Phosphoglycerides

Phosphoglycerides

• Main type of lipid found in membranes and present in the highest quantities.
• Structure:
  • Glycerol backbone.
  • One carbon has a phosphate group with an R group.
  • The other two carbons have fatty acid chains attached.

Phosphatidic Acid

• The basis of phosphoglycerides, referring to the components mentioned above.
• Fatty Acid Chains:
  • Typically, one fatty acid chain is saturated, and the other is unsaturated.
  • Commonly, the fatty acid chains consist of either 16 or 18 carbons.

Membrane Importance

• Triglycerides are for fat storage, not for membrane structure.
• Illustration of membrane structure:
  • Phosphates with tails (fatty acid chains).
  • Lipids arranged to form a bilayer.

Membrane Considerations

• Thickness/Width:

  • The width of the membrane is critical because proteins embedded in the membrane have hydrophobic spans of a specific length.
  • The length of the fatty acid chains (16-18 carbons) dictates the correct membrane width to match the hydrophobic spans of the proteins.

• Membrane Fluidity:

  • Membranes need to be pliable to allow channels to open and close.
  • Lipids must be able to "give" when channels change shape to move substances in and out of the cell.
  • Having one saturated and one unsaturated fatty acid chain helps regulate membrane fluidity.
    • Saturated chains pack tightly.
    • Unsaturated chains introduce kinks, providing space and flexibility for movement.

R Groups

• The R group attached to the phosphate is typically a small alcohol, contributing to polarity.

• Common Alcohol Groups:

  • Serine
  • Ethanolamine
  • Choline
  • Inositol

These alcohols are frequently found as part of phosphoglycerides, influencing their properties and interactions within the membrane.