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
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(4th ed)2005
第一节 细胞膜的结构和物质转运功能 from Berne & Levy Principles of Physiology (4th ed) 2005 Chap. 1 Cellular Membranes and Trans-membrane Transport of Solutes and Water
through ● simple diffusion pores passive facilitated diffusion ion channels carriers primary active transport symport active secondary active transport antiport endocytosis exocytosis across
• simple diffusion • primary active transport • endocytosis & exocytosis • facilitated diffusion pores ion channels carriers • secondary active transport symport antiport passive active across through
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
• 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
1. Membrane Structure Composition Membrane structure Choline head lipid bilayer group(polar Fatty acyl chain nonpolar
1. Membrane Structure & Composition ➢ Membrane Structure • lipid bilayer
● fluid mosaic model Outer face Phospholipid Fatty acyl Carbohydrate moiety heads(polar) tails(nonpolar) Cholesterol of glycoprotei bilayer 00b000 Peripheral protein Integral proteins Peripheral protein Inner face with covalent lipid anchor
• fluid mosaic model
Membrane composition phospholipids ● lipids cholesterols sphingolipids integral membrane proteins ● proteins peripheral membrane proteins glycolipids glycoproteins
➢ Membrane Composition phospholipids cholesterols sphingolipids • lipids • glycolipids & glycoproteins • proteins integral membrane proteins peripheral membrane proteins
SMALL 2. Transmembrane CO2 HYDROPHOBIC MOLECULES N2 benzene Transport SMALL H2O UNCHARGED POLAR glycerol ethanol MOLECULES Simple Diffusion LARGER amino acids UNCHARGED POLAR glucose nucleotides MOLECULES H+, Na HCO, K- IONS Ca CI Mg synthetic lipid bilayer
2. Transmembrane Transport ➢ Simple Diffusion
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 n: structurally related molecules may compete for transport
➢ 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
Vmax= maximal rate of transport Mediated transport max 2 Diffusion Km [Transported substance