Johnson (Cellular Respiration) Flashcards
What is the difference between anabolism and catabolism?
- anabolism = making stuff, mainly endergonic (+ΔG)
- catabolism = breaking stuff down, mainly exergonic
(-ΔG)
What is the relationship between catabolism and anabolism?
- catabolism provides energy for anabolism
What is cellular respiration?
- catabolic breakdown of red C derived from fats and sugars to gain energy
What is glycolysis?
- central ATP prod pathway
- in cytosol
- involves 10 enzymatic reactions
Where do heterotrophs obtain energy from?
- ox red C sources, eg. sugars and fats
Why are reactions in respiration carried out stepwise?
- to release energy in controlled way, so it can be captured and stored in activated carrier molecules
How does ox of C compounds provides energy?
- 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
Which part of respiration is common to animals, plants and many bacteria?
- glycolysis
To what extent is O involved in glycolysis?
- not req
- but involved as e-s removed from C to NADH
What is the net gain from glycolysis?
- 2 ATP
- 2 NADH
- 2 pyruvate
What are the 10 steps of glycolysis?
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
What occurs during glucose phosphorylation, and what is the role of the negative charge on the Pi? (1st step glycolysis)
- 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
Why is ATP less stable than ADP + Pi?
- negative phosphate charges repel
- lower entropy
- less interactions w/ water
- free Pi stabilised by resonance structures, not poss when bound to ATP
In terms of equilibrium, which is favoured, ATP or ADP + Pi?
- ADP + Pi greatly favoured
What happens to reaction in terms of ATP prod, depending on ΔG value?
- 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
Why is there no such thing as a high energy bond, what is really meant?
- 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
What is req for 2 reactions to be coupled?
- must share 1 or more intermediates
What is the ΔG of coupled reactions?
- sum of 2 individual reactions
What occurs during isomerisation to fructose, what kind of sugars are converted and is it reversible? (2nd step glycolysis)
- G6P to F6P
- by phosphoglucose isomerase
- aldose sugar converted to ketose sugar (necessary for step 4)
- readily reversible under cellular conditions
What occurs during 2nd phosphorylation, and how is entry of sugars into glycolysis controlled at this step? (3rd step glycolysis)
- 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
What occurs during cleavage? (4th step glycolysis)
- 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
What occurs during conversion of DHAP? (5th step glycolysis)
- DHAP –> GADP
- K greatly in favour of DHAP, but reaction proceeds as GADP constantly removed by glycolysis pathway
What occurs during oxidation of GADP? (6th step glycolysis)
- GADP to 1,3-bisphosphoglycerate (compound w/ high phosphoryl transfer pot)
- by glyceraldehyde-3-phosphate dehydrogenase
- NADH formed
- 1st energy gen step
What are the common activated carrier molecules?
- NADH
- FAD/FADH2
- CoASH
Why is ox coupled to phosphorylation by enzyme linked intermediate during oxidation of GADP? (6th step glycolysis)
- 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
What occurs during 1st phosphate transfer to ADP? (7th step glycolysis)
- 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
What is substrate level phosphorylation?
- transfer of Pi from compound w/ high phosphoryl transfer pot to ADP
What is oxidative phosphorylation
- transfer of Pi from compound w/ low phosphoryl transfer pot to ADP
What occurs during isomerisation to 2-phosphoglycerate? (8th step glycolysis)
- 3-phosphoglycerate to 2-phosphoglycerate
- by phosphoglycerate mutase
- remaining phosphodiester linkage, w/ relatively low phosphoryl transfer pot, transferred from C3 to C2
What occurs during removal of water? (9th step glycolysis)
- 2-phosphoglycerate to phosphoenolpyruvate
- by enolase
How is high-phosphoryl transfer pot compound made from low pot compound, where did energy come from? (9th step glycolysis - removal of water)
- 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
What occurs during 2nd phosphate transfer to ADP? (10th step glycolysis)
- phosphoenolpyruvate to pyruvate
- by pyruvate kinase
- transfer of phosphate group to ATP
- 3rd energy gen step
- substrate level phosphorylation
What happens to ATP and NADH at end of glycolysis?
- ATP used directly in cyto to power cellular processes
- NADH imported into mito for OP to gen more ATP
What is the Warburg effect?
- tumours have enhanced glycolysis and glucose uptake
- metabolise glucose through to lactate even when O2 present
Why is the Warburg effect an advantage to cancer?
- 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
How can Warburg effect be used to monitor cancer cells?
