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据估计人体结构中约有75万亿(trillion,1×10~(18))个细胞,它是人体的基本结构单位,人体内所有的生理机能和生化反应都是在细胞及其产物(如细胞间隙中的胶元和蛋白聚糖等)的物质基础上进行的。细胞膜是细胞质的一个特殊组成部分,它把细胞内容物和细胞的外部环境分开,使细胞能够独立存在。细胞膜还能保持细胞内容物不致流失。同时细胞本身在新陈代谢过胞程中所需的营养物质和代谢产物,又必须通过细胞膜与周围环境进行物质交换,使得细内化学成分保持相对恒定。细胞膜具有选择性通透和主动转运的特性,以维持细胞内
It is estimated that there are about 75 trillion (1 × 10 ~ 18) cells in human body structure. It is the basic structural unit of the human body. All the physiological functions and biochemical reactions in the human body are in the cells and their products Cell gap in the gum yuan and proteoglycans, etc.) on the basis of the material. The cell membrane is a special part of the cytoplasm that separates the contents of the cell from the external environment of the cell so that the cell can exist independently. Cell membrane can also keep the contents of the cell will not be lost. At the same time the cells themselves in the metabolic process required nutrients and metabolites, but also through the cell membrane and the surrounding environment for material exchange, making the fine chemical composition remained relatively constant. Cell membrane has the characteristics of selective permeability and active transport to maintain intracellular