signaalinvälitysreaktion

Signaalinvälitysreaktio, known in English as signal transduction, is the process by which a cell responds to a stimulus. This stimulus, or signal, can originate from outside the cell, such as a hormone or neurotransmitter, or from within the cell itself. The signal binds to a receptor protein on the cell surface or within the cytoplasm, initiating a cascade of molecular events inside the cell.

This cascade typically involves a series of protein modifications, such as phosphorylation or dephosphorylation, and the activation of second messengers. These second messengers are small molecules that amplify the initial signal and relay it through the cell. The ultimate outcome of the signal transduction pathway is a specific cellular response. This response can vary widely, including changes in gene expression, enzyme activity, cell growth, differentiation, or even cell death.

Signal transduction is crucial for virtually all cellular processes and allows cells to communicate with each other and with their environment. It plays vital roles in development, immunity, metabolism, and neurological function. Dysregulation of signal transduction pathways is implicated in numerous diseases, including cancer, diabetes, and autoimmune disorders, making the study of these pathways a key area of biological research. Understanding how signals are transmitted and interpreted by cells is fundamental to understanding life at the molecular level.