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细胞是构成人体的最基本的功能单位。人体的细胞可根据结构和功能分成二百余种，但许多基本的功能活动是共同的，包括：

第二章 细胞的基本功能. 细胞是构成人体的最基本的功能单位。人体的细胞可根据结构和功能分成二百余种，但许多基本的功能活动是共同的，包括：. 细胞膜的物质转运功能 ； 细胞的信号转导功能； 细胞膜的生物电现象； 肌细胞的收缩活动。. 第一节 细胞膜的结构和物质转运功能. Chap. 1 Cellular Membranes and Trans-membrane Transport of Solutes and Water. from Berne & Levy Principles of Physiology

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细胞是构成人体的最基本的功能单位。人体的细胞可根据结构和功能分成二百余种，但许多基本的功能活动是共同的，包括：

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  1. 第二章 细胞的基本功能 细胞是构成人体的最基本的功能单位。人体的细胞可根据结构和功能分成二百余种，但许多基本的功能活动是共同的，包括： • 细胞膜的物质转运功能 ； • 细胞的信号转导功能； • 细胞膜的生物电现象； • 肌细胞的收缩活动。

  2. 第一节 细胞膜的结构和物质转运功能 Chap. 1 Cellular Membranes and Trans-membrane Transport of Solutes and Water from Berne & Levy Principles of Physiology (4th ed) 2005

  3. through pores passive ion channels carriers symport active antiport across • simple diffusion • facilitated diffusion • primary active transport • secondary active transport • endocytosis & exocytosis

  4. Cell membrane or plasma membrane serves as a permeability barrier that allows the cell to maintain a cytoplasmic composition far different from the composition of the extracellular fluid. • The membranes that enclose the various organelles divide the cell into discrete compartments and allow the localization of particular biochemical processes in specific organelles.

  5. 1. Membrane Structure & Composition • Membrane Structure • lipid bilayer

  6. fluid mosaic model

  7. phospholipids • lipids cholesterols sphingolipids integral membrane proteins • proteins peripheral membrane proteins • Membrane Composition • glycolipids & glycoproteins

  8. 2. Transmembrane Transport • Simple Diffusion

  9. Properties of Protein-mediated Transport • More rapidly than by simple diffusion • Saturation kinetics:as the concentration of the transported compound is increased, the rate of transport at first increases, but eventually a concentrations reached after which the transport rate increases no further. • Chemical specificity:only molecules with the requisite chemical structure are transported. • Competitive inhibition: structurally related molecules may compete for transport.

  10. Facilitated Diffusion • occurs via a membrane protein that is not linked to metabolic energy. • cannot move substances against concentration gradients. • via pores, via ion channels or via carriers.

  11. via pores

  12. via ion channels

  13. via carriers

  14. Active Transport • primary active transporthas adirect link to metabolic energy, via ion pumps or ATPases.

  15. secondary active transport derives energy from the concentration gradient of another substance that is actively transported, via symporter or antiporter (exchanger).

  16. Endocytosis and Exocytosis

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