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Biochem weightloss FA synthesis 1


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FA metabolism makes Fatty acids for what molecules (list structure)
Triacylglycerols (3FA + glycerol backbone)(main E)

Phospholipids ( 2FA + phos'd glycerol)

Cholesterol ester (1FA + steroid ring)
Where does FA come from? / is degraded back down to?
Acetyl CoA
For structure see page 62
how long are:
s - 2-6 C
m - 6-12
l - 14-20
verylong - 22 and up
is a cis or trans dbl bond a kink?
how far apart must dbl bonds be?
at least 3 C's apart
which carbon in linoleic acid is C1, carboxy end or methyl end
the carboxy carbon
palmitic acid
palmitoleic acid

16: 1 delta9
stearic acid
oleic acid
linoleic acid
Alpha-linolenic acid
stearic: 18:0

oleic: 18:1 delta9

Linoleic: 18:2 delta 9,12

alpha-linoleic: 18:3 delta 9,12,15
arachidonic acid
20:4 delta 5,8,11,14
which ones are in the omega-6 family?
linoleic and arachidonic acid
which are omega-3?
omega-3: alpha-linolenic

omega-7: palmitoleic
where does FA synthesis occur
cytosol (liver adipose CNS and mammary)
overall reaction of FA synthesis
8 acetyl CoA


palmitate 16:0

CoAsh, NADP and water
FA synthesis
exergonic vs endergonic
reductive vs oxidative
endergonic and reductive
Acetyl CoA
acetyl group - long flexible phosphopantetheine group - Ribose - adenine
panothenic acid, how synthesized in humans
not, its an essential nutrient
Acetyl CoA carboxylase

what it does
AcetylCoA + CO2 + ATP --> malonyl CoA + ADP + Pi

BIOTIN as a co-enz PROSTHETIC GROUP (cov bound) swinging arm binds CO2 like in pyruvate carboxylase of gluconeogenesis
Acetyl CoA carboxylase

importance of the step it catalyzes

allosteric effectors (+and-)
makes malonyl CoA in a committed rate limiting irrev step

Allosteric effectors:
+ citrate
- palmitic acid (end product)
Acetyl CoA carboxylase

covalent regulation

what causes a positive allosteric effect or a negative allosteric effect
inactive when phosphorylated

deP'd when insulin is high (insulin/glucagon ratio is high)
P'd when glucagon is high by AMPK (in assoc with PKA)
Fatty acid synthase

catalyzes malonyl CoA and Acetyl CoA to palmitate

7 catalytc activities and an ACP carrier protein domain
ACP domain
has a posphopantetheine group like in acetyl CoA, uses this swinging arm to link intermediates
Describe/ draw out FAS activity
Tranferase: takes malonyl CoA and Acetyl CoA and makes malonyl-s-ACP and acetyl s-ACP

combine the two using condensing enzyme (CO2 leaves)

Reduce - beta-ketoacyl reductase (uses NADPH)

Dehydrate (dbl bond between alpha and beta C): beta-Hydroxylacyl dehydratase

Reduce - transenoyl reductase (uses NADPH)

repeatedly combine with malonyl-s-ACP till you get palmitoyl-s-ACP (16:0)

cleave off s-ACP using thioesterase
if you use methylmalonyl CoA instead of malonyl CoA what happens
you make branched chain FA
explain transport of Acetyl CoA out of mito and into cytosol where FA synthesis occurs
Acetyl CoA + OAA --> citrate
via citrate synthase

citrate is shuttled out

citrate -->Acetyl CoA and OAA
via Citrate lyase

OAA --> malate via malate DeH

malate goes into mito and this drives the malate citrate transporter, once in mito malate is converted back to OAA (which can then combine with acetyl CoA to make citrate)
Refresher how does pyruvate get into the mito?
proton pyruvate symporter, uses inter membrane proton gradient
where else can you get a source of NADPH (remember you use two per addition of malonyl) besides pentose pathway?
malate + nadp --> pyruvate + NADPH

via malic enz
oxidative portion of pentose pathway
G6P -(DeH)-> lactone -(lactonase)-> glucontate -(DeH)->

ribose-5-p + CO2 + 2NADPH
How does elongation of DIETARY FA differ from de novo?
more than one enz
ER bound!
CoA (not ACP)
Substrates are over 10C long
How many NADPH does de NOVO syn take to make palmitoyl?
in dietary elongation how many NADPH per C added?
1 nadph per C (like in de novoe)
Where are the C from malonyl CoA added into dietary FA?

at carboxy carbon
Question on counting the C's in FAsynthase, follow the C's from malonyl and acetyl, where is alpha beta, where does dbl bond insert
Desaturation of dietary FA
insertion of dbl bond, uses :

cytochrome b
NADH cytochrom b reductase

Where can humans place dbl bonds
at 9, 6, 5, and 4 (the four types of desaturases)
where is the limit of desaturation in humans
cannot insert beyond C10
What family of FA's can humans not synthesis
omega-6 and omega-3
how do you make arachidonic acid from linoleic? (omega-6)
linoleic 18: delta 9,12

desat at 6 (three C's away)

elongate to 2 C's (pushes dbl bonds further away from C1)

Desaturate at 5

get 20:4 5,8,11,14

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