PHOSPHOLIPIDS, GLYCEROPHOSPHOLIPIDS, SPHINGOMYELIN AND GLYCOLIPIDS

PRESENTED BY: AYESHA KABEER
FROM: UNIVERSITY OF GUJRAT SIALKOT SUBCAMPUS
1. PHOSPHOLIPIDS
2. GLYCEROPHOSPHOLIPIDS
3. SPHINGOMYELIN
4. GLYCOLIPIDS

1. Phospholipids, Glycerophospholipids, Sphingomyelin, Glycolipids PRESENTED BY: AYESHA KABEER

2. Phospholipids are: major constituents of all cell membranes components of bile anchor some proteins in membranes signal mediators components of lipoproteins

3. Structure of phospholipids Phospholipids have two fatty acids that help form a diacylglycerol. The third carbon of the glycerol backbone is also occupied by a modified phosphate group However, just a phosphate group attached to a diacylglycerol does not qualify as a phospholipid. This would be considered a phosphatidate or phosphatidic acid (diacylglycerol 3-phosphate), the precursor to phospholipids. To qualify as a phospholipid, the phosphate group should be modified by an alcohol. Phosphatidylcholine and phosphatidylserine are examples of two important phospholipids that are found in plasma membranes.

4. Phospholipid

5. Properties of phospholipids Phospholipids are amphipathic molecules Head group = alcohol attached via phosphodiester linkage to either: diacylglycerol (glycerophospholipid) or sphingosine (sphingophospholipid = sphingomyelin).

6. Cellular membranes are composed of phospholipids and sphingolipids Glycerophospholipids and sphingolipids spontaneously self-associate in water to form bilayer vesicles (i.e., closed membranes) Bilayers are permeability barriers that enclose cells and cell organelles, and “dissolve” intrinsic membrane proteins

7. Glycerophospholipids Glycerophospholipids are the main class of phospholipids They are the main lipid component of cell membranes, and are important in the cell’s semipermeability They also interact with triacylglycerols and cholesterol to increase their solubility in the blood These abilities of glycerophospholipids are due to their amphipathic nature, with a polar head group and nonpolar tails Glycerol PO 4 Amino alcohol Fatty acid Fatty acid

8. Glycerophospholipids are similar to triacylglycerols, but have one ester bond replaced with an amino alcohol phosphate ester.i.e. Glycerophospholipid

9. Each glycerophospholipid includes a polar region: glycerol , carbonyl O of fatty acids, P i , & the polar head group ( X ) non-polar hydrocarbon tails of fatty acids ( R 1 , R 2 ).

10. Structure of a Glycerophospholipid

11. Lecithins and Cephalins Glycerophospholipids can be classified based on the amino alcohol group Two common types are lecithins (which contain choline) and cephalins (which contain ethanolamine) Lecithins and cephalins are highly abundant in brain and nerve tissues, and are also found in egg yolks, wheat germ and yeast

12. Phosphatidylinositol , with inositol as polar head group, is one glycerophospholipid. In addition to being a membrane lipid, phosphatidylinositol has roles in cell signaling.

13. The other one is cardiolipin. Cardiolipin is found in mitochondrial membrane.

14. Sphingomyelin Sphingomyelins are phospholipids that are based on the 18-carbon amino alcohol sphingosine , instead of on glycerol A fatty acid is linked to the amine group by an amide bond, and an amino alcohol phosphate ester is linked to the bottom hydroxyl group (the top hydroxyl group remains free) Sphingomyelin is the main component of the myelin sheath of nerve cells

15. In the more complex sphingolipids, a polar “head group" is esterified to the terminal hydroxyl of the sphingosine moiety of the ceramide.  The amino group of sphingosine can form an amide bond with a fatty acid carboxyl, to yield a ceramide .

16. Sphingomyelin, with a phosphocholine head group, is similar in size and shape to the glycerophospholipid phosphatidyl choline. Sphingomyelin has a phosphocholine or phosphethanolamine head group. Sphingomyelins are common constituent of plasma membranes.

17. Glycolipids(glycosphingolipids) Glycolipids are sphingolipids that have one or more monosaccharides linked by glycosidic bonds to the bottom hydroxyl of the sphingosine. In contrast to sphingomyelin they do not have a phosphocholine group.

18. Types of Glycolipids(glycosphingolipids) Cerebrosides have a single monosaccharide (usually galactose) - they are usually present at the cell surface, and are involved in cellular recognition and immunity

19. Types of Glycolipids(glycosphingolipids) Gangliosides have two or more monosaccharides, usually glucose and galactose - they are abundant in the cell membranes of neurons - they act at the cell surface as receptors for hormones

20. F unctions of glycolipids