When first laid down, these are fairly soft, flexible, and extensible. These walls elongate as the cells enlarge during the maturing of plant tissues. During and after cell elongation, additional cell wall materialis laid down on the surfaces facing plasma membrane, which produces the secondary cell walls on mature plant cells, which are much thicker and more rigid than their predecessors. The primary cell walls are simple structures which consist of a single layer of primarily homogenous wall material, while secondary walls are very complex, multilayered walls which occur in a near infinite amount of structural forms. In the plant cell walls, Most of the fiber and network molecules are polysaccharaides, built up from multiple combinations of a fairly short list of monosaccharide subunits.
Proteins are present either as structural elements or enzymes in wall synthesis.
Most of those structural proteins are glycoproteins. These subunits link in straight or branched chains in the plant cell wall molecules. The major fiber of higher plant cell walls is cellulose , which is formed completely from glucose subunits that are link together in unbranched, linear chains. These polysaccharides with this sort of linkage usually are very highly soluble. As many as 6000-7000 glucose units can be linked end to end in each cellulose molecule in primary cell walls.