Job done by cell surface membrane

I once read a poem that said"The sky like a lid cover the earth, the contiment like a chess board, human like a chess". Human body was composed of various kinds of cells, which was the minimal functional units. Millions of cells work together and suport the integral works of human being. Though there are many types of cells, like neuron, epithelial, fibroblast cells, one components was common in all cells. It is called cell surface membrane.

Cell membrane was a common structure of all of organisms, from microorganims like virus, bacterial, yeast to vertebrate animals. Cell surface membranes was a barrier, which sperates intracellular space from extracellular spaces. K+ was high permeable in membranes, but the proteins which was completely inhibited to enter or exit the membrane freely.

Functions of cell surface membranes was various. First, it maintain the physical shape of cell by interacting with cellular skeleton. Second, it was a physical barrier that distinguish the intracellular space with extracellular space and maintain the hemeostasis of cells. It also regulate the composition of cellular components and transmembrane transport. Cells communicate with other cells and induce appropriate response. It also can transmit extracellular signals into cells and transduce electric signal to neighboing cells. Another important function was to release intracellular materials to extracellular space.