module 9- Fatty acid synthesis Flashcards
location of fatty acid synthesis
cytosol
ATP-citrate lyase
cleaves citrate into acetyl CoA & oxaloacetate
what enzyme catalyzes acetyl CoA + oxaloacetate -> citrate
citrate synthase
oxaloacetate is reduced using?
NADH
malic enzyme
malate -> pyruvate
pyruvate fate
back to mitochondria to make more acetyl CoA
how is acetyl CoA activated
by converting it to malonyl CoA
acetyl CoA carboxylase
acetyl CoA -> Malonyl CoA
what enzyme contains biotin group
acetyl CoA carboxylase
palmitate
16 carbon saturated fatty acid, synthesized via 4 reactions
fatty acid synthase complex
large enzyme system that synthesizes fatty acids
fatty acid synthase complex in plants vs yeast vs vertebraes
plants- made of individual proteins
yeast- made of 2 polypeptides
vertebrates- made of 1 polypeptide
acyl carrier protein (ACP)
has phosphoantetheine group, acts as an arm to synthesize palmitate
odd chain fatty acids begin with ( ) and even chain ( )
propionate, accetyl CoA
4 steps of FA synthesis & their enzymes
1) condensation- B-ketoacyl synthase
2) reduction- b-ketoacyl reductase
3) dehydration- 3-hydroxyacyl dehydratase
4) reduction- enoyl reductase
in order to complete the synthesis of a free fatty acid, ( ) must be released from ACP
palmitate
what enzyme produces palmitate at the last step of FA synthesis
thioesterase
how many molecules of NADPH are required for 1 FA synthesized?
14
for every acetyl CoA brought into the cytosol, ( ) molecule of NADPH is also produced
1
how many molecules of acetyl CoA & NADPH to make palmitate
8, 8
where do the other 6 molecules of NADPH for palmitate synthesis come from?
pentose phosphate pathway
T or F: tumors high have need for FA
T
what enzyme can be used to inhibit tumors
B-ketoacyl ACP synthase
longer fatty acids are made by adding ( ) carbon-units to the carboxyl end using ( ) as the substrate
2, malonyl CoA
2 essential FA names
linoleate- 6
linolenate - 3
eicosanoids
local hormone signalling
how does aspirin work
promotes addition of an acetyl group to an amino acid in active site = inhibits enzymes
what is the regulator enzyme in FA synthesis
acetyl CoA carboxylase
when is FA synthesis the highest?
lots of carbs, little FA
what is the precursor for FA
acetyl CoA
how is acetyl CoA carboxylase regulated by? (2)
allosterically & covalent modifications
AMP-activated protein kinase (AMPK)
phosphorylates acetyl CoA carboxylase = inhibits it
under low conditions, acetyl CoA carboxylase would be ( ) by AMPK & inhibited
phosphorylated
under high conditions, acetyl CoA carboxylase is ( ) by phosphatase 2A & activated
dephosphorylated
how is acetyl CoA carboxylase allosterically activated by citrate?
high citrate = lots of substrates for FA synthesis
what form of acetyl CoA carboxylase is a dimer of identical subunits?
inactive form (phosphorylated)
T or F: citrate can partially reverse the inhibition caused by phosphorylation of MIG12
T
what induces polymerization of dimers? what induces depolymerization?
citrate, palmitoyl CoA
acetyl CoA carboxylase & FA synthesis is stimulated by?
insulin
when is insulin high?
after a meal
insulin causes the activity of acetyl CoA to increase by ( ) AMPK & ( ) phosphatase 2A
inhibiting, stimulating
net shift of acetyl CoA carboxylation
most will be in active form
glucagon & epinephrine ( ) FA synthesis
inhibit
desaturation
removal of 2 hydrogen atoms with the creation of a double bond
FA synthesis takes place in () stages
3
how many sources provide the required NADPH for FA synthesis
2- acetyl CoA transport & pentose phosphate pathway
T or F: additional enzymes elongate & desaturate FA
T
