Cellular Transport Notes (Text 7.2 p 175-178 & 8.1 p 194-200)

1. Cellular Transport Notes(Text 7.2 p 175-178 & 8.1 p 194-200)

2. Definitions • Cell membranes are completely permeable to water. • The environment the cell is exposed to can have a dramatic effect on the cell. • Solutions are made of solute and a solvent • Solvent - the liquid (water) into which the solute is poured and dissolved.

3. Definitions • Solute: substance that is dissolved or put into the solvent (water). • Common cell solutes include salts, sugars, some minerals (iron ions and calcium ions) and protons (electrons from acids). • Eg. Sodium chloride dissolved in water makes a saline solution. The sodium chloride is the solute. The water is the solvent.

4. Concentration amount of solute per unit volume of solution. expressed in mass/volume (g/100ml - percentage), ppm (parts per million), and moles/volume (molarity). The greater the mass or moles per unit volume, the more concentrated the solution.

5. Concentration Gradient • Difference in concentration between solute molecules from area high concentration to area of low concentration. • The greater the difference the faster the rate of diffusion and vice versa • i.e. the steeper the hill

6. Cellular MembraneStructure and Function • All cells have a cell membrane • Chiefly responsible for maintaining homeostasis inside a living cell using different methods to transport molecules in and out of the cell. TEM picture of a real cell membrane.

7. Cellular MembraneStructure and Function • Too much water can burst the cell • Too many wastes can poison the cell • The cell cannot tolerate any great variations in ion conditions. TEM picture of a real cell membrane.

8. Jobs of the Cell Membrane • Provides protection and support for the cell • Regulate the exchange of substances (gases and ions) • Communicates with other cells • Identification (proteins and carbohydrates on its surface) TEM picture of a real cell membrane.

9. http://www.goldiesroom.org/AP%20Biology/AP%20Lecture%20Notes%20pdf/LN014--Ch05--Cell%20Transport.pdfhttp://www.goldiesroom.org/AP%20Biology/AP%20Lecture%20Notes%20pdf/LN014--Ch05--Cell%20Transport.pdf

10. http://www.goldiesroom.org/AP%20Biology/AP%20Lecture%20Notes%20pdf/LN014--Ch05--Cell%20Transport.pdfhttp://www.goldiesroom.org/AP%20Biology/AP%20Lecture%20Notes%20pdf/LN014--Ch05--Cell%20Transport.pdf

11. Fluid Mosaic Model of the cell membrane Polar heads love water & dissolve Membrane movement animation Non-polar tails hide from water Carbohydrate cell markers Proteins

12. Fluid Portion Lipid Bilayer - 2 phospholipid layers • Phosphate head is polar (hydrophilic – water loving) • Fatty acid tails non-polar(hydrophobic – water fearing) • Proteins embedded in membrane Phospholipid Lipid Bilayer

13. Cell Membrane Pores • Selectively permeable: Allows some molecules in and keeps other molecules out • The structure helps it be selective! Pores

14. Lipid Bilayer Outside of cell (interstitial) Carbohydrate chains Proteins Transport Protein Phospholipids Inside of cell (cytoplasm) Animations of membrane structure Go to Section:

15. http://www.goldiesroom.org/AP%20Biology/AP%20Lecture%20Notes%20pdf/LN014--Ch05--Cell%20Transport.pdfhttp://www.goldiesroom.org/AP%20Biology/AP%20Lecture%20Notes%20pdf/LN014--Ch05--Cell%20Transport.pdf

18. The different components of a plasma membrane are integral proteins, peripheral proteins, glycoproteins, phospholipids, glycolipids, and in some cases cholesterol, and lipoproteins. • Construction of the Cell Membrane - Learning Activity • detailed cell membrane animation

19. Proteins Embedded in Membrane Serve Different Functions • Transport Proteins • regulate movement of substance • Channel Proteins • form small openings for molecules to diffuse through like water • Carrier Proteins • binding site on protein surface "grabs" certain molecules and pulls them into the cell animation

20. Gated Channels • similar to carrier proteins, not always "open"—eg. Bind and pull in calcium ions when needed. This requires cell energy—active transport.

21. Receptor Proteins • molecular triggers that set off cell responses (such as release of hormones or opening of channel proteins) • e.g. The junction between nerve cells requires the transmission of neurotransmitters between synaptic gaps—these chemicals bind onto receptor proteins.

