payment page
Direct Contact
The simplest form of cell-to-cell communication occurs when adjacent cells are in direct contact with one another. When either the cell membranes or cell walls are touching, cells can directly pass ions, small molecules, and metabolites to other cells. In animal cells, this exchange occurs through gap junctions. Gap junctions are protein channels that pass through both cell membranes and connect the cytoplasm of adjacent cells. In plant cells, this exchange happens through plasmodesmata. Plasmodesmata are protein channels that pass through the cell walls in addition to the cell membranes.
Chemical Signaling
Short distance communication, or paracrine signaling, occurs when local regulators or ligands are released by a cell that target cells nearby the signal-emitting cell. These signaling molecules spread into the extracellular space and then bind to receptors in the membranes of target cells.
Self-communication, or autocrine signaling, occurs in the same way as paracrine signaling but the messenger molecules bind to receptors on the same cell. This is often found in immune cells as a way of amplifying the immune response.
Long distance communication, or endocrine signaling, occurs when signals, often hormone molecules, released by a cell travel further to target cells of another cell type. The signaling cell and the target cell are often in different parts of the body and the signaling molecules travel through the bloodstream.
In the next section, we will explain what happens once these signals are received by the target cell.
