Topic overview

Start with the big picture

Built from a phospholipid bilayer with integral and peripheral proteins, the cytoplasmic membrane forms a selectively permeable barrier in all bacteria. Most bacteria lack sterols, while Mycoplasma and Ureaplasma can incorporate host-derived sterols; hopanoids help stabilize fluidity in many species. The membrane hosts transport systems and supports electron transport, oxidative phosphorylation, and ATP synthesis through the proton motive force. It also contributes to cell-wall precursor assembly, chromosome segregation, septum formation, motility, and signaling. Distinguishing it from the Gram-negative outer membrane is important: porins are located in the outer membrane, not the cytoplasmic membrane. The lesson also addresses membrane disruption, drug efflux, antimicrobial targeting, and the misconception that mesosomes are true structures.