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3.2.2.2.1. Phospholipids

Phospholipids

The phospholipids are a class of compounds by a lipid molecule Alcohol (glycerol or sphingosine), which bind two fatty acids and a phosphate group. Phosphate is linked by a phosphodiester bond to another group of atoms, which generally contain nitrogen, such as choline, serine or ethanolamine and often have an electrical charge.

Phospholipids have an amphipathic behavior, since they present:

  • polarhydrophilic zone, formed by the phosphate group attached to an alcohol,
  • an apolarlipophilic zone in which two fatty acids appear.

Fosfolípido

By No machine-readable author provided. Lennert B assumed (based on copyright claims). [Public domain], via Wikimedia Commons

This amphipathic behavior allows them to form lipid bilayers, the main component of the plasma membrane, where the apolar tails of both layers face each other, while the polar heads are oriented towards the external and internal environment, both aqueous.

Fosfolipido

By Rupertsciamenna. Versión en español de Alejandro Porto. (File:Fosfolipide.svg) [CC BY-SA 3.0], via Wikimedia Commons

Bicapa lipídica

By Bensaccount [Public domain], via Wikimedia Commons

The phospholipids are divided into:

Phosphoglycerides

The phosphoglycerides (phosphatidic acid derivatives) are triesters of glycerol,

The most abundant phosphoglycerides include: phosphatidylserine, the lecithin or phosphatidylcholine and cephalin or phosphatidylethanolamine, molecules especially abundant in the membranes of eukaryotic cells.

Fosfoglicéridos

By miguelferig (Own work) [CC0], via Wikimedia Commons

Animated image: Formation of a phosphoaminolipid .

Sphingolipids

The fosfoesfingolípidos are esters formed by:

  • Ceramide, formed by the union through an amide bond, of:
    • Sphingosine, an 18-carbon unsaturated amino alcohol.
    • A long chain fatty acid.
  • phosphoric acid.
  • An amino alcohol.

The most abundant phosphoesphingolipid is sphingomyelin, a constituent of the myelin sheaths that surround the axons of neurons.

    Formación de un esfingolípido
    animaesfingo.gif (Imagen GIF, 600 × 400 píxeles) - Escalado (0 %). (s. f.). Recuperado a partir de http://recursos.cnice.mec.es/biosfera/alumno/2bachillerato/biomol/imagenes/lipido/animaesfingo.gif

    Fundamental Ideas About Phospholipids

    • Characteristics of phospholipids.
      • They are a type of saponifiable lipids, they contain fatty acids.
      • The phospholipids are composed of a molecule  Alcohol (glycerol or sphingosine), which bind two fatty acids  and a phosphate group.
      • Like fatty acids, they exhibit amphipathic behavior that allows them to form lipid bilayers. They are made up of:
        • polarhydrophilic zone, formed by the phosphate group attached to an alcohol  
        • an apolarlipophilic zone in which two fatty acids appear.    
    • Classification of phospholipids:
      • Phosphoglycerides: (alcohol is glycerol, a short chain alcohol).
      • Sphoingolipids: (alcohol is  sphingosine , a long-chain alcohol).
        • Ceramide , formed by the union through an amide bond,of:   
          • Sphingosine , an 18-carbon unsaturated amino alcohol.
          • A long chain fatty acid .  
        • phosphoric acid
        • An amino alcohol