Membrane Lipids

Membrane Lipids

1. Ampipathic: Contain both hydrophilic and hydrophobic regions

   • 3 types: Phosphoglycerides, sphingolipids, chloesterol

2. Phosphoglycerides

   • Contain a GLYCEROL BACKBONE and a PHOSPHATE GROUP
     • Only two of the hydroxyl groups of the glycerol are esterified to fatty acids
       • Fatty acyl chains are hydrophobic and unbranched. May be fully saturated, monounsaturated (one double bond), or polyunsaturated.
         • Phosphoglyercides may contain one unsaturated and one saturated fatty acyl chain.
     • A hydrophilic group linked to the phosphate. (Small and hydrophilic). Either choline, ethanolamine, serine, or inositol.
       • Phosphate together with hydrophilic group form a highly water-soluble domain at one end of the molecule, called the head group.
         • Phosphate+choline (PC) and Phosphate-Ethanolamine (PE) are NEUTRAL.
         • Phosophate-Serine (PS) and Phosphate-Inositol (PI) have an overall NEGATIVE charge.

3. Sphingolipids

   • Derivatives of sphingosine, which is an animo alcohol that contains a long hydrocarbon chain.
     • Consist of sphingosine linked to a fatty acid by its amino group
       • Additional groups esterified can to the terminal alcohol
         • Sphingomyelin
         • Glycolipid
           • Crucial roles in cell function
           • Nervous system is rich in glycolipids
             • Makes up the myelin sheath
               • Not having glycolipids can result in: Severe muscular tremors, paralysis, severe seizures, blindness
         • Cerebroside

4. Cholesterol

   • In certain animal cells, may constitute up to 50 percent of the lipid molecules in the plasma membrane.
     • Plant cells contain cholesterol-like sterols, but it is unknown whether they contain real cholesterol.
   • Oriented with their small hydrophilic hydroxyl group toward the membrane surface and the remainder of the molecule is in the lipid bilayer
     • The hydrophobic rings are flat and rigid, and they interfere with the movements of the fatty acid tails of the phospholipids.

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