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MBB161 > Johnson (Cellular Respiration) > Flashcards

Johnson (Cellular Respiration) Flashcards

1
Q

What is the difference between anabolism and catabolism?

A
  • anabolism = making stuff, mainly endergonic (+ΔG)
  • catabolism = breaking stuff down, mainly exergonic
    (-ΔG)
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2
Q

What is the relationship between catabolism and anabolism?

A
  • catabolism provides energy for anabolism
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3
Q

What is cellular respiration?

A
  • catabolic breakdown of red C derived from fats and sugars to gain energy
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4
Q

What is glycolysis?

A
  • central ATP prod pathway
  • in cytosol
  • involves 10 enzymatic reactions
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5
Q

Where do heterotrophs obtain energy from?

A
  • ox red C sources, eg. sugars and fats
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6
Q

Why are reactions in respiration carried out stepwise?

A
  • to release energy in controlled way, so it can be captured and stored in activated carrier molecules
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7
Q

How does ox of C compounds provides energy?

A
  • C-H bonds less stable than C-O and C=O

- so energy yielded to env when C-H bonds replaced by them –> so ox of C provides energy

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8
Q

Which part of respiration is common to animals, plants and many bacteria?

A
  • glycolysis
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9
Q

To what extent is O involved in glycolysis?

A
  • not req

- but involved as e-s removed from C to NADH

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10
Q

What is the net gain from glycolysis?

A
  • 2 ATP
  • 2 NADH
  • 2 pyruvate
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11
Q

What are the 10 steps of glycolysis?

A

1) Glucose phosphorylation
2) Isomerisation to fructose
3) 2nd phosphorylation
4) Cleavage
5) Conversion of DHAP
6) Oxidation of GADP
7) 1st phosphate transfer to ADP
8) Isomerisation to 2-phosphoglycerate
9) Removal of water
10) 2nd phosphate transfer to ADP

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12
Q

What occurs during glucose phosphorylation, and what is the role of the negative charge on the Pi? (1st step glycolysis)

A
  • glucose to glucose-6-phosphate
  • by hexokinase
  • req ATP input
  • negative charge on Pi traps G6P inside cell
  • also keeps glucose conc low, promoting uptake via glucose transporter proteins
  • charge destabilises molecule, facilitating further metabolism
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13
Q

Why is ATP less stable than ADP + Pi?

A
  • negative phosphate charges repel
  • lower entropy
  • less interactions w/ water
  • free Pi stabilised by resonance structures, not poss when bound to ATP
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14
Q

In terms of equilibrium, which is favoured, ATP or ADP + Pi?

A
  • ADP + Pi greatly favoured
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15
Q

What happens to reaction in terms of ATP prod, depending on ΔG value?

A
  • at equilibrium reaction has no capacity to do work
  • when ΔG-ve, hydrolysis of ATP favourable under cellular conditions
  • when ΔG+ve, synthesis of ATP req energy under cellular conditions
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16
Q

Why is there no such thing as a high energy bond, what is really meant?

A
  • simply extent conc of products to reactants (Γ) displaced from equilibrium
  • this defines capacity of reaction to do work
  • not attribute of any single component
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17
Q

What is req for 2 reactions to be coupled?

A
  • must share 1 or more intermediates
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18
Q

What is the ΔG of coupled reactions?

A
  • sum of 2 individual reactions
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19
Q

What occurs during isomerisation to fructose, what kind of sugars are converted and is it reversible? (2nd step glycolysis)

A
  • G6P to F6P
  • by phosphoglucose isomerase
  • aldose sugar converted to ketose sugar (necessary for step 4)
  • readily reversible under cellular conditions
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20
Q

What occurs during 2nd phosphorylation, and how is entry of sugars into glycolysis controlled at this step? (3rd step glycolysis)

A
  • F6P to fructose-1,6-bisphosphate
  • phosphofructokinase
  • req ATP input
  • 2nd Pi further destabilises sugar, promoting cleavage in step 4
  • entry of sugars into glycolysis controlled via allosteric reg of phosphofructokinase by ATP levels in cell, ATP binds to enzyme downregulating it
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21
Q

