Structural Lipids in Membranes:- Sphingolipids at Cell Surfaces Are Sites of Biological Recognition

When sphingolipids were discovered a century ago by the physician-chemist Johann Thudichum, their biological role seemed as enigmatic as the Sphinx, for which he therefore named them. In humans, at least 60 different sphingolipids have been identified in cellular membranes. Many of these are especially prominent in the plasma membranes of neurons, and some are clearly recognition sites on the cell surface, but a specific function for only a few sphingolipids has been discovered thus far. The carbohydrate moieties of certain sphingolipids define the human blood groups and therefore determine the type of blood that individuals can safely receive in blood transfusions (Fig. 10–14).

FIGURE 10–13 The similarities in shape and in molecular structure of phosphatidylcholine (a glycerophospholipid) and sphingomyelin (a sphingolipid) are clear when their space-filling and structural formulas are drawn as here.

FIGURE 10–14 Glycosphingolipids as determinants of blood groups. The human blood groups (O, A, B) are determined in part by the oligosaccharide head groups (blue) of these glycosphingolipids. The same three oligosaccharides are also found attached to certain blood proteins of individuals of blood types O, A, and B, re spectively. (Fuc represents the sugar fucose.)

Gangliosides are concentrated in the outer surface of cells, where they present points of recognition for extracellular molecules or surfaces of neighboring cells. The kinds and amounts of gangliosides in the plasma membrane change dramatically during embryonic development. Tumor formation induces the synthesis of a new complement of gangliosides, and very low concentrations of a specific ganglioside have been found to in duce differentiation of cultured neuronal tumor cells. Investigation of the biological roles of diverse gangliosides remains fertile ground for future research.

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وجع الأوتار قد يخفي خطرا صحيا مرتبطا بالقلب

أزمة "السفينة الموبوءة"..الأرجنتين تحقق في مصدر تفشي "هانتا"

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مواضيع ذات صلة

Lipids as Signals, Cofactors, and Pigments: -Plants Use Phosphatidylinositols, Steroids, and Eicosanoidlike Compounds in Signaling

Lipids as Signals, Cofactors, and Pigments:- Steroid Hormones Carry Messages between Tissues

Lipids as Signals, Cofactors, and Pigments:- Phosphatidylinositols and Sphingosine Derivatives Act as Intracellular Signals

Structural Lipids in Membranes:- Sterols Have Four Fused Carbon Rings

Structural Lipids in Membranes:- Sphingolipids Are Derivatives of Sphingosine

Structural Lipids in Membranes:- Chloroplasts Contain Galactolipids and Sulfolipids

Structural Lipids in Membranes:- Some Phospholipids Have Ether-Linked Fatty Acids

Structural Lipids in Membranes:- Glycerophospholipids Are Derivatives of Phosphatidic Acid

Storage Lipids:- Many Foods Contain Triacylglycerols

Storage Lipids:- Triacylglycerols Provide Stored Energy and Insulation

Storage Lipids:- Triacylglycerols Are Fatty Acid Esters of Glycerol

Storage Lipids:- Triacylglycerols Are Fatty Acid Esters of Glycerol