Lecture 16 - link reaction and citric acid cycle Flashcards
what could happen after pyruvate
aerobic = gets oxd to acetyl coA (link reaction)
anarobic = converted to ethanol
or lactate
depedning on cell type
what enzyme converts pyruvate into acetyl coa
pyruvate dehydrogenase
(which converts NAD+ to NADH and also decarboxylates pyruvate)
what bond is high energy bond in Acetyl coA
thioester bond between acetyl group and coA
-31kJ mol
composition of pyruvate dehydrogenase complex
24x E1
24x E2
12x E3
60 total proteins make up the enzymje
function of E1
pyruvate oxidative decarboxylation
so removes acetyl group
function of E2
transferring acetyl group to coA
function of E3
cofactor regeneration
why does pyruvate need to pass into the mitochondria
pyruvate dehydrogenase is in the mt
how does pyruvate pass into mt
can cross outer memb easy
inner memb needs to pass through pyruvate translocase (a pyruvate/H+ symporter)
“first” step of citric acid cycle
oxaloacetate (4C) added to acetyl coA (2C)
to make citrate (6C)
and CoA comes off in a condensation reaction
what stage is the first NADH and CO2 formed and how
isocitrate turns to alpha-ketoglutamate
via isocitrate dehydrogenase
what stage is the first NADH and CO2 formed and how
isocitrate turns to alpha-ketoglutamate
via isocitrate dehydrogenase
when is 2nd NADH and CO2 formed
alpha ketoglutarate turns to succinyl-coA
via the corresponding dehydrogenase
(remember, coA added at this stage)
at what stage does substrate level phosph occur
succinyl-CoA turns to succinate
via succinyl-coa synthetase
and GDP/ADP turns to GTP/ATP
and coA comes off
what stage is FADH2 made
succinate to fumarate
via succinate dehydrogenase
when is the final NADH formed
after fumarate hydrated to malate
malate turns back into oxaloacetate via malate dehydrogenase
total NADH, FADH2, GTP/ATP and CO2 formed after citric acid cycle (per cycle not per glucose)
3 NADH
2 CO2
1 FADH2
1 ATP/GTP
how many ATP formed from each NADH and FADH2
n = 2.5
f = 1.5
total amount of ATP made from whole process from 1 glucose
30-32
why is it 3 or 5 ATP made
the nadh from glycolysis has to pass thorugh either the
- malate-aspartate shuttle (makes 2.5)
or
- glycerol phosphate shuttle (in brown adipose tissue, makes 1.5)
what allows NADH to be oxd in malate aspartate shuttle
oxaloacetate
oxides NADH and in turn gets turned into malate
malate passes through into the mito matrix and reduces another NAD+ into NADH
so overall 1 NADH passes into matrik
what 2 things cause feedback inhibition of pyruvate dehydrogenase
acetyl coA inhibits E2
NADH inhibits E3
what will allow feed forward activation of pyruvate dehydrogenase
lots of NAD+
what would cause the rate of the citric acid cycle decrease
lots of ATP
