Membrane Lipids

The main classes of membrane lipids are phospholipids, glycolipids, and sterols.

Phospholipids are the most abundant type of lipid in membranes, specifically phosphoglycerides.
The kind and relative proportion of different lipids varies between different membranes. For example:
- Rat liver cell plasma membrane: Contains phosphatidylethanolamine, phosphatidylcholine (highest amount), phosphatidylserine, sphingomyelin, phosphatidylinositol, and phosphatidylglycerol.
- Potato plasma membrane: Mainly phosphatidylethanolamine, phosphatidylcholine, and phosphatidylinositol.
- E. Coli: Different combinations.

The most common glycolipids found in membranes are cerebrosides and gangliosides.
Difference between cerebrosides and gangliosides:
- Cerebrosides are neutrally charged.
- Gangliosides are negatively charged.
Both are prominent in neurons.
- Problems with their metabolism or removal can cause nervous system issues.
Gangliosides Function as Blood Type Antigens:
- Blood types (A, B, AB, O) are determined by the type of ganglioside on the red blood cell membrane.

A lysosomal storage disease caused by impaired metabolism of gangliosides.
Gangliosides accumulate in cells due to a mutation in the enzyme responsible for breaking them down.
Affects the nervous system due to the high concentration of gangliosides in neurons.
Symptoms:
- Normal at birth, followed by progressive nervous system deterioration.
- Usually lethal, with death occurring around three years of age.

Eukaryotic cell membranes contain cholesterol.
- Functions:
  - Stabilizes and maintains cell membranes.
  - Helps maintain membrane fluidity.

The length of the fatty acid chain determines membrane thickness.
An optimal length of 16-18 carbons is generally suitable for bilayer formation.
Membrane thickness can vary between different cellular locations (e.g., plasma membrane, ER membrane, Golgi membrane).