Gastrointestinal absorption pathway

Gastrointestinal absorption pathways refer to the diverse molecular mechanisms by which nutrients, water, and drugs cross the intestinal epithelium and enter the bloodstream or lymphatic system. Major routes include passive diffusion (for small, lipophilic molecules), active transport (carrier-mediated, requiring energy and often substrate specificity), facilitated diffusion (via specific membrane proteins), and paracellular flow (movement between cells via tight junctions, important for small ions and hydrophilic drugs). Key molecular components include transporters such as SGLT1 (sodium-glucose cotransporter), GLUT5 (fructose transporter), PepT1 (peptide transporter), P-glycoprotein (drug efflux transporter), along with enzymes like CYP3A4 for metabolism and tight junction proteins responsible for barrier function. The efficiency and capacity of gastrointestinal absorption directly affect nutrient status, pharmacokinetics for oral drugs, and risk for malabsorption diseases or adverse drug reactions. “Gastrointestinal absorption pathways” describes a process encompassing many distinct molecular targets (e.g., SGLT1, GLUT2, PepT1, P-glycoprotein, claudins, CYP3A4) rather than a single target molecule. If further detail is needed for a specific transporter, enzyme, or protein within these pathways, please specify the molecular name (e.g., “P-glycoprotein,” “SGLT1,” “PepT1,” etc.).

Other names

GI absorption pathwayintestinal absorption mechanismsnutrient absorption routes

Passive diffusion (across lipid bilayer), Active transport (carrier protein-mediated), Facilitated diffusion (specific transmembrane proteins), Endocytosis (occasionally for large molecules)