Receptoru

Receptoru, the term used in Romanian for “the receptor,” refers to a biomolecule that binds a specific ligand and translates chemical signals into a cellular response. Receptors are typically proteins or glycoproteins located on the cell surface or inside the cell and detect signals such as hormones, neurotransmitters, cytokines, nutrients, and drugs. Binding depends on affinity and specificity, and receptors can become saturated at high ligand concentrations. Receptors may be upregulated or downregulated in response to stimuli, altering cell sensitivity.

Receptors are commonly categorized by location and mechanism. Cell-surface receptors include ligand-gated ion channels, G protein-coupled receptors (GPCRs), and enzyme-linked receptors such as receptor tyrosine kinases. Intracellular receptors reside in the cytoplasm or nucleus and typically regulate gene expression after ligand binding, as with steroid or thyroid hormone receptors.

Ligand binding initiates signaling cascades that alter cellular activity. Outcomes may include opening or closing ion channels, activating enzymes, triggering second messengers (cAMP, Ca2+), or changing transcription of target genes.

Receptors display pharmacological properties such as agonism, antagonism, partial agonism, and inverse agonism. Regulation of receptor number and responsiveness includes desensitization, internalization, recycling, or degradation, shaping responses to ongoing signals. Receptors are central to physiology and pharmacology, underpinning neural communication, metabolic control, immunological responses, and sensory perception. They are also major targets for therapeutic drugs, making understanding their function important in medicine and biotechnology.