# Cell Signaling --- **Cell signaling**, or **cell-cell communication** is a very complex and vitally important aspect of how [[biology|organisms]] function. Cell signaling describes how specific information can be transferred from one cell to the next, even from opposite sides of the organism. There are four broad categories that signaling call fall under: - **[[cell junction|direct contact]] signaling** - **[[synapse|synaptic]] signaling** - **[[endocrine system|endocrine]] signaling** - **autocrine signaling** - **paracrine signaling** ## Signaling Between Unicellular Organisms [[unicellular cell signaling]] ## Signaling in Multicellular Organisms A multicellular organism is made up of many cells that all have the same genetic information. **Cell communication allows all those cells to *coordinate* and determines so much of what the cell does**. For example, what genes it expresses, when to grow, when to stop growing, how to build it's extracellular environment, when to divide, when to replace themselves, or when to recruit help from other body systems (such as the immune system). ### Communication Between Adjacent Cells Sometimes neighboring cells can have incredibly different functions, yet they remain in constant communication (such as the cells that line the stomach). Adjacent cells in multicellular organisms are often [[cell junction|attached]] to each over directly, or multiple cells can be attached to the same part of the [[extracellular matrix|ECM]]. These connections are called "[[cell junction|cell junctions]]", and they help cells stay in *constant communication*, allowing them to share resources, like ATP, or amino acids. They also allow cells to move around and remain pliable. ### Communication Between Distant Cells [[molecular signaling|Signaling]] to distant cells is a little more involved. [[signaling molecule|Signaling molecules]] such as hormones are released into the system and activate a specific [[receptor proteins]], which responds by making a change withen the cell. ___