What occurs during cleavage? (4th step glycolysis)

A
  • F1,6BP to DHAP + GADP
  • by aldolase
  • only GADP can progress through glycolysis
  • isomerisation to fructose ensures 3:3 split of C, rather than 2:4 which would req 2 separate pathways to metabolise
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22
Q

What occurs during conversion of DHAP? (5th step glycolysis)

A
  • DHAP –> GADP

- K greatly in favour of DHAP, but reaction proceeds as GADP constantly removed by glycolysis pathway

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23
Q

What occurs during oxidation of GADP? (6th step glycolysis)

A
  • GADP to 1,3-bisphosphoglycerate (compound w/ high phosphoryl transfer pot)
  • by glyceraldehyde-3-phosphate dehydrogenase
  • NADH formed
  • 1st energy gen step
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24
Q

What are the common activated carrier molecules?

A
  • NADH
  • FAD/FADH2
  • CoASH
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25
Q

Why is ox coupled to phosphorylation by enzyme linked intermediate during oxidation of GADP? (6th step glycolysis)

A
  • if 2 processes weren’t coupled, activation energy means it wouldn’t occur at biologically sig rate
  • coupling via enzyme linked thioester intermediate allows first -ΔG process to drive 2nd +Δ process
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26
Q

What occurs during 1st phosphate transfer to ADP? (7th step glycolysis)

A
  • 1,3-BPG to 3-phosphoglycerate
  • Pi transfer from 1,3-BPG to ADP, forming ATP
  • by phosphoglycerate kinase
  • substrate level phosphorylation
  • 2nd energy gen step
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27
Q

What is substrate level phosphorylation?

A
  • transfer of Pi from compound w/ high phosphoryl transfer pot to ADP
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28
Q

What is oxidative phosphorylation

A
  • transfer of Pi from compound w/ low phosphoryl transfer pot to ADP
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29
Q

What occurs during isomerisation to 2-phosphoglycerate? (8th step glycolysis)

A
  • 3-phosphoglycerate to 2-phosphoglycerate
  • by phosphoglycerate mutase
  • remaining phosphodiester linkage, w/ relatively low phosphoryl transfer pot, transferred from C3 to C2
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30
Q

What occurs during removal of water? (9th step glycolysis)

A
  • 2-phosphoglycerate to phosphoenolpyruvate

- by enolase

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31
Q

How is high-phosphoryl transfer pot compound made from low pot compound, where did energy come from? (9th step glycolysis - removal of water)

A
  • 2-phosphoglycerate and PEP contain small amount of pot metabolic energy w/ respect to decomposition to Pi, CO2 and H2O
  • enolase reaction rearranges substrates into form from which more of pot energy can be released upon hydrolysis
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32
Q

What occurs during 2nd phosphate transfer to ADP? (10th step glycolysis)

A
  • phosphoenolpyruvate to pyruvate
  • by pyruvate kinase
  • transfer of phosphate group to ATP
  • 3rd energy gen step
  • substrate level phosphorylation
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33
Q

What happens to ATP and NADH at end of glycolysis?

A
  • ATP used directly in cyto to power cellular processes

- NADH imported into mito for OP to gen more ATP

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34
Q

What is the Warburg effect?

A
  • tumours have enhanced glycolysis and glucose uptake

- metabolise glucose through to lactate even when O2 present

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35
Q

Why is the Warburg effect an advantage to cancer?

A
  • acidifies env, facilitating tumour invasion of surrounding tissue
  • grow faster than surrounding blood vessels so O2 conc decreases, this doesn’t matter if using glycolysis for ATP
  • excess glucose activates pentose phosphate pathway, gen NADPH for biosynthesis and enhanced growth
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36
Q

How can Warburg effect be used to monitor cancer cells?

A
  • by using FDG, a non-metabolisable glucose analogue which binds to hexokinase, tumours can be detected by positron emission tomography and CAT scanning
  • FDG infused into patients blood, reveals tumours location and accum in kidneys/bladder
  • tumours disappeared after 5wks treatment
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37
Q

What is fermentation?

A
  • making ATP w/o O2
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38
Q

What happens in absence of O2 at end of glycolysis?

