Solutes & Water Chapter 4

Transcription

1 4 th Lecture, 23 Jan 2009 Vertebrate Physiology ECOL 437 (MCB/VetSci 437) Univ. of Arizona, spring 2009 Solutes & Water Chapter 4 Kevin Bonine & Kevin Oh 1. Finish Molecules, Membranes, etc. 2. Solutes & Water 1 Housekeeping, 23 January 2009 Readings Today: Chapters 2 & 4 Mon 26 Jan: Chapters 4 & 11 Wed 28 Jan: Chapter 11 LAB Wed 28 Jan: Bisbal & Specker 1991 (see website for links to papers) Fri 30 Jan: Chs 11 & 12 Lab discussion leaders: 04 Feb 1pm Carlos?, Michelle 3pm Maria, Jay Lab discussion leaders: 28 Jan 1pm Steve, Ami 3pm Ty, George 2 1

2 TODAY 3 TODAY! 4 2

3 Vertebrate Physiology 437 Chapter 4 Movement of Solutes and Water 5 What are the different ways to get substances across membranes? 6 3

4 Movement Across Membranes 1. Passive Diffusion (= simple diffusion) 2. Passive Transport (= facilitated diffusion) 3. Active Transport Transport (pore or carrier) may be highly selective 417 Randall et al How does a channel act selectively? 8 4

5 Ion Channels Ion selectivity Leaky channels (e.g., K) Voltagegated channels (e.g., Na, K, Ca) Ligandgated channels Mechanically activated channels, etc. charge ease of dehydration size 429 Randall et al Movement Across Membranes 1. Passive Diffusion (= simple diffusion) nonpolar/nonelectrolyte lipid soluble (steroid hormones) few H bonds ~smaller size rate depends on [ ] gradient No saturation 417 Randall et al

6 Diffusion Fick Equation: J = D C 1 C 2 X J = net rate of diffusion per unit area D = diffusion coefficient (depends on permeability and Temp) C 1 C 2 = [gradient] X = distance separating C1 from C2 11 Origin of Circulatory Systems! Hill et al

7 Movement Across Membranes 1. Passive Diffusion (= simple diffusion) 2. Passive Transport (= facilitated diffusion) Down Electrochemical gradient A. pore B. carrier mediated pores show some saturation, but not as much as carriers Randall et al Movement Across Membranes 1. Passive Diffusion (= simple diffusion) 2. Passive Transport (= facilitated diffusion) 3. Active Transport (1 o, 2 o ) 417 Randall et al Randall et al Na/K ATPase Pump 14 7

8 El Nino lack of food Starvation Animals may lose 15% body length bone absorption Only adult vertebrate known to regularly shrink (astronauts?) Largest animals die natural selection vs. sexual selection (Most efficient salt glands known in reptiles) Galapagos Marine Iguana (Iguanidae) high cost of salt excretion Amblyrhynchus cristatus 17 K.E.Bonine 2004 Reptilian Salt Glands 18 8

9 In Freshwater Hill et al (See Bisbal & Specker 1991) Hill et al

10 Membrane Selectivity (Channels) 429 Randall et al Charge, ease of dehydration, size Diffusion nonpolar/nonelectrolyte lipophilic few H bonds smaller size Transport rates depend on 1. electrochemical gradient 2. # carriers/pores Randall et al Movement Across Membranes 420 Randall et al Randall et al How is this related to the early test for diabetes?? 22 10

11 Movement Across Membranes 422 Randall et al Movement Across Membranes 426 Randall et al How would you describe this movement across membrane? 24 11

12 424 Randall et al Na/K ATPase Pump 25 Movement Across Membranes How does glucose cross membranes? Most tissues: Passive transport down [ ] gradient via carrier proteins In gut: 2 o active to move Glu against [ ] gradient into blood from food 26 12

13 Hill et al Leinhard et al

14 Osmotic Properties of Cells and Relative Ion Concentrations K Ca Ca 412 Randall et al Na K Cl Cl Na Permeabilities K >> Na ; Cl A (includes proteins, phosphate groups, etc.) 29 Electrogenic vs. Electroneutral? Hill et al

15 Ion Gradients as an Energy Source CET example: Metabolism Electron Transport Chain ATP creation energy currency Glucose > Glycolysis > Pyruvic Acid > Krebs Cycle > NADH2, FADH2 > Electron Transport Chain > Oxygen final electron acceptor Result: H2O, Proton Gradient > Oxidative Phosphorylation > ATP 1 Move molecules (see p.170 Hill 2008) 2 Electrical Signalling 3 Chemiosmotic Energy Transduction 427 Randall et al Randall et al Just add water How does water move across membranes? Aquaporins (Diffusion) 32 15

16 Movement Across Membranes Iso Hypo osmotic Hyper In specific tissues and cells: Iso Hypo tonic Hyper Movement of water 414 Randall et al Osmotic Properties of Cells and Relative Ion Concentrations K Ca Ca Na K Cl Cl Na 412 Randall et al Hypertonic Cell Contents 416 Randall et al

17 Colligative Properties Osmotic Pressure Freezing Point Water Vapor Pressure (boiling point; evaporation) Hill et al Hill et al

18 Osmolarity 6 x osmolar solution (Osm) has 1 Avogadro s number of dissolved particles/ liter solvent 1 milliosmolar solution (mosm) has Avogadro s number of dissolved particles/ liter solvent 37 What osmolarity do you get if you add 6 x molecules of glucose to a liter of water? What osmolarity do you get if you add 6 x molecules of table salt to a liter of water? NaCl (strong electrolyte) 38 18

19 Osmotic Pressure Vs. Hydrostatic Pressure Hill et al Difference in osmotic potential Rate of Osmosis = K П 1 П 2 X Proportionality Coefficient (~ permeability and temp) Distance between solutions 40 19

20 Electrochemical equilibrium Fig 3.6, Hill et al Movement Across Membranes Electrochemical Gradient 1. Electrical gradient 2. Concentration gradient K K Electrochemical equilibrium Equilibrium potential (E x in mv) Na when [X] gradient = electrical gradient Na 42 20

21 Equilibrium potential (E x in mv) Every ion s goal in life is to make the membrane potential equal its own equilibrium potential (E x in mv) 43 21