- 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
What is fermentation?
- making ATP w/o O2
What happens in absence of O2 at end of glycolysis?
- no further ox of pyruvate
- won’t proceed due to redox imbalance
How does NAD+ regen to restore redox imbalance and allow glycolysis to continue w/o O2
- 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
What occurs during fermentation in muscle tissue?
- pyruvate converted to lactate
What occurs during fermentation in yeast and bacteria?
- pyruvate converted to acetaldehyde (2H+ –> 2CO2)
- acetaldehyde converted to ethanol and NAD+ regen in this step
What happens to pyruvate under aerobic conditions?
- pyruvate ox to acetyl CoA and CO2 by pyruvate dehydrogenase complex in mito matrix
- contains 3 diff enzymes and 60 polypeptide chains
What is the role of CoASH?
- 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
What are 3 steps of the Link Reaction?
1) decarboxylation of pyruvate
2) oxidation of hydroxyethyl group
3) red of NAD+
What occurs during decarboxylation of pyruvate? (1st step link reaction)
- CO2 removed from pyruvate
- by pyruvate decarboxylase (PD)
- resulting hydroxyethyl group binds to thiamine pyrophosphate (TPP), a co-factor of PD
What occurs during oxidation of hydroxyethyl group? (2nd step link reaction)
- 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
What occurs during red of NAD+? (3rd step link reaction)
- red lipoamide ox by dihydrolipoyl dehydrogenase
- FADH2 formed, used to red NAD+ to NADH
What does NADH stand for?
- nicotinamide adenine dinucleotide
What does FAD stand for?
- flavin adenine di-nucleotide
What is FAD capable of?
- carrying 2e-s, but binds 2H+ when red
What is the role of pyruvate dehydrogenase complex (PDH) in the link reaction?
- PDH organisation min distance highly reactive substrates have to travel between active sites
- this substrate channeling increases reaction rate and decreases unwanted side reactions
How are FAs used as a source of acetyl CoA?
- 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
What occurs during β ox of FAs?
- 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)
Why is the Krebs cycle necessary? (biochemical logic)
- 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
What are the 8 steps in the citric acid cycle?
1) citrate formation
2) citrate isomerisation
3) 1st decarboxylation
4) 2nd decarboxylation
5) ATP formation
6) succinate ox
7) fumarate hydration
8) malate ox
What occurs during citrate formation? (1st step citric acid cycle)
- 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
What occurs during citrate isomerisation? (2nd step citric acid cycle)
- citrate to isocitrate
- by aconitase
- removes then adds H2O, shifted from C3 to C4
What occurs during 1st decarboxylation? (3rd step citric acid cycle)
- isocitrate to α-ketoglutarate
- by isocitrate dehydrogenase
- NADH prod
- CO2 prod
- 1st of 4 ox steps
What is the importance of CO2 in the citric acid cycle, and why is this the case?
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
What occurs during 2nd decarboxylation? (4th step citric acid cycle)
- 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
What occurs during ATP formation? (5th step citric acid cycle)
- 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)
What is the succinyl-CoA synthetase mechanism?
- 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)
What occurs during succinate ox? (6th step citric acid cycle)
- succinate to fumarate
- by succinate dehydrogenase, a transmembrane protein bound to MIM
- FAD is co-factor red, as ΔG insufficient to red NAD+
What occurs during fumarate hydration? (7th step citric acid cycle)
- fumarate to malate (adding H2O across C=C)
- by fumarase
What method did Krebs use to uncover the citric acid cycle?
- 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
Why did poison suggest citric acid cycle was a cycle?
- 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
If any of rapidly metabolised acids added (even those downstream) when malonate present, succinate would accum, why?
- 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
What is the Warburg manometer and how did Krebs utilise it?
- 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
How is NADH prod by glycolysis imported into mito?
- 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
What occurs during the glycerol-3-phosphate shuttle?
- 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
What occurs during the malate-aspartate shuttle?
- 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
How does the amount of ATP prod differ between the 2 shuttles and how is this calculated?
- 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
What is the advantage of the G3P shuttle?
- irreversible, so operates even when NADH low relative to NAD+
- MA reversible, so only operates when NADH/NAD+ ratio higher in cytosol than matrix
Where are e-s transferred during OP?
- 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
What is OP?
- proton transfer reactions leading to formation of H+ grad (pmf) across MIM, harnessed by ATP synthase, to make ATP
What is the ETC?
