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40 Cards in this Set

  • Front
  • Back
Where does de novo fatty acid synthesis occur?
Where does elongation of existing fatty acids take place?
Where does desaturation of fatty acids occur?
endoplasmic reticulum
How does the Acetyl-CoA needed for fatty acid synthesis get from the mitochondria where it is formed to the cytoplasm?
Acetyl CoA can't cross the mitochondrial membrane, but citrate can. Citrate is broken down into Acetyl-CoA and OAA by citrate lyase.
What is the rate limiting step in de novo fatty acid synthesis?
The conversion of Acetyl-CoA to malonyl CoA by Acetyl CoA carboxylase using 1 ATP, CO2 and a biotin cofactor.
What reducing cofactor is used in de novo fatty acid synthesis? How is it's levels maintained in the cytoplasm?
NADPH, Citrate -> OAA -> malate -> pyruvate + NADPH
What inhibits Acetyl CoA carboxylase?
palmitoyl CoA, phosphorylation by cAMP mediated protein kinases
What stimulates Acetyl CoA carboxylase?
What is the effect of glucagon on fatty acid synthesis?
inhibits fatty acid synthesis
What is the effect of glucagon on beta oxidation? How?
stimulates beta oxidation because it inhibits the formation of malonyl CoA which inhibits the carnitine palmitoyl transferase 1 needed for beta oxidation
What enzymes are part of Fatty acid Synthetase complex (FAS)?
acetyl transferase, malonyl transferase, beta-ketoacyl synthetase, beta-ketoacyl reductase, dehydratase, enoyl reductase
What enzyme transfers acetyl CoA to the FAS complex?
acetyl transferase
What enzyme transfers malonyl CoA to the ACP-sulfhydryl on the FAS complex?
malonyl transferase
What is an ACP?
acyl carrier protein
What does beta-ketoacyl synthetase do?
transfers the acetyl group on FAS to the alpha carbon of malonyl CoA on ACP displacing CO2
What does beta-ketoacyl reductase do? What cofactor does it use?
reduces the beta carbon producing beta hydroxybutyryl-S-ACP and oxidizing NADPH to NADP+
What enzyme creates a double bond between the alpha and beta carbons of beta hydroxybutyryl-S-ACP?
What enzyme reduces the carbon double bond created by the dehydratase enzyme in fatty acid synthesis? Does it require a cofactor?
Enoyl reductase, oxidizes NADPH to NADP+
What is the last step in de novo fatty acid synthesis? What enzyme catalyzes it?
a transferase shifts the newly formed acyl from the Sulfhydryl of ACP to the sulfhydryl of FAS, freeing it to accept another malonyl CoA molecule and continue elongation
What is the longest fatty acid carbon chain that can be created by de novo fatty acid synthesis?
Palmitic Acid (16:0)
What does deacylase do?
it removes the newly synthesised fatty acid from FAS so that FAS can be reused to synthesize more FAs
How many CO2 are consumed to synthesize palmitic acid by de novo fatty acid synthesis?
7 CO2 (one for every malonyl CoA formed and added to the growing fatty acid)
How many NADPH are consumed per malonyl CoA added to the fatty acid chain?
Which step of de novo fatty acid synthesis requires ATP?
the formation of malonyl CoA from acetyl CoA via acetyl CoA carboxylase
Name three pathways that generate NADPH.
pentose phosphate pathway, isocitrate dehydrogenase, malic enzyme (malate -> pyruvate)
Why does C75 Cerulenin drug inhibit hunger?
it inhibits the fatty acid synthetase complex, thereby causing a buildup of malonyl CoA qhich either inhibits neuropeptide Y or other neuropeptides that stimulate hunger sensation in the brain
fatty acid elongation in the mitochondria uses what precursor and adds what compound to it?
starts with palmityl CoA and adds acetyl CoA
Name the four enzymes involved in fatty acid elongation in order.
thiolase, dehydrogenase, hydratase, dehydrogenase (reverse of beta oxidation pathway)
the dehydrogenases in fatty acid elongation use what cofactor?
NADPH (it gets oxidized)
fatty acid elongation in the ER uses which compound as the 2 carbon donor?
malonyl CoA
What reaction does thiolase catalyze in fatty acid elongation?
The transfer of palmitoyl CoA onto the alpha carbon of acetyl CoA.
Under what conditions does fatty acid elongation occur?
in the fed state
why are linoleic and linolenic acids essential?
because the mixed function oxidase used in the desaturation of fatty acids in the ER cannot add a double bond beyond the 9-10 carbons of fatty acids
what enzyme adds double bonds to saturated fatty acids in the ER?
mixed-function oxidase called desaturase
does desaturase use a cofactor? which one?
it oxidizes NADPH to NADP+
what kind of double bond does desaturase create?
what is the precursor of arachidonic acid?
linoleic acid
what is the precursor of docosahexaenoic acid?
linolenic acid
what pathway uses arachidonic acid as a substrate?
prostaglandin synthesis
what is docosahexaenoic acid used for?
neuronal synapses and retinal photoreceptors