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[Biochemistry](https://durgical.com/en/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](https://pubchem.ncbi.nlm.nih.gov/compound/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

- [Prostaglandin and thromboxane synthesis](https://durgical.com/en/biochemistry/pathways/prostaglandin-and-thromboxane-synthesis/)

## Related conditions

- [Acute respiratory distress syndrome (ARDS)](https://durgical.com/en/conditions/acute-respiratory-distress-syndrome/)

## Related

- [Phospholipids](https://durgical.com/en/biochemistry/topics/phospholipids/)
- [Sphingomyelin](https://durgical.com/en/biochemistry/molecules/sphingomyelin/)
- [Membrane structure](https://durgical.com/en/biochemistry/topics/membrane-structure/)
- [LCAT (lecithin–cholesterol acyltransferase)](https://durgical.com/en/biochemistry/enzymes/lcat/)
- [Palmitate (palmitic acid)](https://durgical.com/en/biochemistry/molecules/palmitate/)

## 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.

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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)](https://pubchem.ncbi.nlm.nih.gov/compound/5497103) (PubChem, NCBI, 2026) · Public domain; [RCSB PDB - POV Ligand Summary Page](https://www.rcsb.org/ligand/POV) (RCSB Protein Data Bank, 2026); [Synthesis of PC](https://reactome.org/PathwayBrowser/#/R-HSA-1483191) (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.

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Source: https://durgical.com/en/biochemistry/molecules/phosphatidylcholine/
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