- ‘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
What is redox pot?
- measure of affinity of redox couple for e-s
What determines whether something is a reductant or oxidant?
- 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
What is chemiosmotic coupling in OP?
- 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
How are redox pots measured?
- 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
What pH are most biological reactions carried out at?
- pH 7
What is the standard redox pot (E0’) and how is it measured?
- 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
What is the equation for calculating ΔGº?
- ΔGº = nFΔE0’
- where n = no. e-s transferred
- F = Faraday constant
How much NADH, FADH2 and ATP prod per glucose molecule if MA shuttle used? (in glycolysis, link reaction, citric acid cycle and OP)
- NADH = 10
- FADH2 = 2
- ATP = 32
How much NADH, FADH2 and ATP prod per stearic acid molecule? (in β-ox, citric acid cycle and OP)
- NADH = 36
- FADH2 = 18
- ATP = 125
What are flavoproteins and how do they feed the (ubiquinone) UQ pool?
- 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
Why does actual redox pot vary from standard?
- depends on actual conc ratio of ox and red forms
What are the 4 complexes in OP?
- I = NADH dehydrogenase
- II = succinate dehydrogenase
- III = cytochrome bc1
- IV = cytochrome c oxidase
What is the role of complex I (NADH dehydrogenase)?
- 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
What is the overall reaction in complex I (NADH dehydrogenase)?
- NADH + 5H+ (matrix) + UQ –> UQH2 + NAD+ + 4H+ (IMS)
What is the structure of complex I (NADH dehydrogenase)?
- 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
What are the co-factors of complex I (NADH dehydrogenase)?
- 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
How is H+ pumped by complex I (NADH dehydrogenase)?
- 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
What is the role of complex II (succinate dehydrogenase)?
- 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
What is the overall reaction in complex II (succinate dehydrogenase)?
- succinate + UQ –> fumarate + UQH2
What is the structure of complex II (succinate dehydrogenase)?
- 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
What is ubiquinone?
- 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)
What is the role of complex III (cytochrome bc1)?
- 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)
What is the overall reaction in complex III (cytochrome bc1)?
- UQH2 + 2Cyt c (ox) + 2H+ (matrix) –> UQ + 2Cyt c (red) + 4H+ (IMS)
What occurs during the Q cycle?
- 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
What is the purpose of the Q cycle?
- doubles no. H+ translocated per UQH2 ox
What is cytochrome c?
- small (approx 10kD) soluble protein e- carrier
- each cyt c binds 1 e-, red Fe3+ to Fe2+in bound haem co-factor
What is the role of complex IV (cytochrome c oxidase)?
- 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
What is the structure of complex IV (cytochrome c oxidase)?
- 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
What is the overall reaction in complex IV (cytochrome c oxidase)?
- 2Cyt c (red) + 4H+ (matrix) + 1/2 O2 –> 2Cyt c (ox) + H2O + 2H+ (IMS)
What was MItchell’s hypothesis?
- ec grad gen by e- transport used to gen ATP
What is the evidence for chemiosmosis?
- 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
What occurs during 1 full turn of F0 rotor ring?
- 8H+ carried across membrane
- causing 1 full turn of F1 ATPase head, forming 3 molecules ATP
What is the overall reaction occurring in ATP synthase?
- 8H+ (IMS) + 3ADP +3Pi –> 3ATP + 8H+ (matrix)
What is the structure of the 2 domains of ATP synthase?
- 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
How does the ATP synthase H+ pumping mechanism work?
- 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+
What is the mechanism for the ATP synthase H+ pump? (ATP synthase domains)
- 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)
What occurs during the binding change model? (ATP synthase H+ pumping mechanism)
- 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)
What 2 components is the pmf formed of?
- membrane pot (ΔΨ)
- H+ conc grad
What is membrane pot?
- difference in charge between 2 sides of membrane
What general kind of units does pmf have?
- voltage
How is ATP exported from mito?
- 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
When does substrate level phosphorylation occur in glycolysis?
- 1,3BPG to 3-phosphoglycerate (7 - 1st phosphate transfer to ADP)
- phosphoenolpyruvate to pyruvate (10 - 2nd phosphate transfer to ADP)
When does substrate level phosphorylation occur in the citric acid cycle?
- succinyl CoA to succinate (5 - ATP formation)
What occurs during malate ox? (8th step citric acid cycle)
- malate to oxalacetate (OH to C=O)
- by malate dehydrogenase
- NADH prod
