Ch 5 PowerPoint Biology 201

Please download to get full document.

View again

of 45
13 views
PDF
All materials on our website are shared by users. If you have any questions about copyright issues, please report us to resolve them. We are always happy to assist you.
Document Description
1. Chapter 05 Lecture and Animation Outline Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. To run the animations you must…
Document Share
Documents Related
Document Transcript
  • 1. Chapter 05 Lecture and Animation Outline Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. To run the animations you must be in Slideshow View. Use the buttons on the animation to play, pause, and turn audio/text on or off. Please Note: Once you have used any of the animation functions (such as Play or Pause), you must first click on the slide’s background before you can advance to the next slide.
  • 2. Membranes Chapter 5 2
  • 3. 3 Membrane Structure • Phospholipids arranged in a bilayer • Globular proteins inserted in the lipid bilayer • Fluid mosaic model – mosaic of proteins floats in or on the fluid lipid bilayer like boats on a pond
  • 4. 4 PolarHydrophilicHeadsNonpolarHydrophobicTails CH2 CH2 N+ (CH3)3 O P O O–O CH2H2C C O O O OC C CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH CH2 CH CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH3 CH3 H b. Space-filling modela. Formula c. Iconb. Space-filling modela. Formula c. Icon Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
  • 5. 5 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Glycoprotein Extracellular matrix protein Glycolipid Cholesterol Glycoprotein Integral proteins Actin filaments of cytoskeleton Intermediate filaments of cytoskeleton Peripheral protein Peripheral protein Glycolipid Cholesterol Glycoprotein Integral proteins Actin filaments of cytoskeleton Intermediate filaments of cytoskeleton
  • 6. 6 • Cellular membranes have 4 components 1. Phospholipid bilayer • Flexible matrix, barrier to permeability 1. Transmembrane proteins • Integral membrane proteins 1. Interior protein network • Peripheral or Intracellular membrane proteins 1. Cell surface markers • Glycoproteins and glycolipids
  • 7. 7 • Both transmission electron microscope (TEM) and scanning (SEM) used to study membranes • One method to embed specimen in epoxy – 1µm shavings – TEM shows layers Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Plasma membrane of cell 1 Plasma membrane of cell 2 Cell 1 Cell 2 25 nm © Dr. Donald Fawcett/ Photo Researchers, Inc.
  • 8. • Freeze-fracture visualizes inside of membrane 8 Knife Cell Medium 2. The cell often fractures through the interior, hydrophobic area of the lipid bilayer, splitting the plasma membrane into two layers. 3. The plasma membrane separates such that proteins and other embedded membrane structures remain within one or the other layers of the membrane. 4. The exposed membrane is coated with platinum, which forms a replica of the membrane. The underlying membrane is dissolved away, and the replica is then viewed with electron microscopy . Fractured upper half of lipid bilayer Exposed lower half of lipid bilayer Exposed lower half of lipid bilayer External surface of plasma membrane 0.15 µm 1. A cell frozen in medium is cracked with a knife blade. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. © Dr. Donald Fawcett/Visuals Unlimited
  • 9. 9 Phospholipids • Structure consists of – Glycerol – a 3-carbon polyalcohol – 2 fatty acids attached to the glycerol • Nonpolar and hydrophobic (“water-fearing”) – Phosphate group attached to the glycerol • Polar and hydrophilic (“water-loving”) • Spontaneously forms a bilayer – Fatty acids are on the inside – Phosphate groups are on both surfaces
  • 10. 10 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Plasma membrane of cell 1 Cell 1 Cell 2 Polar hydrophilic heads Polar hydrophilic heads Extracellular fluid Intracellular fluid (cytosol) Nonpolar hydrophobic tails
  • 11. • Bilayers are fluid • Hydrogen bonding of water holds the 2 layers together • Individual phospholipids and unanchored proteins can move through the membrane 11 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Mouse cell Fuse cells Intermixed membrane proteins Allow time for mixing to occur Human cell
  • 12. • Environmental influences on fluidity – Saturated fatty acids make the membrane less fluid than unsaturated fatty acids • “Kinks” introduced by the double bonds keep them from packing tightly • Most membranes also contain sterols such as cholesterol, which can either increase or decrease membrane fluidity, depending on the temperature – Warm temperatures make the membrane more fluid than cold temperatures • Cold tolerance in bacteria due to fatty acid desaturases 12
