toisiolähettimolekyyli

Toisiolähettimolekyyli, or secondary messenger molecule, is a signaling molecule within a cell that propagates the signal from a receptor to target molecules. When an external signal, such as a hormone or neurotransmitter, binds to a cell surface receptor, it initiates a cascade of intracellular events. This often involves the activation of enzymes that produce or release secondary messengers. These messengers, in contrast to primary messengers (the initial external signals), are not directly synthesized or released by the external stimulus itself but are generated or mobilized within the cell as a consequence of the primary signal.

Common examples of toisiolähettimolekyylit include cyclic adenosine monophosphate (cAMP), cyclic guanosine monophosphate (cGMP), inositol trisphosphate (IP3), and diacylglycerol (DAG). Calcium ions (Ca2+) also frequently act as secondary messengers. Each type of secondary messenger can interact with specific target proteins, such as kinases, phosphatases, or ion channels, leading to a variety of cellular responses. These responses can include changes in gene expression, metabolic activity, cell division, or muscle contraction. The amplification of the initial signal is a key feature of secondary messenger systems; a single activated receptor can lead to the production of many secondary messenger molecules, thus greatly amplifying the cellular response.