Lipid Metabolism

Describe Palmitic acid in terms of the number of carbons and double bonds
Palimitic Acid- 16:0
Describe arachidonic acid
20:4
What is a cerebroside?
A cerebroside is a ceramide with one sugar attached
What is a ganglioside?
A ganglioside is a ceramide with more than one sugar attached
What tissue cannot use fatty acids as a fuel?
Erythrocytes
What transports free fatty acids from the cytoplasm into the matrix?
The carnitine cycle
What is the difference between acyl-CoA and acetyl-CoA?
acyle-CoA is a long chain free fatty acid
acetyl-CoA is a 2 carbon fatty acid
What is the difference between acyl-CoA and acetyl-CoA?
acyle-CoA is a long chain free fatty acid
acetyl-CoA is a 2 carbon fatty acid
What are the products of one round of Beta Oxidation of fatty acids?
one round of beta oxidation produces 1 FADH2, 1 NADH and an Acetyl CoA (2 Acetyl-CoA’s if it’s the last round of an even numbered acyl-CoA)
What are the four repeated steps of beta oxidation?
1. dehydrogenation
2. hydration
3. dehydrogenation
4. cleavage
How are dietary fatty acids transported in the blood?
FA’s are transported via chylomicrons (lipoproteins). They are released by a LIPOPROTEIN LIPASE
Fatty Acids stored in adipocytes are released by hormone sensitive lipase. What hormones regulate this enzyme?
Glucagon (+)
Insulin (-)
How are fatty acids released from adipocytes transported in the blood?
When released from adipocytes they are bound to serum albumin in the blood
Free fatty acids (when really free) act like what, in the cell?
Actually *free* fatty acids act like detergents and are bad for cell membranes
Before fatty acids can be oxidized they must be ______ for reaction in an ATP dependant acylation reaction to fom _________
1. primed
2. acyl-CoA
Where does the ‘priming’ (conversion of FA to acyl-CoA) of fatty acids occur?
Fatty acids are primed- turned inot acyl-CoA- in the outer mitochondrial membrane, by ‘fatty acyl-CoA synthetase’
What makes the creation of acyl-CoA from fatty acid an irreversible reaction?
The cleavage of PPi to 2Pi drives the reaction forward
FAs are converted to acyl-CoA on the outer mitochondrial membrane. What is the mechanism for the acyl-CoA to cross the inner mitochondrial membrane?
transport steps:
1. carnitine acyl transferase I (CAT1) regulated step
2. Translocase
3. Carnitine acyl transferase II (CATII)

(note that the CoA does not actually cross the membrane, but is replaced by carnitine, and once the molecule crosses the border, is switched back to CoA)

List the four repeated steps of B-oxidation and the enzymes that catalyze them.
1. Dehydrogenation (acyl CoA dehydrogenase)
2. hydration (enoyl CoA hydratase)
3. dehydrogenation (B-hydroxy acyl COA dehydrogenase)
4. cleavage (B-ketothiolase)
What are the products of a completely B-oxidized palmitate (16C) molecule?
B-oxidation of palmitate would result in:
8 acetyl CoA
7 FADH2
7 NADH+H+
(and requires 7 cycles of oxidation)
The special case problem of an acyl-CoA with double bonds between carbons 3-4 (instead of the normal 2-3) can be resolved by what enzyme?
Enoyl CoA isomerase – can move the double bond from 3-4 to 2-3. (Also, it should be a trans double bond)
Polyunsaturated acyl-CoA (more than one double bond) requires which two enzymes?
It requires a reductase in addition to the enoyl CoA isomerase
Odd numbered carbon chains (ex. C17) require what special measures for oxidation?
1. The last round of B-Oxidation leaves a 3 carbon group called propionyl CoA
2. Propionyl CoA can be converted into succinyl CoA (and then enter the TCA cycle), but it requires ATP and vitamin B12. The enzyme used is methylmalonyl CoA mutase.
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