Membrane transport跨膜转运 Xia Qiang(夏强),PhD Department of Physiology Zhejiang University School of Medicine Tel:88208252 Email:xiaqiang@zju.edu.cn
Membrane Transport 跨膜转运 Xia Qiang（夏强）, PhD Department of Physiology Zhejiang University School of Medicine Tel: 88208252 Email: xiaqiang@zju.edu.cn
LEARNING OBJECTIVES Describe how solutes cross cell membranes Explain how charge size and solubility affect solute movement across cell membranes Contrast how transporters, pumps channels work Describe how ion channels are gated Describe how epithelial transport works
LEARNING OBJECTIVES • Describe how solutes cross cell membranes • Explain how charge, size, and solubility affect solute movement across cell membranes • Contrast how transporters, pumps & channels work • Describe how ion channels are gated • Describe how epithelial transport works
Membrane Transport Simple diffusion(单纯扩散) Facilitated Diffusion(易化扩散) Active Transport(主动转运) Endocytosis and exocytosis(出胞与入胞)
Membrane Transport ▫ Simple Diffusion（单纯扩散） ▫ Facilitated Diffusion（易化扩散） ▫ Active Transport（主动转运） ▫ Endocytosis and Exocytosis（出胞与入胞）
Solute racellular flu Electrochemical gradient x X Intracellular fluid nergy Simple Channel mediated Carrier mediated Active transport diffusion diffusion diffusion A B c E Passive transport (facilitated diffusion)
Compartment 1 impartment 2 High solute concentration Low solute concentration One-way flux∴∴∴∵ One-way flux 器Net小…/八∴∴∴∷ Note: the partition between the two com partments is a membrane that allows this solute to move through it Net flux accounts for solute movements in both directions
Note: the partition between the two compartments is a membrane that allows this solute to move through it. Net flux accounts for solute movements in both directions
Simple Diffusion Relative to the concentration gradient movement is doWn the concentration gradient ONLY (higher concentration to lower concentration) (outside) lipid- soluble molecules Rate of diffusion depends on O2, CO2, H2O The concentration gradient Charge on the molecule Size Lipid solubility 0888 (inside)
Simple Diffusion Relative to the concentration gradient movement is DOWN the concentration gradient ONLY (higher concentration to lower concentration) Rate of diffusion depends on • The concentration gradient • Charge on the molecule • Size • Lipid solubility
Simple diffusion &t gap junctions [High [LoW Ca++
Simple diffusion & gap junctions
Facilitated diffusion Carrier-mediated Protein Solute molecules transporte Uniport Symport Anti port
Facilitated Diffusion ▫ Carrier-mediated
Simple diffusion Facilitated diffusion Characteristics of carrier-mediated diffusion net movement always depends on Concentration of S outside cel the concentration gradient Specificity Saturation When S1 is alone Competition In presence of $2 Concentration outside cel
Characteristics of carrier-mediated diffusion net movement always depends on the concentration gradient ▫Specificity ▫Saturation ▫Competition
Channel-mediated Copyrighte The McGraw a Componies, Inc, Permission required tor reproduction cr os round for re 3 3 cartoon models of Copyright e The McGraw-Hill Companies, Inc. Permission required for reproduction or display on channel integral membrane proteins that function as ion channels: the regulated opening and closing of these channels is Cross section the basis of how neurons function queous pore of ion channel
– Channel-mediated 3 cartoon models of integral membrane proteins that function as ion channels; the regulated opening and closing of these channels is the basis of how neurons function