retseptorile
Retseptorile (receptors) are cellular proteins that bind ligands such as hormones, neurotransmitters, drugs, or sensory stimuli, allowing cells to perceive and respond to external and internal signals. They are located on the cell surface or inside the cell, and they translate chemical binding into a cellular response through signaling pathways or changes in gene expression.
There are several major classes: membrane receptors, including G protein–coupled receptors (GPCRs), receptor tyrosine kinases, and
Binding of a ligand to a receptor is often highly specific, and the strength of binding (affinity)
Receptor regulation includes desensitization, internalization, and up- or down-regulation in response to prolonged exposure to ligands.