Cell adhesion provides organized tissue structure and allows the transmission of molecular signals for cell-cell communication. In plants, most cell-cell adhesions are mediated by cell wall polysaccharides, such as pectins. During cell division, as a plate forms between the dividing cells, RG II, a pectin polysaccharide, localizes at the plate and helps early-stage adhesion. As the cells mature, pectins are distributed across the primary cell wall and middle lamella. Pectins have a negatively charged galactouran backbone that gets cross-linked by calcium ions. The resulting polysaccharide network connects adjacent cells, maintaining tissue integrity. Though plant cells adhere closely, the thick cell walls prevent the free diffusion of molecules. Structures called plasmodesmata, functionally similar to gap junctions in animal cells, form continuous channels connecting the cytosol of adjacent cells. Such channels allow molecules to pass through, aiding cell-cell communication.