Phosphoglycerides (phospholipids) are the major structural components of the cell membrane. Each molecule has:

• A hydrophilic (water-attracting) phosphate head

• Two hydrophobic (water-repelling) fatty acid tails

Due to this amphipathic nature, phosphoglycerides arrange themselves into a bilayer, forming the basic framework of the cell membrane as explained by the fluid mosaic model. In this bilayer:

• Hydrophilic heads face the aqueous environment (outside and inside the cell)

• Hydrophobic tails face inward, away from water

This structure provides:

• Selective permeability (controls movement of substances)

• Fluidity (allows proteins and lipids to move within the membrane)

• Structural integrity to the cell