Biochemistry · Molecule
Phosphatidylcholine (lecithin) !
Phosphatidylcholine, or lecithin, is the most abundant membrane phospholipid and the basis of the surfactant that keeps alveoli open.
Updated 2026-11-01
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Key facts
- Glycerol + two fatty acids + phosphate + choline.
- Made by the Kennedy pathway (CDP-choline + diacylglycerol) or, in the liver, by methylating phosphatidylethanolamine with SAM.
- Dipalmitoyl phosphatidylcholine is the main lipid of lung surfactant (type II pneumocytes).
- LCAT takes the C2 fatty acid of lecithin to esterify cholesterol in HDL.
- Also called
- Lecithin, POPC (3D model)
- Formula
- C₄₂H₈₂NO₈P
- PubChem
- CID 5497103
Structure
- The 3D model (PDB POV) is POPC: palmitate at C1, oleate (cis) at C2 and phosphocholine at C3.
- The choline head is positive and the phosphate negative: a neutral zwitterion at physiological pH.
Clinical notes
- In preterm babies, lack of surfactant causes neonatal respiratory distress syndrome; antenatal corticosteroids speed up its production.
- Bile lecithin helps keep cholesterol in solution; when it falls short, cholesterol stones form.
Pathways
Related conditions
Related
- Phospholipids
- Sphingomyelin
- Membrane structure
- LCAT (lecithin–cholesterol acyltransferase)
- Palmitate (palmitic acid)
Test yourself
Think of the answer, then tap the question to see it.
Which phosphatidylcholine dominates lung surfactant?
Dipalmitoyl phosphatidylcholine, whose two saturated palmitates pack tightly at the air–water interface.
Which plasma enzyme uses lecithin to esterify cholesterol?
LCAT, which moves the C2 fatty acid of lecithin onto HDL cholesterol.
What are the parts of a lecithin?
Glycerol, two fatty acids, a phosphate and choline.
Molecules are shown in their neutral form, as the databases deposit them; in the cell the acids and phosphates are ionised.
Educational information, not medical advice. For any symptom, see a health professional.
Sources: 1-Palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (CID 5497103) (PubChem, NCBI, 2026) · Public domain; RCSB PDB - POV Ligand Summary Page (RCSB Protein Data Bank, 2026); Synthesis of PC (Reactome, 2026); Textbook of Biochemistry for Medical Students, 6th ed. (Jaypee Brothers Medical Publishers (Vasudevan DM, Sreekumari S, Vaidyanathan K), 2011).
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Representative model, for educational purposes only.