Membrane transport Xia Qiang, PhD Department of physiology Zhejiang University School of Medicine Tel:88206417,88208252 Email:xiaqiang@zju.edu.cn
Membrane Transport Xia Qiang, PhD Department of Physiology Zhejiang University School of Medicine Tel: 88206417, 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
opyright e The McGraw-Hill Companies, Ine. Permission roquirod for reproduction or display. Nucleus Nucleolus Plasma membrane endoplasmic reticulum Bound ribosomes Fre endoplasmic Microfilaments Microtubule Organelles have their own membranes
Organelles have their own membranes
Cell Membrane (plasma membrane) Copy right g The McGraw-Hill Companies, Inc. Permission required for reproduct on or display. TABLE 3-1 Functions of Cell Membranes 1. Regulate the passage of substances into and out of cells and between cell organelles and cytosol 2. Detect chemical messengers arriving at the cell surface 3. Link adjacent cells together by membrane junctions 4. Anchor cells to the extracellular matrix
Cell Membrane (plasma membrane)
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）
Importance of pumps, transporters A channels Basis of physiologic processes Growth Metabolic activities Sensory perception Basis of disease Defective transporters(cystic fibrosis) Defective channels (long QT syndrome, paralysis) Basis of pharmacological therapies Hypertension (diuretics) Stomach ulcers (proton pump inhibitors)
Importance of pumps, transporters & channels • Basis of physiologic processes ▫ Growth ▫ Metabolic activities ▫ Sensory perception • Basis of disease ▫ Defective transporters (cystic fibrosis) ▫ Defective channels (long QT syndrome, paralysis) • Basis of pharmacological therapies ▫ Hypertension (diuretics) ▫ Stomach ulcers (proton pump inhibitors)
START: Initially higher concentration of molecules randomly move toward lower concentration Over time solute molecules Q Q placed in a solvent 0 o989。0090。oooo 0。 will evenly distribute themselves 0090. o 00 o Diffusional equilibrium 90000o°。°o。。°°°。°。°。° is the result Q o。o。oo Q (Part b). 0。o 0000ooo 0o。oo0 o oo oo o o0009 0。o
Over time, solute molecules placed in a solvent will evenly distribute themselves. START: Initially higher concentration of molecules randomly move toward lower concentration. Diffusional equilibrium is the result (Part b)
At time B, some glucose has crossed into side 2 as some cross into side 1 Copyright@ The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Time A Time B Time C EEc Compartment 1 oc60009元 Compartment 2
At time B, some glucose has crossed into side 2 as some cross into side 1
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