Stein W D
Silberman Institute of Life Sciences, Hebrew University, Jerusalem, Israel.
Philos Trans R Soc Lond B Biol Sci. 1995 Sep 29;349(1329):263-9. doi: 10.1098/rstb.1995.0112.
Plant cells and bacterial cells are surrounded by a massive cellulose wall, which constrains their high internal osmotic pressure (tens of atmospheres). Animal cells, in contrast, are in osmotic equilibrium with their environment, have no restraining surround, can take on a variety of shapes and change these from moment to moment. This osmotic balance is achieved by the action of the energy-consuming sodium pump, one of the P-type ATPase transport protein family, members of which are indeed also found in bacteria. The pump's action brings about a transmembranal electrochemical gradient of sodium ions, harnessed in a range of transport systems that couple the dissipation of this gradient to establishing a gradient of the coupled substrate. The primary role of the sodium pump as a regulator of cell volume has evolved to provide the basis for an enormous variety of physiological functions.
植物细胞和细菌细胞被一层厚厚的纤维素壁包围着，这限制了它们较高的内部渗透压（几十大气压）。相比之下，动物细胞与其环境处于渗透平衡状态，没有限制它们的外层结构，可以呈现各种形状并随时改变这些形状。这种渗透平衡是通过耗能的钠泵实现的，钠泵是P型ATPase转运蛋白家族的一员，实际上在细菌中也能找到该家族的成员。钠泵的作用产生了钠离子的跨膜电化学梯度，该梯度被一系列转运系统利用，这些系统将这种梯度的消散与建立偶联底物的梯度联系起来。钠泵作为细胞体积调节器的主要作用已经演变为各种生理功能的基础。
