Definition

Noun: A phospholipid is a type of lipid (fat) molecule that is a fundamental structural component of all cell membranes. It is characterized by having a hydrophilic (water-attracting) "head" containing a phosphate group and a nitrogenous base, and two hydrophobic (water-repelling) "tails" composed of fatty acids.

Usage

Phospholipids spontaneously arrange themselves into a double layer (bilayer) in aqueous environments, forming the basic structure of biological membranes. This bilayer creates a barrier that separates the inside of a cell from its external environment.

Examples

• The cell membrane is primarily composed of a phospholipid bilayer.
• Phospholipids are amphipathic molecules, meaning they have both water-soluble and water-insoluble parts.
• Lecithin, a common food additive, is a type of phospholipid.

Advanced Usage

• Phospholipid asymmetry: Refers to the difference in phospholipid composition between the inner and outer leaflets of the cell membrane, which is crucial for cell function and signaling.
• Phospholipid scramblase: An enzyme that disrupts this asymmetry, allowing phospholipids to move between the two layers of the membrane.

Variants and Related Words

• Phospholipid bilayer (noun phrase): The double layer of phospholipids that forms the core structure of cell membranes.
• Phospholipase (noun): An enzyme that catalyzes the hydrolysis of phospholipids.

Synonyms

• Membrane lipid
• Polar lipid (in a broad biochemical context)

Different Meanings

The term phospholipid is specific to biochemistry and cell biology. It does not have common alternative meanings in everyday language.

Related Phrases/Concepts

• Fluid mosaic model: The scientific model that describes the cell membrane structure, in which phospholipids provide the fluid bilayer.
• Amphipathic/Amphiphilic: The key property of phospholipids, having both hydrophilic and hydrophobic regions.

Noun

1. any of various compounds composed of fatty acids and phosphoric acid and a nitrogenous base; an important constituent of membranes