A
  • no further ox of pyruvate

- won’t proceed due to redox imbalance

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39
Q

How does NAD+ regen to restore redox imbalance and allow glycolysis to continue w/o O2

A
  • NADH accum due to inhibition of e- transport, causing NAD+ shortage, inhibiting glycolysis
  • to avoid this, NADH red pyruvate to lactate or ethanol, which can be excreted from cell
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40
Q

What occurs during fermentation in muscle tissue?

A
  • pyruvate converted to lactate
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41
Q

What occurs during fermentation in yeast and bacteria?

A
  • pyruvate converted to acetaldehyde (2H+ –> 2CO2)

- acetaldehyde converted to ethanol and NAD+ regen in this step

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42
Q

What happens to pyruvate under aerobic conditions?

A
  • pyruvate ox to acetyl CoA and CO2 by pyruvate dehydrogenase complex in mito matrix
  • contains 3 diff enzymes and 60 polypeptide chains
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43
Q

What is the role of CoASH?

A
  • carries acetyl group via thioester linkage
  • hydrolysis of linkage -ΔG under cellular conditions
  • can be coupled to +ΔG reactions, eg. 1st step of citric acid cycle
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44
Q

What are 3 steps of the Link Reaction?

A

1) decarboxylation of pyruvate
2) oxidation of hydroxyethyl group
3) red of NAD+

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45
Q

What occurs during decarboxylation of pyruvate? (1st step link reaction)

A
  • CO2 removed from pyruvate
  • by pyruvate decarboxylase (PD)
  • resulting hydroxyethyl group binds to thiamine pyrophosphate (TPP), a co-factor of PD
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46
Q

What occurs during oxidation of hydroxyethyl group? (2nd step link reaction)

A
  • hydroxyethyl group to acetyl group
  • transferred to lipoamide
  • ox is by dihydrolipoyl transacetylase
  • acetyl group then transferred to CoASH forming acetyl CoA and red lipoamide
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47
Q

What occurs during red of NAD+? (3rd step link reaction)

A
  • red lipoamide ox by dihydrolipoyl dehydrogenase

- FADH2 formed, used to red NAD+ to NADH

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48
Q

What does NADH stand for?

A
  • nicotinamide adenine dinucleotide
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49
Q

What does FAD stand for?

A
  • flavin adenine di-nucleotide
50
Q

What is FAD capable of?

A
  • carrying 2e-s, but binds 2H+ when red
51
Q

What is the role of pyruvate dehydrogenase complex (PDH) in the link reaction?

A
  • PDH organisation min distance highly reactive substrates have to travel between active sites
  • this substrate channeling increases reaction rate and decreases unwanted side reactions
52
Q

How are FAs used as a source of acetyl CoA?

A
  • fats more red than sugars, so gen more energy when ox
  • lipases breakdown fats into glycerol and FAs
  • glycerol enters glycolysis by conversion to DHAP
  • FAs transported back to mito
53
Q

What occurs during β ox of FAs?

A
  • FAs activated via linkage to CoASH, req ATP –> AMP + PPi), and transported back into mito
  • 4 enzymes ox FA CoA 1 C unit at a time
  • oxidations (-ΔG) coupled to gen of NADH and FADH2 (+ΔG)
54
Q

Why is the Krebs cycle necessary? (biochemical logic)

A
  • ox of acetate to 2CO2 req C-C bond cleavage
  • C-C cleavage usually between α and β Cs adjacent to carbonyl group OR cleavage of α-hydroxyketone
  • neither poss w/ acetate, as no β C and 2nd method would req +ΔG hydroxylation
  • by condensing acetyl CoA w/ oxalacetate to form citrate, gen β-cleavage site, allowing full ox
55
Q

What are the 8 steps in the citric acid cycle?

