Chapter 5 The movement of substances △ cross Cell membranes Learning objectives: 1. Principles of membrane transport: 2. Passive transport and active transport; 3. Two main classes of membrane transport proteins. Carriers and Channels: 4. The ion transport systems 5. Endocytosis and Phagocytosis: cellular uptake of macromolecules and particles
Chapter 5 Learning Objectives: 1. Principles of membrane transport; 2. Passive transport and active transport; 3. Two main classes of membrane transport proteins: Carriers and Channels; 4. The ion transport systems; 5. Endocytosis and Phagocytosis: cellular uptake of macromolecules and particles. The Movement of Substances Across Cell Membranes
1. Principles of membrane transport A. The plasma membrane is a selectively permeable barrier. It allows for separation and exchange of materials across the plasma membrane. B. The protein-free lipid bilayers are highly impermeable to ions C. The energetics of solute movement: Diffusion is the spontaneous movement of material from a region of high concentration to a region of low concentration .The free-energy change during diffusion of nonelectrolytes depends on the concentration grdient The free-energy change during diffusion of electrolytes depends on the electrochemical gradient
1. Principles of membrane transport A. The plasma membrane is a selectively permeable barrier. It allows for separation and exchange of materials across the plasma membrane. B. The protein-free lipid bilayers are highly impermeable to ions. C. The energetics of solute movement: vDiffusion is the spontaneous movement of material from a region of high concentration to a region of low concentration. vThe free-energy change during diffusion of nonelectrolytes depends on the concentration grdient. vThe free-energy change during diffusion of electrolytes depends on the electrochemical gradient
D. Transport processes within an eukaryotic cell Carrier protein membrane Mitochondrion Dicarboxylic Tricarboxylic acids c dGT Succinate 「Fat Glyoxysome Peroxisome Serine Amino acids
D. Transport processes within an eukaryotic cell
2. Passive transport and active transport A.onic differentiation inside and outside cell TABLE I I-I A Comparison of lon Concentrations Inside and Outside a Typical Mammalian Cell COMPONENT INTRACELLULAR EXTRACELLULAR CONCENTRATION(mM) CONCENTRATION (mM) Cations Na+ 5-15 145 40 Mg2+ 0.5 10 7×105(10-72 M or pH7.2)4×105(10-74 M or pE7.4) 15 110 The cell must contain equal quantities of positive and negative charges( that is, be electrically neutral). Thus, in addition to cl-, the cell contains many other anions not listed in this table; in fact most cellular constituents are negatively charged(HCO3, PO43. proteins, nucleic acids, metabolites carrying phosphate and car boxyl groups, etc. ).The concentrations of Ca2+ and Mg2+ given are for the free ions. There is a total of about 20 mM Mg+ and 1-2 mM Ca in cells, but this is mostly bound to proteins and other substances and for Ca2+, stored within various organelles
2. Passive transport and active transport A.Ionic differentiation inside and outside cell
B Comparison of two classes of transport Table 8-2 Properties of Passive and Active Transport Diffusion(Passive Transport) Properties Simple Diffusion Facilitated Diffusion Active Transport Solutes transported Examples Small nonpolar Yes Large nonpolar Fatty acids Ye N Small polar Yes №№mee No Large polar Glucose lons N+ K+ C Thermodynamic properties Direction relative to electrochemical gradient Down Effect on entropy Increased Increased Decreased Metabolic energy required Intrinsic directionality Kinetic properties Carrier-mediated Michaelis- Menten kinetics Competitive inhibition sss es 0 es
B. Comparison of two classes of transport