Cerebrosides

CiaH3 7N02,CH3-[CH2],2-CH CH.CH(0H). CH(NH2>-CH20H. a base, forming part of the molecules of sphingomyelins and the cerebrosides, from which it splits off on hydrolysis. It crystallizes in needles from ether. 

Cerebrosides are found in the brain and in the myelin sheath of nerve tissue The structure of the cerebroside phrenosine is... 

FIGURE 8.13 The structure of a cerebroside. Note the sphiugosiue backbone. 

Component of the myelin sheath surrounding the axons of nerve cells. Additional compounds of the myelin sheath are phospholipids, cholesterol, cerebrosides, and specific keratins. The myelin sheath constitutes an isolating barrier during electrophysiological axonal signaling. 

The glycosphingolipids (GSLs) are sugar-containing lipids built on a backbone of ceramide they include galactosyl- and glucosylceramide (cerebrosides) and the gangliosides. Their structures are described in Chapter 14. They are mainly located in the plasma membranes of cells. 

Cerebrosides, snlfatides, gangliosides, and other glycolipids appear as yellow spots cholesterol appears as a light red spot... 

Sphingolipids (ceramids, sphingomyelin, cerebrosides, sulfatides, gangliosides) and lipids with secondary amines produce blue spots on a white backgound (CAUTION benzidine is a carcinogen)... 

Phosphatidyl Glycerol Phosphatidyl Inositol Cerebrosides Gangliosides... 

D-Galactose H HO HO H HOH2 C—C—C—C—C—CHO HO H H HO widespread in plants lactose ovomucoid cerebrosides albumin gland of snail frog and toad spawn beef lung... 

Because membranes components participate in nearly every cell activity their structures are also dynamic and far from the equilibrium states that are most readily understood in biophysical terms. Newly synthesized bilayer lipids are initially associated with endoplasmic reticulum (Ch.3) whereas phospholipids initially insert into the cytoplasmic leaflet while cholesterol and sphingolipids insert into the luminal endoplasmic reticulum (ER) leaflet. Glycosylation of ceramides occurs as they transit the Golgi compartments, forming cerebrosides and gangliosides in the luminal leaflet. Thus, unlike model systems, the leaflets of ER membranes are asymmetric by virtue of their mode of biosynthesis. 

Central nervous system myelin is enriched in certain lipids. Table 4-1 lists the composition of bovine, rat, and human myelin compared to bovine and human white matter, human gray matter, and rat whole brain [1] (see Ch. 3). While there are no absolutely myelin-specific lipids, cerebroside (galactosyl ceramide) is the most typical of myelin. With the exception of early development,... 

---