生命的结构基础.pptVIP

* Figure: 03-20a-b Title: A dual-natured molecule. Caption: a. Phospholipids are comprised of two long fatty acid tails attached to a head containing both a phosphate group (with a negative charge) and a nitrogen-containing group (with a positive charge). b. Since the head is polarized, it can bond with water and thus will remain submerged in it; the tails, on the other hand, have no such bonding capability. * Caption: a. An aqueous solution divided by a semipermeable membrane has a solute - in this case, salt - poured into its right chamber. b. As a result, though water continues to flow in both directions through the membrane, there is a net movement of water toward the side with the greater concentration of solutes in it. c. Why does this occur? Water molecules that are bonded to the sodium (Na+) and chloride (Cl-) ions that make up salt are not free to pass through the membrane to the left chamber of the container. 渗透压的大小 * Figure: 05-05 Title: Osmosis in cells. Caption: a. When solutes (such as salt) exist in greater concentration outside the cell than inside, water moves out of the cell by osmosis and the cell shrinks. Here, the fluid surrounding the cell is hypertonic to the cells cytoplasm. b. When solute concentrations inside and outside the cell are balanced, there is a balance of water movement into and out of the cell. Here, the fluid surrounding the cell is isotonic to the cells cytoplasm. c. When solutes exist in greater concentration inside the cell than outside, water moves into the cell by osmosis. This influx may cause animal cells to burst, but plant cells are reinforced with cell walls and thus remain turgid - generally a healthy state for them. Here, the fluid surrounding the cell is hypotonic to the cells cytoplasm. * 先自学初识结构和功能，然后视图认出胞器，交流归纳法，内膜系统简介，和内共生学说，双手画 全完以后，问还却什么？支架系统，信号系统， * 大小， 动植物细胞的区别 细胞学说 细胞是有机体，一切动植物都是由单细胞发育而来 所有细胞在结构和组成上基本相似 新细胞是由已存在的细胞分裂而来 细胞是生物体结构和功能的基本单位 生命的结构基础 除病毒外，细胞是一切生物的结构和功能的基本单位 真核细胞 动物细胞