PowerLecture: Chapter 5

1. A Closer Look at Cell Membranes PowerLecture:Chapter 5

2. CFTR is a protein channel for chloride ions CFTR is a type of ABC transporter in all prokaryotic and eukaryotic cells Impacts, Issues: One Bad Transporter and Cystic Fibrosis ATP ATP Fig. 5.2, p.75

3. Cystic fibrosis, the most common fatal genetic disorder in the U.S., results from a mutation in CFTR gene Impacts, Issues: One Bad Transporter and Cystic Fibrosis

4. Section 5.1: Lipid Bilayer • Basic framework • Selectively permeable • Two layers of phospholipids • Hydrophilic heads • Hydrophobic tails http://www.bioteach.ubc.ca/Bio-industry/Inex/graphics/lipidbilayer.gif

5. Every cell membrane has a mixed composition of phospholipids, glycolipids, sterols, and proteins Most phospholipids and some proteins can drift through membrane Fluid Mosaic Model

7. Overview of Membrane Proteins Receptor Proteins Recognition Proteins Passive Transporters Active Transporters Fig. 5.6, p.79

8. Overview of Membrane Proteins Adhesion Proteins Communication Proteins Fig. 5.6, p.78

9. Span the lipid bilayer Passive Ion selective (nerve and muscle cells) Change shape when they interact with solute GluT1 (glucose transporter) Cotransporter Active Pump solute (calcium pump, ATPase) Transport Proteins

10. Other Proteins Receptor -- Bind an extracellular substance that triggers changes in cell activity Antibody Recognition – ID tags for species HLAs for tissue defense Adhesion – one cell bind to another collagen Communication – channel between 2 cells Cardiac gap junction

11. Section 5.3:Concentration Gradient • Different in #/unit volume of a substances between 2 regions • Will move down “down” gradient

12. Diffusion • Movement of like molecules or ions down a gradient • Molecules move on their own gradient

13. Factors Affecting Diffusion Rate Steepness of concentration gradient Steeper gradient, faster diffusion Molecular size Smaller molecules, faster diffusion Temperature Higher temperature, faster diffusion Electrical or pressure gradients

14. Cell Membranes Show Selective Permeability • Some substances enter, but not others • Vital to maintaining homeostasis • Allows NP • Impermeable to ions & lg Polar

15. Section 5.5:Osmosis Diffusion of water molecules across a selectively permeable membrane • Direction of net flow is determined by water concentration gradient • Side with the most solute molecules has the lowest water concentration

16. Tonicity Refers to relative solute concentration of two fluids Hypotonic - having fewer solutes Hypertonic - having more solutes Isotonic - having same amount

20. Tonicity and Osmosis 2% sucrose solution 1 liter of 10% sucrose solution 1 liter of 2% sucrose solution 1 liter of distilled water Hypotonic Conditions Hypertonic Conditions Isotonic Conditions Fig. 5-13, p.85

21. What type of solution are these cells in? B C A Hypertonic Isotonic Hypotonic

22. Pressure and Osmosis Hydrostatic pressure Pressure exerted by fluid on the walls that contain it The greater the solute concentration of the fluid, the greater the hydrostatic pressure Osmotic pressure Amount of pressure necessary to prevent further increase of a solution’s volume

23. How Organisms Deal with Osmotic Pressure • A protist like paramecium has contractile vacuoles that collect water flowing in and pump it out to prevent them from over-expanding.

24. How organisms deal with Osmotic Pressure • Salt water fish pump salt out of their specialized gills so they do not dehydrate. • Animal cells are bathed in blood. Kidneys keep the blood isotonic by remove excess salt and water. • Bacteria and plants have cell walls that prevent them from over-expanding. In plants the pressure exerted on the cell wall is called tugor pressure.

25. Increase in Fluid Volume first compartment second compartment hypotonic solution hypertonic solution membrane permeable to water but not to solutes fluid volume rises in second compartment Fig. 5.14, p.85

26. Section 5.4:Passive Transport Flow of solutes through the interior of passive transport proteins down their concentration gradients Passive transport proteins allow solutes to move both ways Does not require any energy input

27. Passive Transport glucosetransporter solute (glucose)‏ high low Stepped Art Fig. 5.10, p.80

28. Facilitated Diffusion • Help move specific solutes down the gradient • Can be gated

29. Active Transport Net diffusion of solute is against concentration gradient Transport protein must be activated ATP gives up phosphate to activate protein Binding of ATP changes protein shape and affinity for solute

30. Active • Help specific solutes diffuse against the gradient

31. Active Transport higher calcium concentration ATP Pi ADP Stepped Art Fig. 5-11, p.83

32. Active Transport ATP gives up phosphate to activate protein Binding of ATP changes protein shape and affinity for solute

33. Animations of Active Transport & Passive Transport Weeee!!! high low This is gonna be hard work!! high low Types of Cellular Transport • Passive Transport cell doesn’t use energy • Diffusion • Facilitated Diffusion • Osmosis • Active Transport cell does use energy • Protein Pumps • Endocytosis • Exocytosis

34. Other types Endocytosis (vesicles in)‏ Exocytosis (vesicles out)‏ Fig. 5-9, p.81

35. Section 5.6:Endocytosis and Exocytosis Exocytosis: A cytoplasmic vesicle fuses with the plasma membrane and contents are released outside the cell

36. Endocytosis • A small patch of plasma membrane sinks inward and seals back on itself, forming a vesicle inside the cytoplasm – membrane receptors often mediate this process

37. Macrophage engulfing Leishmania mexicana parasite macrophage Fig 5.17, p.87

38. endocytosis exocytosis a 5.6 Traffic to and From the Cell Endocytosis and Exocytosis coated pit b c d f e Fig. 5-15, p.86

39. How Proteins Get to the Surface vesicle membrane fuses with plasma membrane Golgi body endoplasmic reticulum Fig. 5.18, pg. 87

40. Endocytosis of cholesterol plasma membrane cholesterol