CELL MEMBRANE GLYCOLIPIDS скачать в хорошем качестве

CELL MEMBRANE GLYCOLIPIDS

Among membrane lipids, it is the sphingophospholipids, not glycerophospholipids, that give rise to glycolipids. Glycerophospholipids are built on a small, flexible three-carbon alcohol, glycerol, which readily interacts with various alcohol-containing head groups. In contrast, sphingosine is a robust 18-carbon amino alcohol, and it dares to do something special: it carries carbohydrates. The backbone of all glycosphingolipids is ceramide, which is formed when a long-chain fatty acid attaches to sphingosine via its amino group. Once ceramide is formed, mono- or oligosaccharides attach to sphingosine, giving rise to different classes of glycosphingolipids. If a single monosaccharide is attached, the molecule is called a cerebroside. If the sugar is glucose, it forms a glucocerebroside. If the sugar is galactose, it forms a galactocerebroside. When a disaccharide is attached, the result is a globoside, with lactosylceramide being a classic example. Now comes the complexity. The entry of N-acetylneuraminic acid (NANA, or sialic acid) converts the molecule into a ganglioside.With NANA alone, it is GM₃ Addition of N-acetylgalactosamine forms GM₂ Addition of another galactose produces GM₁ And this is how the carbohydrate crown of glycosphingolipids is directed outward into the extracellular space, where it participates in cell recognition and signaling. From a chemical perspective: Glucose or galactose produces neutral glycosphingolipids Sulfate groups or NANA generate acidic glycosphingolipids Together, these surface carbohydrates form the glycocalyx,the sugar coat of the cell membrane.Clinical and applied biochemistry for Medical Students and DoctorsBiochemical basis for clinical manifestations of metabolic disorders