Biochem 406 lecture 3: transport and mobilization of fats

Where do chylomicrons transport fats (TG and CE)?

From the intestine to other tissues

Why are TAG resynthesized

TAGs are resynthesized from free fatty acid chains that are transported into tissues. By converting free fatty acyl chains to TAG you can create energy for later use

What are lipoproteins?

large complexes of lipids and proteins.

Inside there are TAGs and cholesteryl esters

Outside is a phospholipid monolayer and apolipoproteins

what are apolipoproteins

proteins that target the lipoprotein to specific tissue

what's a key difference in the role of chylomicrons and VLDLs

chylomicrons are assembled in the intestine and VLDLS are assembled in the liver. Both deliver energy to peripheral tissue

What do lipoprotein lipases do

Lipoprotein lipases break down lipoproteins into free fatty acids and glycerol

which class of plasma lipoproteins have the lowest density

Chylomicrons

what are the properties of chylomicrons

Density: <0.95 g/ml (lowest density)

Apolipoprotein: B48, C, E

Role: Transports dietary fat

what are the properties of VLDL

Density: 0.95-1.006 g/ml

Apolipoprotein: B100, C, E

Role: Transports fats made within the body

what are the properties of IDL

Density: 1.006-1.019 g/ml

Apolipoprotein: B100, E

Role: LDL precursor

What are the properties of low density lipoprotein

Density: 1.019-1.063 g/ml

Apolipoprotein: B100

Role: Cholesterol transport (to muscle)

what are the properties of HDL

Density: 1.063-1.21g/ml

Apolipoprotein: A

Role: Reverse cholesterol transport (muscles to liver)

what is the signal for the mobilization of stored fats

Glucagon is the signal for fasting, low energy state. It binds to a GPCR and stimulates cAMP production and PKA activation

How does the glucagon signal initiate fat mobilization

Glucagon signaling activates PKA

Activated PKA phosphorylates perilipins

Phosphorylated perilipins allows HSL to break down TAG in lipid droplets

What does Serum Albium

once mobilized, fatty acid chains are transported in the blood by binding to serum albium

What are the 3 steps for cells to use fats for energy production

1. Activation to fatty-acyl-CoA

2. Transport into Mitochondria

3. B-oxidation to produce NADH, FADH2, and Acetyl-CoA

How is fatty acid transported to the mitochondria

1. Fatty acid is activated when acyl-coA synthase adds acetyl CoA to fatty Acyl chain

2. Fatty acyl-coA is converted to fatty acylcarnitine by acyltransferase 1 (CAT 1)

3.Acyl carnitine translocase moves fatty acylcarnitine to the mitochondria

4. Carnitine acyltransferase II (CAT II) converts fatty acyl carnitine back to fatty acyl-coA

How many carbons does each round of Beta oxidation remove, and what are products generated

Each round loses two carbons

Produces, 1 NADH, 1 FADH2, and 1 Acetyl CoA

What is step 1 of Beta oxidation

Oxidation converting acetyl-coA to Enoyl-CoA

what is step 2 of Beta oxidation

Hydration converting enoyl-CoA to B-hydroxy acyl CoA

what is step 3 of beta oxidation

oxidation turning the hydroxy group on the beta carbon into a ketone turning B-hydroxy acyl CoA into B-ketoacyl-CoA

what is step 4 of beta oxidation

Thiolysis forming acetyl CoA and a shortened acyl-coA

For 1 molecule of Palmitoyl-CoA how many acetyl-CoA would be produced for TCA

8 acetyl-coA

What are the key enzymes for B-oxidation of fatty acid for poly unsaturated fatty acids

2,4, Dienoyl-CoA reductase and enoyl-CoA isomerase (which turns cis to trans bonds)

What enzymes are additionally need for odd chain fatty acids

Propionyl CoA carboxylase (+biotin cofactor) adds a CO2 to remaining acetyl coA

Methyl malonyl CoA mutases (+B12 cofactor) rearranges the C-C bonds to make succinyl CoA