7a Flashcards
when we release CO2 in a reaction,, where did it come from + how can we be sure
the CO2 we release does not come from from the carbons in ACETYL COENZYME A.
it comes from the oxaloacetate!!!
we know this from labelling studies
why is it hard to differentiate what CO2 in lost when looking at citrate
bc citrate is achiral,, meaning its not bonded to 4 diff things,, meaning that 2 of the things are the same.
so its hard to figure out what C is released
what is prochirality
when replacement of a stereoheterotopic ligand in an achiral environment gives rise to a chiral product.
AKA when we add a different ligand to an achiral molecule,, we get a chiral one.
when smt has R configuration,, what pro is it
its pro - r
when smt has S configuration,, what pro is it
its pro s
when we add a different ligand to an achiral molecule, ,to get a chiral one,, what do we assume about the added ligand
we assume it has a larger priority than the one we’re replacing it with.
aka if u have 2 H’s we replace one of them with D,, as it has a higher priority as its heavier.
when smt is pro-r what does it mean
it meas that if we were to replace it with a higher priority group,, we would get r configuration.
apart from D,, what else can we use to make an achiral molecule chiral
we can use diff isotopes of a molecule.
aka instead of 12C we can change one of the idential goups to 13C.
whats special about enantiomers in chiral and achiral environments
in achiral environments the enantiomers react at the same rate
in chiral environments the enantiomers react at different rates
what does a chiral environment allow us to do
it allows us to distinguish differences between pro-r and pro-s.
if we have an achiral substrate and an enzyme.
aka the 2 things that are identical (a + a’) will not be able to both align with the (a) binding site
what enzyme can distinguish between pro-s and pro- r side chains and what does this mean
the aconitase nzyme can distinguish between pro - r and pro-s
meaning that it wont remove the C from acetyl coenzyme A during decarboxylation.
they wont be removed from citrate
the side we form the enolate on is what
its the side that is decarboxylated when citrate is reacted with aconitase
aconitase and citrate,, what happens
first the middle CO2 is removed..
then the pro - r or pro-s CO2 is removed!!!!
HERE WE NORMALLY ENOLISE THE PRO-R SIDE THO!! MEANING THAT THE PROR SIDE IS THE ONE THAT HAS ITS CO2 REMOVED
if the pro-r CO2 is removed from citrate by aconitase,, what side does acetyl coenzyme have to attack the oxaloacetate in
the si face!!
so that those carbons are pro-s
so theyre not pro-r
so theyre not removed by aconitase.
how is acetylcoenzyme added to oxaloacetate
its turned into an enolate which then attacks the ketone of oxaloacetate.
then the ketone becomes an OH when we protonate.
why do we attack the ketone and not the carboxylate
bc theres no lone pair making the C less electrophilic in the ketone portion.
okay so when adding acetyl coenzyme A to oxaloacetate what must we do
enzymes must be specific ,, aka citrate synthase,, and add acetyl coenzyme A to the SI FACE in order to not lose those carbons when decarboxylation occurs.
okay so bc the 2C’s from acetyl coenzyme A were added on the si phase and are pro-s,, what means that the carbons on succinate areeeee
the 2 carbons on the lhs of succinate are the 2 carbons we got from acetylcoenzyme A bonding to the oxaloacetate.
what happens to succinate to get to oxaloacetate
a series of oxidation reactions
what is used for oxidation reactions
we normally use NAD or FAD to get NADH or FADH2!!!
the high energy e- we get from the CH bonds are used to power oxidative phosphorylation
what oxident is used to go from an alkane to an alkene
FAD
turns into FADH2
what reducing agent is used to go from alkene to alkane
FADH2
forms FAD.
succinate gets turned itnoooo
fumarate!!!
using succinate dehydrogenase
FAD turns into FADH2
the e- from FADH2 pass into the ETC
what happens going from a succinate to a fumarate: oxidation or reduction
oxidation!!!
from an alkane to an alkene
this alkene is not nucleophilic but electrophilic due to it being in conjuagtion to EWG.
aka smt can attck it and the alkene e- can be conjugated onto the EWG.
