除了病毒等少数生物,一切有机体均由细胞构成。细胞是生物体生命活动的基本单位。病毒不具有细胞结构,没有独立的代谢与能量转化系统,必须利用宿主细胞的各种条件进行增殖,因此,病毒是专性寄生的非细胞形态生命体。所以,对于病毒而言,细胞也是它生命活动的基本单位。细胞有原核细胞和真核细胞两大类。 In addition to a small number of viruses and other organisms, all organisms are composed of cells. Cell is the basic unit of biological life activity. Viruses have no cell structure and no independent metabolic and energy conversion systems. They must proliferate under various conditions of the host cell. Therefore, the virus is an obligate parasitic non-cell-shaped organism. So, for the virus, the cell is also the basic unit of its life activity. Cells have two types of prokaryotes and eukaryotes.