MEMBRANE PHYSIOLOGY Chapter 3FLUID MOSAIC MODEL ¢ Phospholipid Bilayer ¢ Embedded Proteins ¢ Cholesterol ¢ CarbohydratesSKELETAL FENCE MODEL ¢ Membrane proteins are constrained ! Tethered to the membrane skeleton (like a dog on a leash) ! Limited by the membrane skeleton (like a dog within a fenced yard)DIFFUSION ¢ The movement of solutes from an area of high concentration to an area of low concentration ¢ Equilibrium occurs when all connected areas are similar in concentrationCONDUCTIONOSMOSISOSMOTIC CONCENTRATION ¢ Molarity is a measure of moles of solute per volume (liter) of solution ¢ Osmolarity is a measure of osmoles of solute particles per volume (liter) of solution ¢ Because some solutes disassociate in water, one mole is not necessarily one osmole. ¢ 1 Mol of NaCl = 2 Osm of ions (Na+ and Cl-)OSMOTIC CONCENTRATION & TONICITY ¢ Osmolarity and tonicity are related, but different concepts. ! Both can compare the solute concentrations of two solutions separated by a membrane. ! Osmolarity ¢ Takes into account the total concentration of all solutes, including both penetrating solutes and non-penetrating solutes ¢ Osmolarity is a property of a solution and is independent of any membrane ! Tonicity ¢ Takes into account the total concentration of only non-penetrating solutes ¢ Tonicity is a property of a solution with respect to a particular membraneOSMOTIC CONCENTRATION & TONICITY WaterOSMOTIC CONCENTRATION & TONICITY WaterOSMOTIC CONCENTRATION & TONICITY WaterOSMOTIC CONCENTRATION & TONICITYMEMBRANE CHANNEL ¢ Allow movement of particles through the membrane ¢ Ions ¢ Water ¢ Other Solutes ¢ Passive Transport ¢ Active TransportPRIMARY ACTIVE TRANSPORTSECONDARY ACTIVE TRANSPORTVESICULAR TRANSPORTVESICULAR TRANSPORTMEMBRANE POTENTIALLIGANDS ¢ Intercellular Chemical Messengers ! Must bind to receptors on target cells ! Six Main Types ¢ Paracrines ¢ Short ranged, simple diffusion ¢ Target adjacent cells ¢ Neurotransmitters ¢ Short ranged, released by neurons in response to an electrical signal ¢ Targets a neurons, muscle, or gland ¢ Hormones ¢ Long ranged via circulatory system ¢ Secreted by endocrine glands ¢ Neurohormones ¢ Long ranged via circulatory system ¢ Secreted by neurosecretory neurons ¢ Pheromones ¢ Released into the environment by glands ¢ Target other animals of the same species ¢ Cytokines ¢ Regulatory peptides generally involved in development or immunity ¢ May be short-ranged or long-ranged ¢ Can be made by nearly any