The Cellular Level of Organization

1. The Cellular Level of Organization 1

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3. Cells are measured in micrometers. Cells vary in size and shape. Shape is determined by function. Two types of cells: Sex cells Somatic (body) cells Cells are surrounded by extracellular fluid, which is called interstitial fluid in most tissues 3

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9. Plasma membrane Physical isolation Regulation of exchange with the environment Sensitivity to the environment Signal transduction Structural support 9

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13. Membrane carbohydrates 3-5 % of membrane Proteoglycans, glycoproteins and glycolipids Gylcocalyx Lubrication and protection Anchoring and locomotion Specificity in binding Recognition 13

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17. Membrane proteins Anchoring proteins Recognition proteins Enzymes Receptor proteins Carrier proteins Channels 17

18. Intercelluar junctions Tight junctions � membranes of adjacent cells bound together by occludins and claudins formingAn impermeable junction. Desmosomes are protein �spot welds� in skin and cardiac muscle: plaques, linker protein filaments, and thicker filaments across inside of cell 18

19. Intercellular junctions Gap junctions are tubular channels (connexons) that connect the cytoplasm of one cell with that of another. Ions, simple sugars and other small molecules Cellular Adhesion Molecules help cells form temporary attachments to other cells. CAMs 19

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22. Membrane proteins Anchoring proteins Recognition proteins Enzymes Receptor proteins Ligands bind Carrier proteins allows establishment of electrochemical gradient Channels Rafts �lipid rafts � tails saturated; more cholesterol 22

23. Membrane Physiology Cell membrane function: Cellular communication Establish an electrochemical gradient Are selectively permeable Lipids Size Electrical charge Presence of channels and transporters 23

24. Movement of materials Passive processes: Depend on concentration and kinetic energy Do not require energy Move substances from an area of high concentration to an area of low concentration Down a concentration gradient 24

25. Diffusion Rate depends on: Temperature Gradient size Distance Molecule size Electrical forces Reaches equilibrium or Physiological steady state 25

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28. Simple diffusion Channel mediated diffusion 0.8 nm Size and charge Interaction between ion and channel walls Rate limited by number of suitable channels - Na, K, Cl pass through membranes at a rate comparable to simple diffusion 28

29. Osmosis Movement of WATER through a selectively permeable membrane Moves according to the conc. of water Osmotic pressure 29

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31. Tonicity Concentration of one solution relative to another ( conc. in cytoplasm) Isotonic � equal concentrations 0.9 % NaCl or 5% glucose soln. Hypertonic � more concentrated Hypotonic � less concentrated 31

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36. osmosis Eliminates conc. differences faster than solute diffusion Aquaporins - water channels 36

37. Facilitated diffusion Uses carrier molecules Down a conc. gradient Specificity Saturation limits regulation 37

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39. Filtration 39

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42. Active Transport Depends on the use of energy (ATP) Moves substances up a concentration gradient (up hill) These systems are often called �pumps� Na+ / K+ pump - Na/K ATPase Others carry Ca++, Mg++, I-, Cl- and Fe++ 42

43. Active transport Countertransport Exchange pump Cotransport or symport Move two different substances in same direction One down a conc. Gradient Use of energy to pump one substance back out 43

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45. Vesicular Transport 45

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48. Receptor mediated endocytosis 48

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50. Exocytosis 50

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