22. Recognition Proteins - ID tags, to identify cells to the body's immune system (called antigens)

23. TRANSPORT MECHANISMS • PASSIVE TRANSPORT • ACTIVE TRANSPORT • ENDOCYTOSIS • EXOCYTOSIS

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

25. Passive Transport (p 198) • cell uses no energy • molecules move randomly • Molecules spread out from an area of high concentration to an area of low concentration. • i.e. down a concentration gradient • (High  Low) • Passive Transport Animation

26. 3 Types of Passive Transport • Diffusion – high conc. to low conc. • Facilitative Diffusion – diffusion with the help of transport proteins • Osmosis – diffusion of water

27. 1. Diffusion Animation • random movement of particles from an area of high concentration to an area of low concentration. (High to Low) • Diffusion continues until all molecules are evenly spaced (equilibrium is reached) • Note: molecules will still move around but stay spread out. http://bio.winona.edu/berg/Free.htm

28. 1. Diffusion

29. 2. Facilitated Diffusion A B Facilitated diffusion(Channel Protein) Diffusion (Lipid Bilayer) • diffusion that is enabled by proteins (channel or carrier proteins) which bind onto required molecules so that they flow into the cell. • Transport Proteins are specific – they “select” only certain molecules to cross the membrane • Transports larger or charged molecules • Animation: How Facilitated Diffusion Works Carrier Protein • http://bio.winona.edu/berg/Free.htm

31. 2. Facilitated Diffusion Glucose molecules Cellular Transport from an area of High High Concentration • Channel Proteins animations Cell Membrane Protein channel Low Concentration Low Transport Protein Through a  Go to Section:

32. 3. Osmosis Animations • Diffusion of water through a selectively permeable membrane • From high to low concentrations • Water moves freely through pores. • Solute (green) too large to move across.

33. 3. Osmosis

34. Factors Affecting Rate of Diffusion 1. Size • small molecules can slip through phospholipids bilayer easier than large molecules • very large molecules may not be able to diffuse at all

35. 2. Concentration • the greater the concentration gradient (bigger range) the quicker a material diffuses (makes the molecules want to move faster) – think of a crowded room • 3. Temperature • In general as temperature increases – molecules move faster which translates into faster diffusion

36. 4. Polarity of molecules • Water-soluble (polar) molecules will not easily move through the membrane because they are stopped by the middle water-insoluble (nonpolar) layer

37. 5. Surface Area • As a cell’s size increases its volume increases much quicker than it’s surface area. • If you double individual lengths (1 cm to 2 cm) the surface areas increases 4 times, and the volume increases 8 times. • If cell size is doubled, it would require 8 times more nutrients and have 8 times s much waste. SA only increases by a factor of 4 – not enough surface area through which nutrients and wastes could move. • Cell would either starve or be poisoned (waste products) • Cells divide before they come too large to function.

38. Active Transport • Involves moving molecules "uphill" against the concentration gradient, which requires energy. • Uses carrier protein molecules as receptors. • One may transport calcium ions another glucose molecules. • Hundreds of these types of protein molecules. • Each one changes shape to accommodate a specific molecule. (Low  High)

39. 2. Active Transport (cont’d) • Their activity can be stopped from transporting molecules with inhibitors (unfortunately, these are usually poisons) which: • either destroy the membrane protein • or just plug it up (e.g. for your neurons – tetanus & botulinum-B secrete a poison that suppress the Na/K pump) • Three types: • active transport animation http://www.biology4kids.com/files/cell2_activetran.html

40. 1. Protein Pumps Sodium Potassium Pumps • transport proteins that require energy to do work • Example: Na+/K+ pumps are important in nerve responses. Protein changes shape to move molecules: this requires energy!

41. Sodium-Potassium Pump • Pumps out 3 sodium atoms for ever 2 potassium atoms taken in against gradient in the cell. ATP and the Na/K Pump Animation: How the Sodium Potassium Pump Works

42. The H+/K+ ATPase • The parietal cells of your stomach (lining) use this pump to secrete gastric juice. • These cells transport hydrogen ions (H+) from a concentration of about 4 x 10-8 M within the cell to a concentration of about 0.15 M in the gastric juice (giving it a pH close to 2). • Recall: pH – power of the H+ ion • Small wonder that parietal cells are stuffed with mitochondria and use huge amounts of energy as they carry out this three-million fold concentration of protons.

43. The H+/K+ ATPase

44. Endocytosis & Exocytosis animations 3. Exocytosis • Moves large, complex molecules such as proteins out of the cell membrane. • Large molecules, food, or fluid droplets are packaged in membrane-bound sacs called vesicles. • Cell changes shape – requires energy • Ex: Hormones or wastes released from cell • Transport Animations

46. 2. Endocytosis • taking bulky material into a cell • Uses energy • Cell membrane in-folds around food particle • “cell eating” • forms food vacuole & digests food • This is how white blood cells eat bacteria!

47. Endocytosis • Endocytosis moves large particles (huge molecules or molecular conglomerates) into a cell. • endo & exocystosis animations

48. Phagocytosis • Phagocytosis is another type of endocytosis used for massive transport.Cell membrane extends out forming pseudopods (fingerlike projections) that surround the particle. • Membrane pouch encloses the material & pinches off inside the cell making a vesicle. • Vesicle can fuse with lysosomes(digestive organelles) or release their contents in the cytoplasm Animation: Phagocytosis HowStuffWorks "Phagocytosis"

49. Used by ameba to feed & white blood cells to kill bacteria.Known as “killer cells"

50. Pinocytosis is another type of endocytosis • Cell membrane surrounds fluid droplets • Fluids taken into membrane-bound vesicle • Known as “cell drinking”