A

1) citrate formation
2) citrate isomerisation
3) 1st decarboxylation
4) 2nd decarboxylation
5) ATP formation
6) succinate ox
7) fumarate hydration
8) malate ox

56
Q

What occurs during citrate formation? (1st step citric acid cycle)

A
  • citrate synthase removes H+ from methyl group on acetyl CoA
  • forming CH2- nucleophile, acts towards carbonyl group of oxalacetate
  • -ΔG hydrolysis of CoA intermediate drives forward reaction
57
Q

What occurs during citrate isomerisation? (2nd step citric acid cycle)

A
  • citrate to isocitrate
  • by aconitase
  • removes then adds H2O, shifted from C3 to C4
58
Q

What occurs during 1st decarboxylation? (3rd step citric acid cycle)

A
  • isocitrate to α-ketoglutarate
  • by isocitrate dehydrogenase
  • NADH prod
  • CO2 prod
  • 1st of 4 ox steps
59
Q

What is the importance of CO2 in the citric acid cycle, and why is this the case?

A

Evo of CO2 (decarboxylation) gives strong thermodynamic pull to reaction:
- as CO2 v stable (more so than reactants)
- easily escapes site of reaction (highly soluble in water
and membrane soluble)
- more products than reactants

60
Q

What occurs during 2nd decarboxylation? (4th step citric acid cycle)

A
  • α- ketoglutarate to succinyl CoA (ox of C5 from +3 to +4 and and ox of C4 from +2 to +3)
  • by α- ketoglutarate dehydrogenase
  • prod CO2
  • NADH formed, (-ΔG) coupled to +ΔG succinyl CoA formation
61
Q

What occurs during ATP formation? (5th step citric acid cycle)

A
  • succinyl CoA to succinate
  • by succinyl CoA synthase
  • -ΔG hydrolysis of thioester bond and replacement w/ phosphoester bond (using phosphate from solution)
  • phosphate transferred to ADP (slp)
62
Q

What is the succinyl-CoA synthetase mechanism?

A
  • CoASH 1st displaced by bound phosphate group, forming succinyl phosphate, a ‘high phosphoryl transfer’ compound
  • His side chain then removes Pi group, forming succinate and phosphohistidine
  • then Pi transferred to ADP (slp)
63
Q

What occurs during succinate ox? (6th step citric acid cycle)

A
  • succinate to fumarate
  • by succinate dehydrogenase, a transmembrane protein bound to MIM
  • FAD is co-factor red, as ΔG insufficient to red NAD+
64
Q

What occurs during fumarate hydration? (7th step citric acid cycle)

A
  • fumarate to malate (adding H2O across C=C)

- by fumarase

65
Q

What method did Krebs use to uncover the citric acid cycle?

A
  • Krebs observed adding malate, succinate or fumarate to homogenates of minced pigeon muscle stimulated unusually large O2 uptake (far greater than needed to ox muscles)
  • each acid acting catalytically to stimulate ox of many molecules of some endogenous substance in muscle tissue
66
Q

Why did poison suggest citric acid cycle was a cycle?

A
  • used CA malonate, which closely resembles succinate structure
  • acts as competitive inhibitor of succinate dehydrogenase, which converts succinate to fumarate
  • as malonate poisoned resp in muscle tissues, concluded enzyme must play key role
67
Q

If any of rapidly metabolised acids added (even those downstream) when malonate present, succinate would accum, why?

A
  • pyruvate abundant in muscle, but ox req functioning citric acid cycle
  • if intermediates in low supply, then rate limited
  • therefore adding any of acids greatly stimulates O2 consumption
68
Q

What is the Warburg manometer and how did Krebs utilise it?

A
  • measured pressure change caused by O2 uptake during resp by homogenised tissue sample
  • CO2 absorbed by filter paper soaked on KOH
  • substrate reagents added in side flask and mixed by tipping
69
Q

How is NADH prod by glycolysis imported into mito?

A
  • MIM impermeable to NADH
  • 2 shuttles to transport e-s from cytoplasmic NADH into mito, regen NAD+ for glycolysis
  • glycerol-3-phosphate or malate-aspartate shuttle
70
Q

What occurs during the glycerol-3-phosphate shuttle?

A
  • predominant in muscle, to sustain high OP level by rapidly regen cyto NAD+
  • e-s from cyto NADH red DHAP to G3P
  • ox by glycerol-3-phosphate dehydrogenase
  • co-factor is FAD, red then red UQ to UQH2
71
Q

What occurs during the malate-aspartate shuttle?

