4. Introduction General Characteristics Lipid solubility Lipid soluble materials should cross due to non-polar tails of phospholipids Size “size matters” Restricts larger molecules Charge/Polarity Charged materials won’t cross Think of ions Channels/Carriers For ions, aquaporins for water (at least 10 different types) Aquaporin shown on right http://arbl.cvmbs.colostate.edu/hbooks/molecules/aquaporins.html
5. Passive Non-energy requiring Movement must be favorable High concentration to low concentration Examples Simple diffusion Osmosis Filtration Facilitated diffusion (could be active as well but then usually referred to as solute pumping) Fig. 3.14 Types of transport
6. Active Active Transport energy requiring Movement is non- favorable Low concentration to high concentration Examples Solute pumping Vesicular transport Fig. 3.19 Types of transport
8. Simple Diffusion Movement by random motion Brownian movement Favored by the existence of a concentration gradient from one area to another [solute] = osmolarity Diffusion goes from high osmolarity to low osmolarity Eventually dynamic equilibrium is reached Fig. 3.14 Passive Processes
9. Simple Diffusion Factors affecting diffusion Temperature Higher the temp. the faster it occurs Size Smaller molecules diffuse faster SEE GELATIN DEMO 294 vs. 738 Magnitude of the concentration gradient Greater the gradient the faster diffusion occurs Fig. 3.14 Passive Processes
10. Simple Diffusion If a membrane is involved then the following are factors Membrane surface area More surface area = greater diffusion Think apical end of some epithelial cells. WHY? Membrane permeability E.g. potassium ions diffuse easier through a cell membrane than sodium ions Campbell et al., Fig. 5.11 Passive Processes
11. Simple Diffusion What crosses the cell membrane via simple diffusion? H2O, O2, CO2, N2 Steroids, fat soluble vitamins Urea, glycerol, small alcohols, NH3 Campbell et al., Fig. 5.11 Passive Processes
13. Fick’s Law Gives variables that affect diffusion Rate of transfer αA D (C1-C2) T Think of general mathematical relationships of numerator vs. denominator You will come back to this in the respiratory system in 1206 (A=area; T=thickness of barrier; D=diffusion constant; (C1-C2)= concentration difference
15. Osmosis Low Osmolarity High Osmolarity high [H2O] low [H2O] membrane Direction of water flow Passive Processes Diffusion of water through a semi-permeable membrane (solute won’t cross) Water diffuses down its concentration gradient
16. Osmosis Net Diffusion of water Passive Processes Start: 67% solution Start: 33% solution Water Solute Water loss Water gain End: 50% solution End: 50% solution
18. Osmosis Direction of water flow Passive Processes Equilibrium Low Osmolarity High Osmolarity high [H2O] low [H2O] membrane
19. Osmosis Osmotic Pressure Pressure of a solution due to drawing in water It can be measured We will study this in 1206 when we study capillary dynamics Fig. 3.15 Passive Processes
20. Osmosis 10% solution(hypertonic) 5% solution(hypotonic) Some new terms Is a 5% solution a lot? Depends upon what is being compared to There are terms to describe relative concentrations Hypertonic Has more dissolved material (solute) than another solution Hypotonic Has less dissolved material (solute) than another solution In this case the 5% is hypertonic. If comparing it to 10%, the 5% would be hypotonic Passive Processes 5% solution(hypertonic) .9% solution(hypotonic) Modified fromhttp://proto.thinkquest.nl/~llb082/nl/?thepage=hst1
21. Osmosis Isotonic is when both solutions contain the same solute concentration Passive Processes 3 % solution 3 % solution Modified fromhttp://proto.thinkquest.nl/~llb082/nl/?thepage=hst1
22. Osmosis Hypotonic Hypertonic high [H2O] low [H2O] membrane Direction of water flow Passive Processes Hypertonic More solute; less water Hypotonic Less solute; more water Therefore, water always flows from the hypotonic to the hypertonic
23. Direction of water flow Passive Processes Equilibrium Hypotonic Hypertonic high [H2O] low [H2O] membrane
24. Campbell et all, Fig. 5.12 Passive Processes Isotonic 1% sucrose solution (hypotonic) 10% sucrose solution (hypertonic)
25. Passive Processes Tonicity and Red Blood Cells Hypotonic Isotonic Hypertonic Cells Swell Crenation Cells Shrink Low Osm High Osm Osm Net H2O OUT Net H2O IN High Osm Osm Low Osm Fig. 3.16
27. Osmosis Net Diffusion of water Passive Processes Start: 67% solution Start: 33% solution Water Solute Water loss Water gain End: 50% solution End: 50% solution
28. Filtration Movement of substances across a membrane due to hydrostatic pressure (or gravity as shown on the right) Capillary fluid movement kidneys Passive Processes
30. Facilitated diffusion Transport is facilitated by a membrane protein Carrier mediated facilitated diffusion Protein acts as a carrier Passive since the movement is still high low and no ATP is used Fig. 3.18 Passive Processes
32. Facilitated diffusion Rate of movement is due to the number of carriers Saturation can occur so a transport maximum is reached Passive Processes Fig. 3.17
33. Facilitated diffusion Types of carriers (can be active or passive) Uniport Carries only one solute at a time e.g. Calcium pump (Active) Symport Carries 2 or more solutes through simultaneously e.g. sodium and glucose in the intestine and kidney Antiport Carries two or more solutes in opposite directions Called countertransport e.g. sodium-potassium pump (active) Passive Processes http://www.vscht.cz/eds/knihy/uid_es-002/motor/index.obrazky.html
