Resepter

Resepter, or receptors, are proteins that detect and respond to chemical signals. They bind specific ligands such as hormones, neurotransmitters, drugs, or environmental molecules, translating external cues into cellular responses.

They can be located on the cell surface (plasma membrane receptors) or inside the cell (intracellular receptors). Major classes include ligand-gated ion channels, G protein-coupled receptors, receptor tyrosine kinases and other enzyme-linked receptors, and intracellular receptors that regulate gene transcription.

Upon ligand binding, receptors initiate signaling cascades that convert a chemical signal into a cellular response. This can involve opening ion channels, activating enzymes via G proteins, triggering kinase pathways, or modulating gene expression through transcription factors.

Receptors show specificity and affinity for their ligands and can be upregulated or downregulated. They may become desensitized after prolonged stimulation, internalized by endocytosis, or degraded and replaced.

Clinically, many drugs target receptors, using agonists to stimulate or antagonists to block their activity. Examples include beta-adrenergic blockers, antihistamines, and opioid receptor ligands. The study of receptors integrates biochemistry, pharmacology, and physiology.