6a Flashcards
where does the krebs cycle // citric acid cycle occur and what does it do
it occurs in the mitochondria
its the aerobic oxidation of pyruvate
or the oxidation of all fuels such as lipids, amino acids and sugars.
Krebs cycle: oxidation of fuels!! what form do fuels enter the krebs cycle in
they enter the cycle as acetyl coenzyme A
end product of glycolysis is
pyruvate
what comes after glycolysis
krebs cycle
whats the starting material of the krebs cycle
the starting material is acetyl coenzyme A
where does glycolysis occur in
the cyctoplasm
does glycolysis produce a lot of ATP
nope!!
u only get 2ATP and 2 pyruvate from 1 glucose molecule.
for glycolysis to occur,, what needs to keeo happening
NAD+ needs to keep being regenerated or else the cycle stops!!
what processes regenerate NAD+
fermentation and the lactic acid cycle regenerate NAD+
what part of acetyl coenzyme A do we need to remember,, the lhs but describe it
Me carbonyl S, C C NH carbonyl
thats the structure we care about.
whats an acetyl group
an acetyl group is the carbonyl group with an Me as one of the R groups.
looks like acetone kinda ig
okay so if acetyl coenzyme A has 2 important acetyl groups in the part we are about,, and its the starting material of the krebs cycle,, what does the krebs cycle do to the 2 acetyl groups
it oxidises the 2 acetyl groups into CO2!!
from glucose,, glycolysis to the krebs cycle, what happens to all of the carbons
the. arbons are converted into CO2 in a series of step wise reactions,, these reactions give out energy in small amounts.
describe the cycle of the krebs // citric aiid cycle
start // top = acetyl coenzyme A
- 2CO2 (oxidation of the 2 acetyl groups)
- 8e- (from the NADH and FADH)
- 1GTP
back the the beginning
what happens after the krebs cycle // cirtric acid cycle
oxidative phosphorylation!!
what links the krebs sycle and oxidative phosphorylation + what happens in it
the 8e- we get from NADH and FADH (the e- come from the H)
they’re given out during the krebs cycle and enter oxidative phosphorylation.
where they enter the electron transport chain and reduce 2O2 to give 4H20
okay so the 8e- enter oxudative phosphorylation and reduce 2O2 to give 4H20,, what else happens in oxidative phosphorylation and what powers this
ADP + Pi —> ATP.
atp synthesis is here!!! this is the reaction where most our ATP is regenerated from.
this ATP synthesis is powered due to the H+ gradient,, aka proton gradient which gets pumped in.
what regenerates NAD+ from NADH
fermentation, lactic acid fermentation
and the reduction of 2O2 into 4H20!! bc the e- we use to reduce come from the H’s in NADH and FADH!!! so yhhh
how do we convert pyruvate to acetyl coenzyme A
- decarboxylation
- oxidation
- pyruvate + coenzyme A(long chain thiol) + NAD+
— pyruvate dehydrogenase—> acetyl coenzyme A + CO2 + NADH + H+
going from pyruvate to acetyl coenzyme A,, what enzyme do we use
we use pyruvate dehydrogenase
pyruvate dehydrogenase exp
3 distinct enzymes:
- pyruvate dehydrogenase: TPP: oxidative carboxylation (-CO2 from pyruvate by attaching it to the NS nucleophilic heterocycle)
- dihydrolipoyl transcetylase: lipoamide: acetyl transfer
- dihydrolipoyl dehydrogenase: FAD: regenerates lipoamide!!!
describe the mechanism of pyruvate decarboxylation
the NS heterocycle has an acidic H between the N and S.
this is removed and forms a (-),, this attack the keto bit of pyruvate as its more electrophilic than the ester bit.
decarboxylation then occurs as the OH e- go to the C-O bond to form CO2. which then kicks itself off the molecule,, gives the bigger molecule a C=C enol double bond,, and then neutralises (+) nitrogen
enol carbons are normally what
theyre normally nucleophilic as the O,, or any other heteratoms can use their lone pairs to resonate their lone pairs towards it,, allowing the C=C to attack an electrophile.
describe pyruvate dehydrogenase and lipoamide (E2)
we have the lipoamide which is the S-S heteroamide
the S-S is electrophilic and can therefore be attacked by a nucleophile such as the NCS heterocycle with the anion on the C.
when this ttacks the S-S it opens the ring
deprotonation then occurs to kick the NCS ring off the lipoamide to form an acetyl protected thiol. bc theres 2 acetyles on both ends and thiols in between.
