Sphingo Phospholipids

• Major class of phospholipids with a sphingosine backbone (not glycerol).
• Fatty acid attached by amide linkage to sphingosine, forming ceramide.
• Primary hydroxyl group esterified to phosphorylcholine (attached to phosphoric acid at carbon 3).
• Sphingomyelin
• Predominant in myelin sheaths, insulating axons in neurons (like insulating plastic around wires).
• Structure: contains ceramide, phosphoric acid, and choline.

Glycolipids

• Widely distributed in tissues, particularly nervous tissues (e.g., brain).
• Major type is glycosphingolipids, containing ceramide and one or more sugars (e.g., galactosylceramide).
• Galactosylceramide example: contains sphingosine, a 24-carbon fatty acid (cerebronic acid), and galactose.
• Can convert to sulfatide (sulfogalactoceramide by adding a sulfate group).

Gangliocytes

• Complex glycosphingolipids derived from leukocyte ceramide.
• High concentration in nervous tissues, function as receptors.
• Example: GM3 ganglioside contains ceramide, glucose, galactose, and N-acetyl neuraminic acid (NANA).
• GM1 is more complex, serves as a receptor in the intestine for cholera toxin.

Lipoproteins

• Transport insoluble lipids in blood.
• Composed of a non-polar lipid core (triglycerides, cholesterol esters) surrounded by phospholipids and proteins, making them water-miscible.
• Difference between free cholesterol (unesterified) and cholesterol esters (esterified for storage).
• Orientation in lipoproteins faces polar heads outward to interact with aqueous medium similar to cell membranes.