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The channel has a large diameter of 0.8x1.1nm, and is non-selective for small ions. However, it has an upper exclusion size limit corresponding to molecular weights of about 600 Dalton of permeants. Because most metabolites have molecular weights lower than 600 Da and have been shown to pass through porin channels, porins are called general diffusion pores.
Ion Channels. Photo by: stef. Ions are charged particles such as Na + , H + , K + , Ca 2+ , and Cl - . Ions have a significant effect on many cell processes and also influence the amount of water in the cell. Cells use inorganic ions for transmitting signals across the cell membrane or along the surface of the cell.