Amongst calcifying unicellular algae, coccolithophores have a high CaCO₃ production rate. The 5mm species Emiliania huxleyi mineralizes calcite liths equal to approximately 25% of their cell mass daily. As lith calcification occurs in a golgi derived vesicle this results in significant intracellular H⁺ generation. The large CaCO₃ liths are exocytosed to the cell surface at a rate of approximately 1 hr^-1, instigating a high degree of membrane cycling. The cellular mechanisms behind the maintenance of acid-base homeostasis and regulation of membrane cycling remain unknown in calcifying coccolithophores to date. Our fluorimetric measurements with E. huxleyi have revealed a weak acid-base regulatory ability in the cell, that can be specifically attributed to a high proton permeability. We interpret these results as a proton removal pathway for H⁺ produced during calcification. Ongoing experimental work is focused on determining the structure of the membrane system enclosing the cell. In contrast to existing literature, we conclude from TEM images that E. huxleyi has a cell cover between the liths and plasma membrane. Unlike traditional algal and plant cell walls, the cell cover of calcifying E. huxleyi does not stain positive for ß-glucan carbohydrates with Calcofluor. However, positive staining with the lipophilic styryl dye FM1-43 is evident as two concentric structures when cytoplasmic volume is reduced during exposure of the cells to hyperosmotic conditions. Further efforts to characterise the composition of the cell cover include enzymatic digestion experiments with lyases targeting various structural molecules and higher resolution electron microscopy. Understanding of the peripheral membrane system is necessary for the advancement of knowledge on calcification relevant regulation of membrane cycling in coccolithophorid cells.