A
  • involves 4 enzymes and 2 membrane antiporters
  • 1st cNADH red oxaloacetate to malate
  • malate transported across MIM in exchange for
    α-ketoglutarate
  • malate to oxaloacetate by malate dehydrogenase
  • reforming NADH, now accessible to ETC
  • oxaloacetate membrane impermeable, converted into Asp by transamination
  • NH3 provided by Glu, which is converted into
    α-ketoglutarate
  • Glu and Asp exchanged by other antiporter
  • in cyto, reverse transamination occurs, regen oxaloacetate and Glu
72
Q

How does the amount of ATP prod differ between the 2 shuttles and how is this calculated?

A
  • 4H+/ATP
  • MA shuttle –> for each NADH ox 10H+ transferred across MIM = 2.5 ATPs/NADH
  • G3P shuttle –> or each NADH ox 6 H+ transferred across MIM = 1.5 ATPs
73
Q

What is the advantage of the G3P shuttle?

A
  • irreversible, so operates even when NADH low relative to NAD+
  • MA reversible, so only operates when NADH/NAD+ ratio higher in cytosol than matrix
74
Q

Where are e-s transferred during OP?

A
  • e-s transferred from complex I and complex II to O (terminal e- acceptor) via complexes III and IV
  • e- transfer coupled to H+ transfer across MIM from matrix to IMS
75
Q

What is OP?

A
  • proton transfer reactions leading to formation of H+ grad (pmf) across MIM, harnessed by ATP synthase, to make ATP
76
Q

What is the ETC?

A
  • ‘downhill’ (-ΔG) flow of e-s from -ve to +ve redox pot
  • via series of sequential redox reactions
  • in each reaction donor ox and acceptor red
77
Q

What is redox pot?

A
  • measure of affinity of redox couple for e-s
78
Q

What determines whether something is a reductant or oxidant?

A
  • the more -ve the redox pot, the more likely to donate
    e-s = reductant
  • the more +ve the redox pit, the more likely to donate e-s = oxidant
79
Q

What is chemiosmotic coupling in OP?

A
  • harnessing of free energy from e-s flowing down pot grad to do useful work
  • eg. move H+ from area of low to high conc
80
Q

How are redox pots measured?

A
  • using 2 linked half cells
  • 1 containing equimolar amounts of substance A to be measured in ox and red states
  • other containing 1M solution of H+ (ox) and 1 atmosphere pressure of H2(g)
  • if e-s flow from H half cell to ‘A’ half cell, redox pot more +ve than H, ORA
81
Q

What pH are most biological reactions carried out at?

A
  • pH 7
82
Q

What is the standard redox pot (E0’) and how is it measured?

A
  • measured against H half cell containing 10^-7M solution of H(ox) and 1 atmosphere pressure H2(g)
  • wire provides resistance free route for e- flow
  • voltmeter measures redox pot between cells
  • salt bridge soaked in conc KCL, allowing K+ and Cl- to flow between 2 cells, neutralising any changes as e-s flow between cells
83
Q

What is the equation for calculating ΔGº?

A
  • ΔGº = nFΔE0’
  • where n = no. e-s transferred
  • F = Faraday constant
84
Q

How much NADH, FADH2 and ATP prod per glucose molecule if MA shuttle used? (in glycolysis, link reaction, citric acid cycle and OP)

A
  • NADH = 10
  • FADH2 = 2
  • ATP = 32
85
Q

How much NADH, FADH2 and ATP prod per stearic acid molecule? (in β-ox, citric acid cycle and OP)

A
  • NADH = 36
  • FADH2 = 18
  • ATP = 125
86
Q

What are flavoproteins and how do they feed the (ubiquinone) UQ pool?

A
  • enzymes binding FAD/FADH2 as co-factor
  • eg. complex II
  • provide alt point of entry of e-s into ETS
  • bypass complex I to directly red UQ, so fewer H+ pumped to IMS meaning FADH2 produces less ATP than NADH
87
Q

Why does actual redox pot vary from standard?

A
  • depends on actual conc ratio of ox and red forms
88
Q

What are the 4 complexes in OP?

