Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
40 Cards in this Set
- Front
- Back
Where does de novo fatty acid synthesis occur?
|
cytoplasm
|
|
Where does elongation of existing fatty acids take place?
|
mitochondria
|
|
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?
|
citrate
|
|
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?
|
dehydratase
|
|
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?
|
2 NADPH
|
|
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?
|
cis
|
|
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
|