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Fundamentals Of Life Science > TCA cycle, ETC, and ATP synthesis > Flashcards

TCA cycle, ETC, and ATP synthesis Flashcards

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1
Q

Where does the TCA cycle occur?

A

in the matrix of the mitochondria

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2
Q

Once pyruvate is produced, what happens?

A

It is transported into the mitochondria converted into acetyl CoA and enters into the TCA cycle

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3
Q

What is the reaction converting pyruvate to acetyl-CoA?

A

Pyruvate + HSCoA + NAD+ —-> Acetyl CoA + CO2 + NADH

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4
Q

Why is pyruvate to acetyl CoA an irreversible reaction?

A

Since ΔG is very -tve

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5
Q

What is the TCA cycle?

A

Process by which pyruvate that has been converted to Acetyl CoA has its acetyl group oxidatively decarboxylated to produce CO2, NADH, ATP and ubiquinol

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6
Q

What is oxidative phosphorylation?

A

The process by which the respiratory electron transport chain is coupled with ATP synthesis

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7
Q

What is the final electron acceptor in the ETC?

A

Oxygen

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8
Q

What enzyme is required in the reaction of pyruvate to CoA?

A

Pyruvate Dehydrogenase

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9
Q

What is the role of Coenzyme A?

A

activates acetyl groups so they can be readily transferred to metabolites

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10
Q

What are the three enzymes found in the pyruvate dehydrogenase complex and what are their roles?

A

E1 pyruvate dehydrogenase= oxidative carboxylation of pyruvate
E2 dihydrolipoyl transacetylase= transfer of acetyl group to CoA
E3 dihydrolipoyl dehydrogenase= regeneration of lost lipoamide

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11
Q

What is the structure of pyruvate dehydrogenase?

A
  • inner core =copies of E2 and E3

- outer shell = copies of E1 and E2

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12
Q

What is the order of the carbon containing molecules in the TCA cycle?

A 
Acetyl CoA (C2)
citrate (C6) 
cis-aconiatate (C6) 
isocitrate (C6) 
α-keto glutarate (C5) 
succinyl-CoA (C4) 
succinate (C4) 
fumigate (C4) 
malate (C4) 
oxalo-acetate (C
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13
Q

What are the overall reactions of the TCA cycle?

A

Acetyl CoA —> CoA + 2CO2
3NAD+ —> 3NADH
FAD —> FADH2
GDP + Pi —> GTP (substrate level phosphorylation)

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14
Q

What is the equation for Gibbs free energy of electron transfer?

A

ΔG = -nF ΔEh

n=no. of electrons
F= faraday’s constant = 96500C.mol^-1

ΔEh must be positive for a spontaneous reaction

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15
Q

Does PH alter mid-point potentials?

A

yes

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16
Q

When does Eh =Em

A

when [red] = [ox]

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17
Q

What are the steps of oxidative phosphorylation?

A
  1. NADH is oxidised to NAD+ and the 2 electrons pass down complex I where they meet ubquinone
  2. ubiquinone is reduced to ubiquinol
  3. ubiquinol carries electrons to complex III
  4. electrons flow through complex III to cytochrome C
  5. cytochrome C carries electrons to complex IV which reduces complex IV and the electrons are transferred to oxygen (terminal electron acceptor)
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18
Q

What is the energy used for that is released from these electron transfer events?

A

to pump protons (for every 2 electrons that flow through complex I, 4 protons are pumped from the matrix to the outside (overall 10 protons pumped across per 2 electrons) to create a PH and charge gradient

19
Q

What is the reduced form of pyruvate?

A

lactate

20
Q

What is the oxidised form of succinate?

A

fumigate

21
Q

What is complex II also known as?

A

mitochondrial succinate dehydrogenase

22
Q

What is the only membrane-bound enzyme in the TCA cycle?

A

mitochondrial succinate dehydrogenase (complex 2)

23
Q

What is complex II part of?

A

ETC and TCA cycle (catalyses succinate turning into fumerate)

24
Q

What stops the TCA cycle if ATP is not required?

A

complex II

25
Q

what is an alternate route into the TCA?

A

complex II (lower energy entry) every time succinate is being converted into fumigate in the TCA 2 electrons enter the TCA cycle via complex II

26
Q

If you stop ATP synthesis using oligomyocin what do you also stop?

A

ETC

27
Q

How do uncouplers work?

A

by increasing the permeability of the membrane to protons

28
Q

What are the effects of an uncoupler?

A

-relief from respiratory control: acceleration of respiratory rate and inhibition of ATP synthesis

29
Q

What is the ΔG equation for ions?

A

ΔG = -mF Δp

m= amount of charge (no. of ions xF)
F=faraday constant
Δp= electrochemical potential across the membrane

30
Q

What is the structure of ATP synthase?

A

made up of starter Fragment (F1) and rotator fragment (F0)

31
Q

What is the yeast F0 rotor formed of?

A

10 helical hairpin proteins

-on the outside helix of each hairpin an aspartic acid which spins the ATP synthase

32
Q

What happens when a proton moves through ATP synthase?

A
  1. protein moves halfway across the membrane where it meets an aspartic acid on the C ring, the only way the proton can get through is by turning the wheel by neutralising the aspartic acid so it can move through the lipid bilayer and when the aspartic acid reaches the channel again it releases the proton so it can travel through the channel
33
Q

What happens when the C ring spins around?

A

It drives the gamma subunit to spin around, catalysing the unfavourable reaction of ATP synthesis

34
Q

How does ATP get synthesised?

A
  • there are 3 active sites in ATP synthase, one has ATP bound, one has ADP and Pi bound and the other is empty
  • ADP and Pi bind to empty active site
  • gamma subunit rotates, activating ADP and Pi
  • gamma subunit rotates further and unbinds already formed ATP
35
Q

How many ATP are produced for each 360 degree rotation of the gamma subunit?

A

3

36
Q

What enzyme us used to catalyse the reaction between citrate and cis-aconitate?

A

Aconitase

37
Q

What enzyme us used to catalyse the reaction between Cis-aconitate and Isocitrate?

A

aconitase

38
Q

What enzyme us used to catalyse the reaction between Isocitrate and alpha-keto-glutarate?

A

Isocitrate dehydrogenase

39
Q

What enzyme us used to catalyse the reaction between alpha-keto-glutarate and succinyl-CoA?

A

alpha-keto-glutarate dehydrogenase complex

40
Q

What enzyme us used to catalyse the reaction between Succinyl-CoA and Succinate?

A

Succinyl-CoA synthase

41
Q

What enzyme us used to catalyse the reaction between Succinate and fumerate?

A

Succinate dehydrogenase complex II

42
Q

What enzyme us used to catalyse the reaction between Fumerate and malate?

A

fumerase

43
Q

What enzyme us used to catalyse the reaction between malate and oxaloacetate?

A

Malate dehydrogenase

44
Q

What enzyme us used to catalyse the reaction between oxaloacetate and citrate?

A

Citrate synthase

Fundamentals Of Life Science (26 decks)

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