A
  • I = NADH dehydrogenase
  • II = succinate dehydrogenase
  • III = cytochrome bc1
  • IV = cytochrome c oxidase
89
Q

What is the role of complex I (NADH dehydrogenase)?

A
  • ox NADH to NAD+
  • uses 2e-s to red UQ
  • UQ then binds 2H+ from matrix forming UQH2
  • free energy released used by complex to directly pump 4H+ across MIM
90
Q

What is the overall reaction in complex I (NADH dehydrogenase)?

A
  • NADH + 5H+ (matrix) + UQ –> UQH2 + NAD+ + 4H+ (IMS)
91
Q

What is the structure of complex I (NADH dehydrogenase)?

A
  • matrix arm contains e- transfer cofactors, inc FMN (Flavin mononucleotide) and 9 Fe-S clusters, that link NADH and UQ reaction sites
  • 2e-s passed between co-factors
  • free energy released during e- transfer powers H+ pumping by membrane domain of complex
92
Q

What are the co-factors of complex I (NADH dehydrogenase)?

A
  • NADH ox by FMN co-factor
  • e-s passed through 7 of 9 Fe-S (4Fe4S) clusters and delivered to ox UQ bound at membrane end of matrix arm
  • Fe-S clusters can undergo redox reactions w/o binding and releasing H+, cycling between Fe2+ and Fe3+ ox states
93
Q

How is H+ pumped by complex I (NADH dehydrogenase)?

A
  • mechanism relies on conformational changes induced by free energy released during transport of e-s from NADH (low -ve redox pot) to UQ (high pot) in matrix arm
  • H+ pumped from matrix to IMS
94
Q

What is the role of complex II (succinate dehydrogenase)?

A
  • ox succinate to fumarate as part of citric acid cycle
  • uses 2e-s to red UQ
  • then UQ binds 2H+ from matrix forming UQH2
  • no H+ directly pumped
95
Q

What is the overall reaction in complex II (succinate dehydrogenase)?

A
  • succinate + UQ –> fumarate + UQH2
96
Q

What is the structure of complex II (succinate dehydrogenase)?

A
  • e-s from succinate reaction site in matrix arm of complex 1st passed to bound FAD
  • then via 3 Fe-S clusters
  • and finally via bound haem molecule to UQ reaction site
97
Q

What is ubiquinone?

A
  • coenzyme Q10
  • lipid soluble e- carrier that takes e-s from complex I and II to III
  • takes up H+ from matrix when red and releases them to IMS when ox (= proton translocation)
98
Q

What is the role of complex III (cytochrome bc1)?

A
  • ox UQH2 to UQH and transfers e-s to cytochrome c
  • H+ from UQH2 released into IMS
  • 2 additional H+ translocated from matrix to IMS for every UQH2 ox (Q cycle)
99
Q

What is the overall reaction in complex III (cytochrome bc1)?

A
  • UQH2 + 2Cyt c (ox) + 2H+ (matrix) –> UQ + 2Cyt c (red) + 4H+ (IMS)
100
Q

What occurs during the Q cycle?

A
  • 2e-s from ox of UQH2 passed along 2 separate co-factor chains
  • 1st via Fe-S cluster and haem to red cyt c
  • 2nd via 2 haems to red another UQ
  • once 2nd UQH2 ox at site 1, UQH2 can be gen at site 2
101
Q

What is the purpose of the Q cycle?

A
  • doubles no. H+ translocated per UQH2 ox
102
Q

What is cytochrome c?

A
  • small (approx 10kD) soluble protein e- carrier

- each cyt c binds 1 e-, red Fe3+ to Fe2+in bound haem co-factor

103
Q

What is the role of complex IV (cytochrome c oxidase)?

A
  • transfers e- from cyt c to O2
  • 2e-s from 2 cyt c and 2H+ from matrix req to red 1/2O2 to H2O
  • free energy released in reaction used to directly pump 2H+ from matrix to IMS
104
Q

What is the structure of complex IV (cytochrome c oxidase)?

