Bacterial cell wall polysaccharide structure

Bacterial Cell Wall Polysaccharides (Figure 9,25, Figure 9.26, Structure) Glycoproteins (Table 9,6)... 

What role do polysaccharides play in the structure of cell walls In bacterial cell walls, polysaccharides are cross-linked to peptides. Plant cell walls consist primarily of glucose. 

As mentioned, lysozyme hydrolyzes glycosidic linkages in the peptidoglycan polymer of gram-positive bacterial cell walls. The structure of an oligosaccharide similar to the polysaccharide found in bacterial cell walls is shown in Fig. 24.16. //-Acetylglucosamine (NAG) and //-acetylmuramic acid (NAM) form alternating repeat units in this polysaccharide. 

Chitin is a polysaccharide that has a structure very similar to that of cellulose and the bacterial cell wall polysaccharide murein. The structure of chitin is essentially the structure of cellulose, with the hydroxyl group at C-2 of the D-glucopyranose residue substituted with an A -acetylamino group [132] (see Fig. 6.15A). Chitin is the structural polysaccharide that replaces cellulose in the cell wall of many species of lower plants. It is found in fungi, yeast, green algae, and brown and red seaweed cell walls. Chitin is also the major component of the exoskeleton of insects. It is found in the cuticles of annelids, molluscs, and in the shells of crustaceans such as shrimp, crab, and lobster [133]. 

The presence and biological importance of oligosaccharide structures, usually as components of glycolipids and glycoproteins, in bacterial capsular and cell-wall polysaccharides, in mammalian cell membranes, in cytoplasm, and in extracellular fluids, are now well documented. They are important constituents in... 

This article, which is the fourth in the current series,1 presents a bibliographic account of the crystal structures of polysaccharides that have been published during 1977-1979. Several comprehensive reviews on the structures of glycosaminoglycans,2-5 bacterial capsular polysaccharides,3 4,6 starch,7-9 and cell-wall polysaccharides,10 and on... 

The complex structure of bacterial cell walls is discussed in Chapter 8. However, it is appropriate to mention a few bacterial polysaccharides here. The innermost layer of bacterial cell walls is a porous network of a highly crosslinked material known as pepti-doglycan or murein (see Fig. 8-29). The backbone of the peptidoglycan is a P-l,4-linked... 

Polysaccharides are the major structural component of all cell walls. We focus on bacterial cell walls because their synthesis is the best understood, and understanding their synthesis has clarified the role of numerous antibiotics. 

Particularly it became necessary to consider the bacterial membrane. As things stand now, the bacterial cell wall is thought of as an outer skeleton which can be freely traversed by macromolecules and is important for the mechanical structure and protection of the cell. It is made up of polysaccharides and carbohydrate-derived substances, which include some peptide groups. Underneath the cell wall there is the cell membrane, which appears to be the seat of the important physiological functions of assimilation and excretion. Some findings suggest... 

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