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Biochem High Points: Lipid Metabolism


How many ATP are yielded from complete oxidation of one 16 carbon fatty acid?
129
fats = 9 Kcal/gram

What's the key enzyme in lipolysis?
carnitine acetyltransferase

What's the key enzyme in lipid synthesis?
acetyl CoA carboxylase

What's the key enzyme of fat mobilization?
hormone sensitive lipase

What do you call the cleavage of the fatty acid at the carboxyl end to form the 2 carbon acetyl coA molecule?
beta oxidation
CPT-1-->acyl units delivered into mito for beta oxidation
acyl-coA-->acetyl coA called beta oxidation


What does acetyl coA turn into in the citric acid cycle?
co2 and energy! and water?? and ????

What's HMPS?
hexose monophosphate shunt
pentose pathway
3 interconnected cycles in which glucose 6-phosphate is the substrate and end product
rxns leading to ribulose-5-phosphate are irreversible, the rest are reversible
NADPH & ribose-->F6P

CHO-->Acetyl CoA-->Malonyl CoA-->Palmitate
What is the enzyme that converts Acetyl CoA-->Malonyl CoA?
Acetyl CoA Carboxylase

Where does all this happen?
in the cytosol

What hormone increased Acetyl CoA Carboxylase action?
insulin

Malonyl CoA inhibits CPT-1 function???
Acyl units contribute to CPT-1 function???
What is CPT-1?
a transporter that brings acyl CoA into the mitochondrion?


Acyl units aka fatty acids become what when they are esterified?
TG's

Where do TG's go from the cytosol?
into the blood

ffa-->acyl coA via acyl coA synthase
acyl coA-->acetoacetyl coA via beta oxidation
acetoacetyl coA-->acetyl coA via a thiolase, goes both ways
acetoacetyl coA can also-->HMG-coA via HMG coA synthase

Can you make acetyl coA from HMG-coa?
yes
can go HMG coA-->acetyl coA-->acetoacetyle coA-->back to HMG coA

What are the two other major products made from HMG-coA?
cholesterol, ketone

What enzyme is inhibited by statins?
HMG-coA REDUCTASE
HMG-coA-->mevalonate

What three products are made from mevalonate?
co-Q10
dolichol
squalene

Which one of these products is part of cholesterol synthesis?
squalene
HMG-coA-->mevalonate-->squalene-->desmusterol-->cholesterol

What is the enzyme for the last step to cholesterol?
alpha? delta? 24 reductase

Which compounds can be converted to ketones?
HMG-CoA-->acetoacetate-->ketone = D(-)-3-hydroxybutyrate

What enzyme converts HMG coA to acetoacetate?
HMG coA lyase (I think it makes both acetyl coA and acetoacetate)

What is acetoacetate good for?
brain fuel

What enzyme converts acetoacetate to ketone?
ketone dehydrogenase

What enzyme breaks TG's down to fatty acids?
lipoprotein lipase in liver
also hormone sensitive lipase in adipose (epi and cortisol incr, insulin decr action)

What is LPL?
lipoprotein lipase
makes glycerol in plasma and FFA in adipose or muscle
from VLDL and chylomicrons full of TG's

Where does lipogenesis take place?
liver

Where does ketogenesis take place?
liver



Where does beta oxidation take place?
muscle

What can you make out of glycerol?
TG's if you add fa's

What does thiokinase make?
acyl coA from acyle, ATP and coA-Sh (Sh and AMP and 2pi released)

How do acyl-coA's get into the mitochondria?
CPT-1

What is CPT-1?
carnitine palmitoyl transferase I

What is VDAC?
looks like it's a prot that forms the pore through the outer mito membrane

What's CPT-II?
transporter in inner mito membrane, gets acyl-coA in
carnitine is attached to acyl group when it travels between inner & outer membranes
is recycled when acyl group dropped off at inner


Name the enzyme that attaches the coA to the acyle group.
thiokinase
aka acyl coA synthase
not sure where the sulfur goes but it is in acyl coA and lost with acyl-carnitine
so coA must have sulfur in it

oh yes it does, aka coAsh for the sulfhydryl

Where are TG's broken to acyl groups and connected to coA?
in cytosol

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