Influence of permeant acids and bases on net potassium uptake byChlorella

✍ Scribed by H. W. Tromballa

• Publisher: Springer-Verlag
• Year: 1978
• Tongue: English
• Weight: 555 KB
• Volume: 138
• Category: Article
• ISSN: 0032-0935
• DOI: 10.1007/bf00386818

✦ Synopsis

Salts of membrane-permeant acids and bases strongly influence net K uptake by ChIorella fusca. Na phenylacetate, acetate, isobutyrate, propionate, and butyrate added to buffered algal suspensions containing 0.1~.2mM KC1 increasingly stimulated net K uptake. In contrast, K release was induced by the chlorides of imidazole, ammonia and methylamine. All these effects were found in the light and, less pronounced, in the dark. The dependence of the net K movements on the concentrations of the salts added and on the pH of the medium suggests that the free acids or bases are the effective agents. Between net uptake of K and uptake of labeled propionate a molar ratio close to 1 was found. It is concluded that the internal pH of the cell is changed by the permeants. Acidification of the cytoplasm stimulates extrusion of protons coupled to uptake of K. Alcalization brings about proton uptake and K extrusion. Apparently K/H exchange serves as a pHstar of the cell.