Transmembrane Transporters

The transmembrane transport of drugs can be divided into passive transport and active transport: (1) Passive transport of small molecular substances from high concentration to low concentration is the simplest transmembrane transport method, which is a diffusion transport of drug molecules. Therefore, it is transported in a concentration gradient, does not consume energy, and has no saturation except for facilitating transport, and has no competitive inhibition. Passive transportation is divided into two ways: 1.1 Free diffusion: no need for carrier protein assistance, such as: oxygen, carbon dioxide, fat. 1.2 Assist in diffusion: need carrier protein assistance, such as: amino acids, nucleotides. Special case: Glucose enters and exits red blood cells. (2) Active transport requires trans-membrane transport of carrier and energy, so it does not depend on the concentration difference on both sides of the membrane, has saturation, and there is competitive inhibition. Small molecules are transported from low concentrations to high concentrations, such as mineral ions, and glucose enters and leaves cells other than red blood cells, requiring energy and carrier proteins.