A
  • 2e-s from 2 cyt c molecules passed via pair of bound Cu2+ co-factors to haem and finally to haem/Cu pair
  • Cu2+ cycle between Cu+ and Cu2+ ox states
  • e-s used to red O2 to water
105
Q

What is the overall reaction in complex IV (cytochrome c oxidase)?

A
  • 2Cyt c (red) + 4H+ (matrix) + 1/2 O2 –> 2Cyt c (ox) + H2O + 2H+ (IMS)
106
Q

What was MItchell’s hypothesis?

A
  • ec grad gen by e- transport used to gen ATP
107
Q

What is the evidence for chemiosmosis?

A
  • when actively respiring, ratio of matrix to IMS vol changes dramatically, suggesting e- transport coupled to change in osmotic pot
  • if H+ grad formed by e- transport needed to gen ATP, then its abolition should inhibit ATP formation, H+ grad can be abolished by uncoupler (eg. 2,4-DNP), molecule which facilitates diffusion of H+ across normally impermeable membrane
  • light driven H+ pump ‘bacteriorhodopsin’ could when reconstituted in lipid vesicles w/ ATP synthase drive ATP prod, proving no ‘high energy intermediates’ req
108
Q

What occurs during 1 full turn of F0 rotor ring?

A
  • 8H+ carried across membrane

- causing 1 full turn of F1 ATPase head, forming 3 molecules ATP

109
Q

What is the overall reaction occurring in ATP synthase?

A
  • 8H+ (IMS) + 3ADP +3Pi –> 3ATP + 8H+ (matrix)
110
Q

What is the structure of the 2 domains of ATP synthase?

A
  • F1 domain protrudes out of MIM into matrix and comprised of 9 major subunits α3β3γε
  • F0 domain embedded in MIM, comprised of 8-15 subunits, 1 a subunit and b2 subunit which acts as stator
111
Q

How does the ATP synthase H+ pumping mechanism work?

A
  • C subunits have Asp residue at MIM centre
  • accepts H+ which enter via subunit half-channel
  • when exposed to H+ rich IMS, Asp takes up H+
  • when eventually (after full rotation of c-ring) it’s exposed to H+ poor matrix, releases H+
112
Q

What is the mechanism for the ATP synthase H+ pump? (ATP synthase domains)

A
  • rotation of c-subunit causes γ-subunit at centre to rotate
  • couples H+ movement down conc grad to rotation of F1 domain
  • pmf drives c-ring rotation
  • 3 β-subunits of F1 domain can exist in 3 conformations, which bind ATP tightly (T), loosely (L) or release it (open, O)
113
Q

What occurs during the binding change model? (ATP synthase H+ pumping mechanism)

A
  • rotation of γ-subunit interconverts conformation of 3 β-subunits between 3 states
  • in O state, ATP released
  • in L state, ADP + Pi bound
  • in T state, ADP + Pi –> ATP
  • req 8H+ to complete full rotation and forms 3 ATP (so 2.7H+/ATP)
114
Q

What 2 components is the pmf formed of?

A
  • membrane pot (ΔΨ)

- H+ conc grad

115
Q

What is membrane pot?

A
  • difference in charge between 2 sides of membrane
116
Q

What general kind of units does pmf have?

A
  • voltage
117
Q

How is ATP exported from mito?

A
  • highly charged ATP and ADP molecules don’t readily cross biological membranes
  • instead transported via ATP-ADP translocase
  • charge on ATP = -4, and ADP = -3
  • so net exchange of ATP (out) for ADP (in) results innet movement of 1 -ve charge from matrix to cytosol
  • driven by transmembrane ΔΨ formed via e- transport
118
Q

When does substrate level phosphorylation occur in glycolysis?

A
  • 1,3BPG to 3-phosphoglycerate (7 - 1st phosphate transfer to ADP)
  • phosphoenolpyruvate to pyruvate (10 - 2nd phosphate transfer to ADP)
119
Q

When does substrate level phosphorylation occur in the citric acid cycle?

A
  • succinyl CoA to succinate (5 - ATP formation)
120
Q

What occurs during malate ox? (8th step citric acid cycle)

A
  • malate to oxalacetate (OH to C=O)
  • by malate dehydrogenase
  • NADH prod

MBB161 (6 decks)

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