Which type of signaling involves molecules acting on nearby cells?

Paracrine signaling involves molecules that act on nearby cells, facilitating local communication between cells in close proximity. In this form of signaling, the cells release signaling molecules into the surrounding extracellular space, which then bind to receptors on neighboring cells, thereby influencing their behavior or function.

In contrast, endocrine signaling involves hormones that are released into the bloodstream and can affect distant target cells throughout the body. Juxtacrine signaling requires direct contact between the signaling cell and the target cell, usually via membrane-bound molecules, without the need for diffusion. Exocrine signaling refers to substances being secreted outside the body or into a body cavity (like sweat or digestive enzymes) rather than influencing nearby cells.

Given this context, paracrine signaling is distinct because it specifically highlights the action of signaling molecules on nearby cells, effectively allowing for localized and high-speed communication. This mechanism is crucial in many biological processes, such as immune responses and tissue development.