Question

Why do glycerophospholipids and sphingolipids—but not fatty acids—form bilayers?

Short answer

Lipids have a polar phosphate group and a non-polar tail. A polar head and a non-polar tail are necessary for the formation of a bilayer, whereas fatty acids only have the non-polar feature.

Step-by-step solution

Introduction

The lipid bilayer (also known as the phospholipid bilayer) is a two-layer polar membrane made up of lipid molecules. These membranes have a flat sheet-like arrangement and form a continuous barrier around all cells. The nuclear membrane encircling the cell nucleus, as well as the membranes of the membrane-bound organelles in the cell, are all formed of a lipid bilayer.

Glycerophospholipids and sphingolipids form bilayers

Micelles are made up of fatty acids (a circle of fatty acids with polar head groups protruding and a single hydrophobic chain). Glycerophospholipids and sphingolipidscannot form a micelle due to steric hindrance and instead form a bilayer.

Conclusion

Thus, the glycerophospholipids and sphingolipids cannot form the micelle due to the process of steric hindrance. This allows the lipid molecules to form a layered structure in the cell membrane. The micelle formation by the fatty acids does not allow it to be a part of the membrane layer.