Molecules with a hydrophilic head and two hydrophobic tails that form cell membranes.
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Phospholipids are amphipathic molecules built from a glycerol backbone, two fatty acid tails and a phosphate group carrying a polar head such as choline or serine. The hydrophilic head interacts with water while the hydrophobic tails avoid it, so phospholipids spontaneously self-assemble into bilayers in water. These bilayers form the basic structure of cell membranes, enclosing the cytoplasm and organelles while acting as a barrier to most polar and charged substances. Membrane fluidity depends on the length and saturation of the tails, and cholesterol modulates it further. Phospholipids also give rise to signalling molecules, such as inositol trisphosphate and diacylglycerol.
Key ideas: Glycerol with two fatty acid tails and a phosphate head group (often with choline, as in phosphatidylcholine). They are amphipathic: heads in water, tails away, spontaneously forming bilayers about 5 nm thick, micelles or liposomes. The bilayer is a fluid mosaic, and unsaturated tails keep it fluid at body temperature.
Common mistakes and connections: Mistake: thinking membranes are held by covalent bonds between lipids; they are assembled by hydrophobic effect and are fluid. Phospholipids have two tails, not three like triglycerides. Links to soap micelles, cholesterol modulating fluidity and drug delivery liposomes.
A phospholipid bilayer is a selective barrier: water crosses readily while ions and polar molecules cannot, which is the basis of osmosis across cell membranes. The interactive lesson shows this as a live animation or chart.
Lecithin, or phosphatidylcholine, is a common phospholipid found in egg yolk and soybeans.
Molecules with a hydrophilic head and two hydrophobic tails that form cell membranes.
Phospholipids is a advanced topic in Biochemistry, Environment & Industry. It builds on beginner and intermediate topics, so review those first if needed.
Study these earlier topics in Biochemistry, Environment & Industry first: Fats and Oils, Saturated and Unsaturated Fatty Acids, Trans Fats.
The next topics in Biochemistry, Environment & Industry are Cholesterol and DNA Structure.
Yes. The interactive lesson includes a self-check question on Phospholipids, and the Biochemistry, Environment & Industry quiz draws on every topic in this area.
Phospholipids is topic 21 of 127 in Biochemistry, Environment & Industry.
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