Figure 1.

Cellular signaling controls various aspects of multicellular life forms. Not only the key biological processes such as cell division, differentiation, growth, and cell-cycle transition, but also specialized cell-specific functions such as neurotransmission, pathogen-sensing, phagocytosis, and antigen-presentation are controlled by specific signaling pathways. The process of autophagy and nutrient cycling and recycling are some accessory pathways that are triggered by definitive signaling cues.