citric acid cycle Flashcards
stage one of citric acid cycle is
acetyl coA production
pyruvate undergoes ____ ___ to produce acetyl co a
oxidative decarboxylation
the citric acid cycle occurs in
mitochondrial matrix
within step one of aerobic respiration (citric acid cycle) there are ___ seperate enzymatic activities and _ cofactors
3, 5
what are the five cofactors
TPP, NAD, lipoate, FAD, Coa-SH
catabolic
breaking down
NAD is an electron carrier and carries __ electrons
2
TPP does what two actions
C-C bond cleavage and two carbon transfer
there are three major steps of respiration what are they
- acteyl co a production
- acetyl co a oxidation
- electron transfer and oxidative phosphorylation
respiration is all about pushing ___
electrons
with acetyl coa procution by pyruvate there is what relwased
co2
the enzyme complex used to convert pyruvate to acetyl coa is
pyruvate dehydrogenase complex (has three subunits)
pyruvate dehydrogenase complex has ____ ____ in which intermediated never leave the complex
substrate channeling
lipoate is convently bound to a ____ on E2; the result is
lysine; lipoamide
FAD is an ___ ____
electron acceptor
E2 has two domains, lysine to which the lipoate is attached is in one but the the other is an ____
active site
lipoate can exist in three states
- oxidized
- reduced
- acetylated
lipoate can carry ___ and ____
electrons and acetyl co a
FAD cannot ____ it is present and attached to E3 subunit
leave (NAD can move in and out )
coezyme A carries ____ groups; has a reactive thiol group
acetyl
TPP has an _____ _____ which readily leaves
acidic proton
once the proton leaves the E1 TPP will readily attack the incoming carbonyl carbon of ___; which releases CO2
pyruvate
the remaing part of the pyruvate on TPP gets converted to _____
hydroxyethyl TPP
The E2 lipoamide has a lysine amino acid linker which will swing into E1 and coverted that group in E1 to what
acytelated lipoamide
next in E2 subunit CoA will diffuse in and pick up acetyl group to become
acetyl CoA
the reduced lipoamide drops off electrons to FAD (E3) making it
FADH2
NAD will pick up electrons from FADH2 and becomes
NADH2
Once pyruvate is converted to Acetyl CoA it is irreversible but Acetyl CoA can either go to ___ __ __ or _ _ _
citric acid cycle or fatty acid synthesis
high levels of ATP would cause Acetyl CoA to choose
fatty acid synthesis
The PDH complex is alosterically regulated by __ ____ and ___
AMP, CoA and NAD+
The PDH complex is ___ by dephosphorylation of E1
activated
stage 2 of the citric acid cycle uses 2C (acetyl coa) which enters and combines with ____
4C oxaloacetate
used in both anabolic and catabolic processes; intemediates leave/join at different points
amphibolic (citric acid cycle does this)
the 6C molecule formed from acetyl coA and oxaloacetate is
citrate
step one is a condensations step where acetyl coA and oxaloacetate are are combined. What enzyme is used? which gives you?
citrate synthase; citrate
step 2 is generating a better substrate for step 3; which ___ to ____
citrate to isocitrate
citrate is a ____ alcohol which makes it a poor substrate for oxidation
tertiary
the intermediate between citrate and isocitrate is
cis-aconitate
____ is the enzyme which helps use water to change citrate to isocitrate
aconitase
_____ of the citrate leads to cis C double bond C
dehydration
step 3 is the first oxidation in which isocitrate becomes oxidized by ____
NAD
step 3 is catalyzed by ____ ____ and requires manganese ion to stabilize
isocitrate dehydrogenase
isocitrate is converted to ____ by NAD (oxidation) then to ____ with release of (decoarboxylation)
oxalosuccinate; alpha ketoglutarate
step 4 is the second oxidation where alpha ketoglutarate gets converted to ____ ____ (oxidative decarboxylation)
succinyl-CoA
step 3 ends in succinyl-CoA which results in high group transfer potential with ___
thioester
step 5 is a substrate level phosphorylation where succinyl coA becomes _____
succinate
step 5 generates ____
GTP
catalyzes condensation reactions using energy of NTPs
synthetase
what enzyme converts succinyl coA into succinate (enzyme is not named correctly; typically there will be a breakage or cleavage yet that does not happen)
succinyl-CoA synthetase
step 5 also produces a ____
GTP
all triphosphates are essentially ____ and interconvertible in terms of energy
equal
step 6 is the third oxidation in which succinate is converted to ____
fumarate
what enzyme is used for step 6
succinate dehydrogenase
step 6 is the only reaction in which ____ is the electron acceptor
FAD
succinate dehydrogenase is the only enzyme not in the ___; it is bound to inner mitochondrial matrix
matrix
step 7 is hydration where fumarate becomes ____ (uses fumarase as enzyme)
malate
within step 7 addition of water occurs in two steps what are they
- hydroxylation generates a carbanion
- protonation neutralizes the carbanion
fumarase only adds water in ___ across the double bond
trans
step 8 is an oxidation where you go from L-malate to (high G- unfavorable; product removal pushes it forward!)
oxaloacetate
in step 8 ___ is the electron acceptor and the enzyme is
NAD, and malate dehydrogenase
one ___ is produced per cycle
GTP
electrons from cirtic acid cycle REDUCE NAD+ and FAD; which are then used to make ATP there are ___ ATP per FADH2 and ___ ATP per NADH
1.5, 2.5
every 4 protons gives you one ATP and NADH pushed ten protons so ___ ATP per NADH
2.5
alpha ketoglutarate can leave pathway and make ___
purines
pyruvate can make oxaloacetate to make aspartate which makes
amino acids, purines and pyrimidines
the ____ reaction is when pyruvate will bind to bicarboinate in presence of ATP and ezyme is ___ will give you oxaloacetate to run citric acid cycle (you have to have it!!)
analplerotic; pyruvate carboxylase
the anaplerotic reaction will replenish ___ for the cycle
metabolites
pyruvate carboxylase wont function unless acetyl coA is abundant, why?
acetyl coA will build up and will activate oxaloacetate which can then make citrate
high acetyl coA negatively regulated PDH; why?
high acetyl CoA shows a fed state so don’t need to run citric acid cycle
