Membrane phospholipids are a type of lipid that are major components of cell membranes. They are composed of a hydrophilic (water-loving) head group and a hydrophobic (water-repelling) tail, and their unique structure allows them to form a bilayer that makes up the main structural component of the cell membrane.

Phospholipids are amphipathic, meaning that they have both hydrophilic and hydrophobic regions. The hydrophilic head groups are typically composed of a glycerol molecule, which is linked to a phosphate group and a small polar molecule such as choline, serine, or ethanolamine. The hydrophobic tails are typically long hydrocarbon chains that can be saturated or unsaturated.

Phospholipids are distributed asymmetrically in the cell membrane, with different types of phospholipids concentrated in different regions. For example, phosphatidylcholine and sphingomyelin are found primarily in the outer leaflet of the membrane, while phosphatidylserine and phosphatidylethanolamine are primarily located in the inner leaflet.

Membrane phospholipids play a number of important roles in cell function. They help maintain the integrity of the cell membrane, regulate membrane fluidity, and serve as precursors for signaling molecules such as diacylglycerol and inositol triphosphate. Dysregulation of membrane phospholipid metabolism has been implicated in a number of diseases, including cancer, neurodegenerative disorders, and cardiovascular disease.