TCA cycle Flashcards
which stage of glucose oxidation occurs in the cytoplasm of the cell?
glycolysis
how many co2 are produced in ten turns of tca?
2x10=20
which stage of respiration produces the most ATP directly when glucose is completely oxidized to carbon dioxide and water?
ETC and chemiosmosis
The oxygen consumed during cellular respiration is directly involved in…
accepting e in ETC
When hydrogen ions (H+) are pumped across the inner mitochondrial membrane, they form a proton gradient. ATP is then formed by a process called…
oxidative phosphorylation
In aerobic respiration, the electrons associated with the hydrogen atoms in glucose are transferred to…
oxygen through many steps
NADH + H+ is oxidized during which stage(s) of aerobic respiration in the cell?
ETC
making the entire inner mitochondrial membrane permeable to H+ would stop ?
atp synthesis
Where is the electron transport chain for cellular respiration located in a plant cell?
inner membrane of mitochondria
all of the following are produced in glycolysis except...
ATP
pyruvate
carbon dioxide
NADH + H+
heatco2
TCA cycle occurs in…
mitochondrial matrix
in prokaryotes, tca occurs in
cytosol (proton gradient across PM)
how many enzymes does cycle use?
names?
8
- citrate synthase
- aconitase
- isocitrate dehydrogenase
- alpha ketoglutarate dehydrogenase
- succinyl coA synthetase
- succinate dehudrogenase
- fumarase
- malate dehydrogenase
from beginning to end, what is oxidized to what?
acetyl coa –>2 co2
Net products of tca
two turns (2 acetylcoA) give: 2GTP 6NADH 2FADH2 2CO2 (one turn of cycle is half of that)
primary source of acetyl coa for tca?
glycolysis , sugar breakdown
what converts pyruvate from glycolysis to acetyl coa?
pyruvate dehydrogenase complex
decarboxylation
oxidation of fatty acids produces what?
acetyl coa
-alternate source for TCA cycle
in one turn of tca, how many carboxyl groups are lost as co2? which steps?
2
step 3 and 4
carbons lost as co2 come from?
oxaloacetate, NOT acetyl coA
acetyl coA carbons become…
oxaloacetate of next turn
in tca, what is the final e acceptor in the rxn catalyzed by succinate dehydrogenase?
FADH2
amphibolic
anabolic and catabolic
tca cycle
in complete oxidation of glucose, how many atp andco2 made?
6co2
30 atp + 2 from gtp = 32 atp under max conditions
why is decarboxylation reaction easier for beta ketoacids?
resonance stabilized
which is unstable after decarboxylation: alpha or beta ketoacids?
alpha ketoacid
(pyruvate)
—unstable carbanion, no resonance, no e sharing
net reaction for pdc
2 pyruvate +2NAD+ + 2CoASH –> 2 acetyl coA + 2 NADH +2CO2
what fixes the problem of pyruvate as an alpha ketoacid?
pyruvate dehudrogenase complex
it catalyzes the oxidation ofpyruvate to acetyl coA using thiamine pyrophsphate (TPP)
beri beri
wet v dry
thiamine deficiency
wet –> cv system
dry –> nervous system
who is at risk for thiamine defficiency?
alcoholics and those with low nutritional intake
reactive center in TPP?
thiazole ring
polyneuropathy parasthesia paresis(partial paralysis/weakness) psychiatric edema
thiamine deficiency symptoms
three enzymes of pdc
e1 - pyruvate decarboxylase
e2 - transacetylase
e3 - dihydolipoyl dehydrogenase
cofactors of e1 - pyruvate decarboxylase
TPP
cofactors of e2 - transacetylase
lipoic acid and coenzyme a
cofactors of e3 - dihydrolipoyl dehydrogenase
FAD and NAD+
three steps of TPP decarbxylation of pyruvate?
- proton abstracted from thiamine by base creating tpp carbanion
- carbanion attacks carbonyl of pyruvate forming covalent intermediate
- co2 removed creating a beta ketoacid
pdc reaction is…
-8 kcal.mol –> irreversible and favorable
pdc is regulated by..
phosphorylation and dephosphorylation at a serine residue
- -dephosphorylated pdc is ACTIVE
- kinase adds P, inactivating complex
- Ca2+activates phosphatase –> turns PDC on
neurodegenerative disorder
pediatric onset, weakness, hypotonia, ataxia, spasticity, dyspnea, opthalmoplegia, optic atrophy
maternal, xlinked, auto recessive (all lethal)
leigh syndrome
how many atp is an NADH, gtp, and FADH2 worth?
nadh = 2.5 atp fadh2 = 1.5 atp gtp = 1 atp
coenzyme a in the pdc
part of transacetylase rxn
accepts acetyl group from acetyl lipoamide
between alpha ketoglutarate and malate, how many net ATP can be generated?
5
glucose to lactate versus complete oxidation atp production?
lactate conversion gives us 2 atp and complete oxidation gives 30-32…15x as great
three ways pdc can be activated
- ca2+ activates phosphotase
- inhibition of a kinase by pyruvate
- decrease NADH/NAD+ ratio
why does tca only run under aerobic conditions?
oxidized cofactors NAD and FAD are required for the oxidation reactions so aerobic conditions are needed to allow nadh and fadh2 to transfer their e into the ETC and regenerate nad and fad
anaplerotic reactions…
are necessary because the biosynthesis of some aa require tca intermediates as precursors AND
can convert pyruvate to oxaloacetate in mmmals
what requires biotin as a cofactor?
pyruvate carboxylase
glut =
5C
what keeps the tca cycle turning?
free energy of reactions, mainly -G (step 1 is -7.7, 3 is -5.3, and 4 is -8) so uphill last reaction to oxaloacetate is offset, and relative amount of NAD available
for every acetyl coa, how many oxaloacetates are made?
none!
used in next round of cycle
if citrate builds up, what enzyme is inhibited?
citrate synthase
what aa precursor can make more oxaloacetate?
aspartate
what aa can feed right into alpha ketoglutarate?
glutamate
succinyl coa can be replaced w …
3c propionyl coA from fatty acids
when and where is fat synthesized?
in cytoplasm when citrate builds up due to excess acetyl coA
