Unit Two: Membrane Physiology, Nerve, and Muscle Chapter 4: Transport of Substances Through Cell Membranes Guyton and Hall, Textbook of Medical Physiology, 12th edition

Fig. 4.1 Chemical Compositions of extracelluar and intracellular fluids

Through the cell membrane Diffusion Diffusion Through the cell membrane

Diffusion of lipid soluble substances Diffusion (cont.) Diffusion of lipid soluble substances Diffusion of water and other lipid-insoluble substances Diffusion through protein pores and channels Selective permeability of protein channels Fig. 4.4 Structure of a potassium channel

Gating of protein channels (voltage and chemical) Diffusion (cont.) Gating of protein channels (voltage and chemical) Open state vs. closed state Fig. 4.5 Transport of sodium and potassium through protein channels

Facilitated Diffusion Diffusion (cont.) Facilitated Diffusion Fig. 4.7 Effect of concentration on the rate of diffusion by simple diffusion and facilitated diffusion

Fig. 4.8 Postulated mechanism for facilitated diffusion

Factors Affecting the Net Rate of Diffusion Net diffusion rate is proportional to the concentration difference across a membrane. Effect of membrane electrical potential on diffusion of ions---the Nernst equation Effects of pressure differences across the membrane

Fig. 4.9 Effect of concentration difference electrical potential difference affecting negative ions, (B) pressure difference, (C) to cause diffusion of molecules and ions through a cell membrane.

Osmosis: “Net” Diffusion of Water Fig. 4.10 Osmosis at a cell membrane when a sodium chloride solution is placed on one side of the membrane and water is placed on the other side.

Importance of the number of osmotic particles (molar concentration) Osmosis (cont.) Osmotic Pressure Importance of the number of osmotic particles (molar concentration) Osmolality: 1 gram molecular weight of osmotically active solute c. Relation of osmolality to osmotic pressure

Osmosis (cont.) Fig. 4.11 Osmotic pressure caused by osmosis at a semipermeable membrane

Active Transport Primary Active Transport Na+-K+ pump

Active Transport (cont.) b. Na+-K+ pump is important in controlling cell volume c. Electrogenic nature of the Na+-K+ pump Primary active transport of calcium Primary active transport of hydrogen ions Energetics of primary active transport

Secondary Active Transport Co-transport of glucose and amino acids along with sodium ions

Secondary active transport (cont.) Sodium Counter-transport of Calcium and Hydrogen Ions

Fig. 4.15 Basic mechanism of active transport across a layer of cells.