L6: Lipids

Question 1

What property distinguishes lipids from other biomolecules

Answer 1

1. Insoluble in water / hydrophobic

2. Long HC chain

Question 2

Structure of lipid / Triacylglycerol

Answer 2

• 3 fatty acyl chain (1 unsaturated, 2 saturated) + glycerol

- ester linkage

Question 3

Classification of lipid

Answer 3

1. Neutral lipid (storage)
   - Triacylglycerol
2. Polar lipid / Amphiphile (membrane)
   - Phospholipid (Glycerophospholipid and Sphingolipid, form liposome)
   - Cholesterol (form bile salt, steroid hormones, lipoprotein, membrane, Vitamin D)
   - Glycolipid

Question 4

Components of chylomicrons

Answer 4

1. Phospholipid
2. Cholesterol (intercalated between phospholipid)
3. Apolipoprotein (from Rough ER)
4. TAG / Cholesteryl ester

Question 5

How is lipid transported in our body

Answer 5

1. Dietary TAG
2. Emulsification
3. Pancreatic lipase digestion (TAG —> 2 monoacylglycerol + FA)
4. Transcellular absorption
5. Reesterification in smooth ER to TAG, packaged with B-48 apolipoprotein from rough ER in Golgi apparatus —> Chylomicrons
6. Exocytosis
7. Travel in lymph —> blood —> muscle, adipose tissue + liver (remnants: for recycling of materials e.g. amino acids, cholesterol)
8. Lipoprotein lipase activated by ApoC2 —> digest TAG in chylomicron
9. FA either oxidised to yield ATP / re-esterified with glycerol for storage

Question 6

Beta oxidation of fatty acid

Answer 6

Fatty acid —(β oxidation)—> Acetyl CoA, NADH, FADH2