ABSTRACT
In contrast to unicellular organisms, in multicellular organisms cells interact with one another through cell-cell physical chemical ( paracrine o r h ormonal) co ntacts. e ph ysical c ell-cell interactions occur t hrough cell junctions w ith binding of proteins p resent w ithin t he memb ranes o f e ach c ell. F or d istant interactions, molecules secreted (ligands) are recognized by speci c receptors on the target cell membrane or in the target cell, depending on the hydrophobicity of the ligand.
