Stein Wilfred D
Department of Biological Chemistry, Silberman Institute of Life Sciences, Hebrew University, Jerusalem, Israel.
Int Rev Cytol. 2002;215:231-58. doi: 10.1016/s0074-7696(02)15011-x.
Plant cells and bacterial cells are surrounded by a massive polysaccharide 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, and can take on a variety of shapes and can change these from moment to moment. This osmotic balance is achieved, in the first place, by the action of the energy-consuming sodium pump, one of the P-type ATPase transport protein family, members of which are found also in bacteria. The pump's action brings about a transmembranal electrochemical gradient of sodium ions, harnessed in a range of transport systems which couple the dissipation of this gradient to establishing a gradient of the coupled substrate. These transport systems include many which are responsible for short-term regulation of the cell's volume in response to acute changes of their osmotic balance. Thus, the primary role of the sodium pump as a regulator of cell volume has been built upon to provide the basis for an enormous variety of physiological functions.
植物细胞和细菌细胞被一层厚实的多糖壁所包围，这限制了它们较高的内部渗透压（数十个大气压）。相比之下，动物细胞与其环境处于渗透平衡状态，没有限制其形态的外层结构，能够呈现出各种形状，并且可以随时改变这些形状。这种渗透平衡首先是通过耗能的钠泵来实现的，钠泵是P型ATPase转运蛋白家族的一员，细菌中也存在该家族的成员。钠泵的作用产生了钠离子的跨膜电化学梯度，该梯度被一系列运输系统所利用，这些运输系统将该梯度的消散与建立耦合底物的梯度相耦合。这些运输系统包括许多负责根据细胞渗透平衡的急性变化对细胞体积进行短期调节的系统。因此，钠泵作为细胞体积调节器的主要作用得到了进一步拓展，为多种多样的生理功能奠定了基础。
