This multi-volume set within International Review of Cytology encompasses the recent advances in the understanding of structure-function relationships at the molecular level of receptors, transporters, and membrane proteins. Several diverse families of membrane receptors/proteins are discussed with respect to the molecular and cellular biology of their synthesis, assembly, turnover, and function. Included are such receptor superfamilies as G-proteins, immunoglobulins, ligand-gated receptors, interleukins, and tyrosine kinases as well as such transporter/protein families as pumps, ion channels, and bacterial transporters. Each section of each volume features a "perspectives/commentary" chapter which includes comments on the recent advances and predictions on new directions. Written by acknowledged experts in the field, this volume, 137C, highlights recent developments in pumps, channels, and transporters.