogenase mito shuttle?

A

NADH (from glycolysis) becomes NAD+ -> DHAP via GAP dehydrogenase becomes GAP -> GAP goes back to DHAP when they transfer e- to FAD on the other side of the membrane -> FAD becomes FADH2 via dehydrogenase

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8
Q

What are the steps for the malate/aspartate shuttle?

A

NADH becomes NAD+ via malate dehydrogenase -> malate enters matrix and exchanges with a-ketoglutarate (antiporter) -> malate becomes oxaloacetate in TCA via NAD+ and malate dehydrogenase -> oxaloacetate becomes aspartate and glutamate becomes a-ketoglutarate via transamination -> aspartate leaves matrix exchanges with glutamate (antiporter) -> aspartate and ketoglutarate do transamination to glutamate and oxaloacetate

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9
Q

Does the a-ketoglutarate and glutamate circuit in the malate/aspartate shuttle require an enzyme?

A

-no, just a transamination reaction

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10
Q

What occurs in Complex 1?

A

-NADH dehydrogenase
-site of NADH oxidation
-pumps 4H+ out of matrix
-e- are transferred to Q
-Q -> QH2

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11
Q

What are quinones?

A

a ring structure (the quinone) and a hydrophobic tail

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12
Q

What are some different forms of quinone?

A

quinone + 1e- + 1H = semiquinone
semiquinone +1e- +1H = hydroquinone

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13
Q

What occurs in Complex 2?

A

-succinate dehydrogenase
-generates a reduced ubiquinone (QH2)
-no protons pumped out

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14
Q

What occurs in Complex 3?

A

-cytochrome c reductase
-e- transferred to cytochrome c
-1e- at a time
-4H+ pumped out per 1 QH2

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15
Q

What is a Q pool?

A

-combination of oxidized and reduced forms of ubiquinone found in mito membrane

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16
Q

characteristics cytochrome c

A

-soluble e- carrier
-receives e- from complex 3
-has heme to carry 1e-

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17
Q

what is inside a cytochrome protein?

A

a heme

18
Q

What is the issue with electron transport?

A

-ETC is leaky
-QH2 is 2e- carrier
-cyt c is a 1e- carrier
-radicals are bad

19
Q

What is the Q cycle?

A

-the sequence of transferring e- from QH2 to cyt c without release radicals to the rest of the cell

20
Q

What is the reaction equation for Q cycle step 1?

A

QH2 + Q + cyt c (oxidized) -> Q + Q.- + 2Hp+ + cyt c (reduced)

21
Q

What is the reaction equation for Q cycle step 2?

A

QH2 + Q.- + 2Hn+ + cyt c (oxidized) -> Q + 2Hp+ + QH2 + cyt c (reduced)

22
Q

What is the net equation for the Q cycle?

A

QH2 + Q + 2 cyt c (oxidized) + 2Hn+ -> Q + 2 cyt c (reduced) + 4Hp+

23
Q

What are the steps for Q cycle part 1?

A

QH2 enters cytochrome b -> 2H+ leave -> 1 e- attaches to 2Fe-2S -> 1e- gets passed to heme in cyt 1 -> cyt c leaves -> the Q leaves the cytochrome but stays in the lipid mem -> the other 1e- stays with the Q as a radical inside cyt b

24
Q

What are the steps for Q cycle part 2?

A

similar as part 1
QH2 enters cyt b -> 2H+ leave -> 1e- leaves Q to 2Fe-2S and then heme and then cyt c leaves -> 1 q leaves cyt b ->the other 1e- with the Q attaches to the initial Q radical and bring in 2H+ to bind and create QH2

25
Q

What occurs in complex 4?

A

-cytochrome c oxidase
-takes 4e- from cyt c
-pumps 2H+ out of mito matrix
-reduces O2 and H2O
-uses other e- carriers
-O2 is terminal electron acceptor

26
Q

What is a respirasome?

A

-aggregated supercomplex with complex 1, 3 and 4
-assists with substrate channeling

27
Q

What is ATP synthase?

A

-aka F0/F1 ATPase
-multisubunit
-responsible for ATP production
-use electrochemical energy and chemical gradient for: ADP+Pi->ATP

28
Q

What are uncouplers?

A

-they interfere with electron transport
-generate heat instead of ATP

29
Q

What is the mechanism of ATP synthase?

A

-protons move between a and subunits of F0 complex
-powered by PMF
-subunit c rotates
-gamma and epsilon subunits also move through hexamer of a and b subunits
-conformation change
-binds ADP with Pi

30
Q

How does ATP Synthase rotate?

A

-three subunits
-each have three states: open, loose binding, tight binding
-open: empty
-loose: ADP+Pi enter
-tight: ATP created
-open: ATP kicked out

31
Q

What is the point of the rotation of ATP Synthase?

A

-the product and enzyme form is very stable and favourable = ATP wants to stay in the enzyme
-by twisting to open position, ATP is forced out
-aka rotational catalysis

32
Q

How was the rotation of ATP Synthase proved?

A

-they tagged the rotating part with a fluorescent actin filament and watched it move

33
Q

What is the proton motive force?

A

-electrochem potential from uneven distribution of e- across mito matrix
-involves chemical and electrical potential

34
Q

What is chemical potential?

A

-the high concentration of protons on outside of mem compared to the inside
-expressed as ΔpH

35
Q

What is electrical potential?

A

-added positive charge that accumulates outside the mem
-measured V or mV
-voltage drop across mem

36
Q

What is the equation for Gibbs Free Energy in correlation to membrane potential?

A

ΔG = nℱΔΨm
-F = Faraday’s constant

37
Q

What are the 5 types of ATPases?

A

-F
-A
-V
-E
-P

38
Q

How do ATPases perform their function in reverse?

A

use ATAP hydrolysis

39
Q

What is an ATP:ADP Translocase?

A

-enzyme; antiporter
-transports ATP from mito
-in exchange for ADP
-transmem integral protein with 6 a helices
-conformational change
-driven by [ ] difference between ATP and ADP

40
Q

What is phosphate translocase?

A

-enzyme; symporter
-replaces PO4- lost as ATP
-driven by PMF

Biochem 2 (7 decks)

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