Synthesis of Membrane Lipids

1. Synthesis of Membrane Lipids
Vignesh. O

2. Membrane Lipids
• Lipids involved in forming the structure of biological membranes.
• Assembled from phosphoglycerides, sphingolipids and steroids.
• Arranged in bilayers.
• Amphipathic molecules.

3. Synthesis
• Occurs in endomembrane compartment (incl. the domain of golgi and ER).
• Specialized phospholipids are synthesized in mtc and peroxisomes.
• Includes the activity of hundreds of enzymes.
• Active transport (free diffusion denied due to hydrophobicity).

4. Phosphoglycerides
• Most abundant class.
• Derivatives of glycerol-3-phosphate.
• Contains 2 fatty acyl chains (esterified to -OH) and
polar head group(attached to phosphate).
• Classified according to head group.
Eg: Phosphatidylcholine (Lecithin) – Choline head group.
Phosphatidylethanolamine (Cephalin) – Ehanolamine head group.

8. Plasmalogens
• Phosphoglycerides with ester and ether linkage.
• Ester linkage (C-OOC) between fatty acyl group and glycerol.
• Ether linkage (C-O-C) between long HC chain and glycerol.
• Constitute 20% of phosphoglycerides.

9. Sphingolipids
Compounds derived from sphingosine (aminoacyl alcohol).
Eg. Sphingomyelin (phosphocholine attached to terminal hydroxyl group)
- Most abundant sphingolipid

10. Gangliosides
• Complex glycosphingolipid.
• Contains 1 or 2 sugar chains attached to sphingosine.

11. Steroids
• Cholesterol and derivatives.
• Steroid nucleus.
• Cholestrol abundant in plasma membranes of mammalian cells
but absent in prokaryotes.
• Amphipathic (Since –OH group interact with water)

12. Synthesis of membrane lipids
Why?
• Cells can’t divide and enlarge.
• Important as protein synthesis and DNA replication.
• Synthesize new membrane by the expansion of existing membranes.
• Early synthesis occurs in the cytoplasm.
• Final steps are catalyzed by pre-existing membrane bound enzymes.

14. • Fatty acids are the key components of membrane lipids

19. Fatty acids are the key components of membrane lipids
FA synthesis regulation plays major role in membrane synthesis also.