B2 Fatty Acid Storage + Mobilization

Where are chylomicrons formed? VLDLs?

1. In the small intestine

2. In the liver

Describe the process of storing lipids from a chylomicron/VLDL in the bloodstream

1. The CM or VLDL get broken down by LPL (lipoprotein lipase)

   1. The glycerol group goes to the liver

2. The free fatty acids are carried by FABP (fatty acid-binding protein) to get activated at the FACS (free acyl CoA synthase)

3. The fatty acids turn into Acyl-CoA

4. the acyl cleaves off and binds with a glycerol (from glycerol phosphate) and create new triglycerides

Describe the mobilization of fatty acids from ADIPOCYTES

1. HSL initiates the breakdown of triglycerides into glycerol (which goes off to the liver) and free fatty acids

2. Free fatty acids are then transferred by FABP (fatty acid binding protein) to the bloodstream, first passing through the membrane

   1. Fatty acid translocase (FAT) is present at the plasma membrane and it helps the fatty acids cross the membrane

3. Albumin takes up the free fatty acids in the blood stream and takes ‘em to the liver to create more fuel

Describe the mobilization of fatty acids from SKELETAL MUSCLE

Three different processes occurring at once

1. HSL stimulating the breakdown of fatty acids into FFA and glycerol

2. FABP taking the three fatty acids off albumin and taking it to the fatty-acid CoA synthase

3. Chylomicrons or VLDLs breakdown by LPL to create FFA which are then transferred to the the fatty-acid CoA synthase by FABP

How does acyl-CoA cross into the mitochondria from the cytosol?

The carnitine shuttle

Describe the process of carnitine shuttling

• Carnitine acyltransferase 1 (CAT-1) turns Acyl-CoA into Acyl-carnitine so it can be transferred through the outer membrane into the intermembrane space (CoA is too large to traverse the outer membrane)

• Carnitine acyltransferase 1 (CAT-2) turns acyl-carnitine back into acyl-CoA to be transferred into the matrix for beta-oxidation

What are the two REDOX reactions in beta oxidation? What are their products?

1. Acyl-CoA dehydrogenase

   1. Acyl-CoA is oxidized

   2. FAD⁺ → FADH₂ (reduced)

2. L-3-hydroxyacyl CoA dehydrogenase

   1. L-3-hydroxyacyl CoA is oxidized

   2. NAD⁺ → NADH (reduced)

   3. produces Acetyl-CoA

What reaction forms acetyl coa?

L-3-hydroxyacyl CoA dehydrogenase

• electron goes to NAD

What reaction breaks down acyl-coa

Acyl-CoA dehydrogenase

• electron goes to FAD+