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principles of normal function > week 3 citric acid cycle & terminal respiration (revised) > Flashcards

week 3 citric acid cycle & terminal respiration (revised) Flashcards

1
Q

where does the citric acid cycle occur

A
  • mitochondrial matrix
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2
Q

what is the point in the citric acid cycle

A
  • removes electron and passes them on to form NADH and FADH2

- these then pass electrons onto the electron transport chain which creatives a force which drives ATP synthase

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3
Q

how is acetyl coA formed

A
  • pyruvate > acetyl coA , via pyruvate dehydrogenase
  • series of reactions involving decarboxylation of pyruvate, then oxidation, followed by transfer of coA complex
  • decarboxylation step releases two electrons which can pass to oxygen to form ATP through NADH intermediates
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4
Q

what does acetyl coA do

A

allows different intermediates into the citric acid cycle

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5
Q

what is the stucture of pyruvate dehydrogenase

A
  • made up of three subunits called E1, E2 E3

- each subunit catalyses a different part of the reaction to convert pyruvate to acetyl coA

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6
Q

what does subunit E1 of pyruvate dehydrogenase do

A
  • catalyses the first decarboxylation of pyruvate
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7
Q

what does subunit E2 of pyruvate dehydrogenase do

A
  • transfers the acetyl group to coA
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8
Q

what does subunit E3 of pyruvate dehydrogenase do

A
  • recycles the lipoyllysine through the reduction of FAD, which is recycled by passing electrons to NAD
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9
Q

what happens at each turn of the citric acid cycle

A
  • at each turn 2 carbons (acetyl coA) enter
  • 2 different carbons exit the cycle in the form of 2x CO2
  • 3 NADH and 1 FADH2 also leave
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10
Q

how is entry into citric acid cycle controlled

A

pyruvate dehydrogenase is regulated

  • inhibited by ATP if the cell has enough energy
  • activated by ADP + Pi if the cell needs energy
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11
Q

what are the two points of control in the citric acid cycle

A
  1. iso citrate > alpha-ketoglutarate, via isocitrate dehydrogenase
    - inhibited by ATP and NADH
    - activated by ADP
  2. alpha-ketoglutarate > succinyl coA, via alpha-ketoglutarate dehydrogenase
    - inhibited by ATP, NADH and succinyl coA
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12
Q

what does inhibition of isocitrate dehydrogenase in citric acid cycle cause

A
  • citrate build up which shuttles citrate into cytoplasm causing phosphofructokinase to stop glycolysis
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13
Q

what does inhibition of alpha-ketoglutarate dehydrogenase in the citric acid cycle cause

A
  • causes alpha-ketoglutarate build up which switches its use to production of amino acids
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14
Q

what do they mean by saying that the citric acid cycle is amphibolic

A
  • it is anabolic and catabolic
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15
Q

where does terminal respiration (electron transport chain) occur

A
  • on the inner mitochondrial membrane
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16
Q

what electron carrying molecules do you get from glycolysis

A
  • NADH + H+

- ATP

17
Q

what electron carrying molecules do you get from pyruvate > acetyl coA reaction

A
  • NADH + H+
18
Q

what electron carrying molecules do you get from each turn of citric acid cycle

A
  • 3 NADH + H+
  • 1 FADH2
  • 1 GTP
19
Q

what electron carrying molecules do you get from beta oxidation of fatty acids

A
  • 1 NADH + H+

- 1 FADH2

20
Q

what is the job of the glycerol phosphate shuffle

A
  • NADH can’t get through outer membrane to electron transport chain so FADH2 passes the electrons on for it, this is the glycerol phosphate shuffle
  • majority of NADH and FADH2 is formed in the mitochondrial matrix, it has to be there to be oxidised, but some of NADH is formed in the cytoplasm so FADH2 transports its electrons for it since it can’t cross
21
Q

what are the steps in the glycerol phosphate shuffle

A
  • NADH + H+ > NAD+ as it loses electrons
  • dihydroxy acetone phosphate becomes glycerol 3 phosphate as it holds the electrons from NADH + H+
  • glycerol 3 phosphate passes the electrons to FAD which becomes FADH2 at the outer mito. membrane
  • FADH2 passes electrons to electrons transport chain on the inner mitochondrial membrane
22
Q

what is the downside to the glycerol phosphate shuffle

A
  • oxidation of FADH2 in electron transport chain generates, per mol, less ATP than NADH
  • this energetic ‘price’ is paid for using cytosolic reduced co-substrates in terminal respiration
23
Q

what is the order of the complexes in the electron transport chain

A

complex 1 = NADH-Q oxidoreductase
complex 2 = succinate-Q reductase
- then ubiquinone/Q pool (but this isn’t a complex, becomes ubiquinol once it has electrons passed to it)
complex 3 = Q cytochrome c oxidoreductase
complex 4 = cytochrome c oxidase

24
Q

what happens at complex 1 (NADH-Q oxidoreductase) of the electron transport chain

A
  • oxidises NADH
  • passes the electrons to ubiquinone which becomes ubiquinol (QH2)
  • utilises Fe-S centres and FVM
  • pumps H+ into intermembrane space
25
Q

what happens at complex 2 (succinate-Q reductase) of the electron transport chain

A
  • oxidises FADH2
  • passes electrons to ubiquinone becoming ubiquinol (QH2)
  • utilises Fe-S centres to channel electrons
  • (doesn’t pump H+)
26
Q

what happens at complex 3 (Q-cytochrome c oxidoreductase) of the electron transport chain

A
  • takes electrons from ubiquinol and passes them to cytochrome c
  • pumps H+ into the inter membrane space
27
Q

what happens at complex 4 (cytochrome c oxidase) of the electron transport chain

A
  • takes electrons from cytochrome c and passes them to O2 (O2 > H2O)
  • electrons channeled through Fe-Cu centre
  • pumps H+ into the inter membrane space
28
Q

what is the electron motive force

A
  • the concentration gradient generated by the complexes of the electron transport chain pumping H+ into the intermembrane space
  • high [H+] in intermembrane space
29
Q

what drives ATP synthase

A
  • the electron motive force

- (the concentration gradient created by the electron transport chain)

30
Q

what is chemiosmosis

A
  • the electrons pass through the complexes of the electron transport chain and at the same time H+ is pumped into the intermembrane space, this is called chemiosmosis
31
Q

how does ATP synthase work

A
  • H+ flows down its concentration gradient, through ATPase to get back into the matrix
  • as this happens the energy stored in the gradient is used to convert ADP + Pi to ATP
32
Q

what is the structure of ATP synthase

A

2 parts
F0 - membrane bound proton conducting unit (10 subunits)
F1 - protrudes into mitochondrial matrix, acts as catalyst for ATP synthase
- ADP + Pi enters beta subunit of F1
- rotation of F0 cylinder and conformation changes in beta subunits of F1
- conformational changes catalyse ADP > ATP and release ATP

33
Q

what is the stoichiometry of oxidative phosphorylation

A
  • complexes 1,3,4 of electron transport chain move total of 8 H+ from matrix to outside membrane
  • ATP synthase produces 1 ATP for every 3 H+ moved back into matrix
  • approx. 2.5 and 1.5 mol of ATP are generated per mol of NADH and FADH2 respectively
  • overall oxidative phosphorylation produces 32 ATP (30 if using cytosolic NADH)
34
Q

what is coupling and uncoupling of electron transport chain and ATP synthesis

A
  • electron transport chain and ATP synthesis are said to be coupled
  • if the inner mitochondrial membrane became permeable to H+ then you would not get the proton gradient, electron transport would still occur and O2>H2O, but no ATP would be made, so process would be uncoupled
  • energy released from electrons would be released as heat instead of making ATP
35
Q

what is malignant hyperthermia

A
  • occurs when the electron transport chain and ATP synthesis processes become uncoupled
  • caused by leaky mitochondrial membrane
  • brown fat in babies

principles of normal function (15 decks)

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