  • 13. 13 Membrane Proteins • Various functions: 1. Transporters 2. Enzymes 3. Cell-surface receptors 4. Cell-surface identity markers 5. Cell-to-cell adhesion proteins 6. Attachments to the cytoskeleton
  • 14. 14 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Enzyme Cell surface receptor Cell surface identity marker Cell-to-cell adhesion Attachment to the cytoskeleton Outside cell Inside cell Transporter
  • 15. 15 Structure relates to function • Diverse functions arise from the diverse structures of membrane proteins • Have common structural features related to their role as membrane proteins • Peripheral proteins – Anchoring molecules attach membrane protein to surface
  • 16. • Anchoring molecules are modified lipids with 1. Nonpolar regions that insert into the internal portion of the lipid bilayer 2. Chemical bonding domains that link directly to proteins 16 Protein anchored to phospholipid Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
  • 17. 17 • Integral membrane proteins – Span the lipid bilayer (transmembrane proteins) • Nonpolar regions of the protein are embedded in the interior of the bilayer • Polar regions of the protein protrude from both sides of the bilayer – Transmembrane domain • Spans the lipid bilayer • Hydrophobic amino acids arranged in α helices Membrane Proteins
  • 18. • Proteins need only a single transmembrane domain to be anchored in the membrane, but they often have more than one such domain 18 a. b. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Single transmembrane domain Many transmembrane domains
  • 19. 19 • Pores – Extensive nonpolar regions within a transmembrane protein can create a pore through the membrane – Cylinder of β sheets in the protein secondary structure called a β-barrel • Interior is polar and allows water and small polar molecules to pass through the membrane
  • 20. 20 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. β-pleated sheets
  • 21. 21 Passive Transport • Passive transport is movement of molecules through the membrane in which – No energy is required – Molecules move in response to a concentration gradient • Diffusion is movement of molecules from high concentration to low concentration – Will continue until the concentration is the same in all regions
  • 22. 22 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. a. b. c. d.
  • 23. 23 • Major barrier to crossing a biological membrane is the hydrophobic interior that repels polar molecules but not nonpolar molecules – Nonpolar molecules will move until the concentration is equal on both sides – Limited permeability to small polar molecules – Very limited permeability to larger polar molecules and ions
  • 24. • Facilitated diffusion – Molecules that cannot cross membrane easily may move through proteins – Move from higher to lower concentration – Channel proteins • Hydrophilic channel when open – Carrier proteins • Bind specifically to molecules they assist • Membrane is selectively permeable 24
  • 25. 25 Channel proteins • Ion channels – Allow the passage of ions – Gated channels – open or close in response to stimulus (chemical or electrical) – 3 conditions determine direction • Relative concentration on either side of membrane • Voltage differences across membrane • Gated channels – channel open or closed
  • 26. 26 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Extracellular fluid Extracellular fluid Cytoplasm a. Cytoplasm
  • 27. 27 Carrier proteins • Can help transport both ions and other solutes, such as some sugars and amino acids • Requires a concentration difference across the membrane • Must bind to the molecule they transport – Saturation – rate of transport limited by number of transporters
  • 28. 28 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. b. Extracellular fluid Cytoplasm
  • 29. 29 Osmosis • Cytoplasm of the cell is an aqueous solution – Water is solvent – Dissolved substances are solutes • Osmosis – net diffusion of water across a membrane toward a higher solute concentration
  • 30. 30 Urea molecule Semipermeable membrane Water molecules Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
  • 31. 31 Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer.
  • 32. 32 Osmotic concentration • When 2 solutions have different osmotic concentrations – Hypertonic solution has a higher solute concentration – Hypotonic solution has a lower solute concentration • When two solutions have the same osmotic concentration, the solutions are isotonic • Aquaporins facilitate osmosis
  • 33. Osmotic pressure • Force needed to stop osmotic flow • Cell in a hypotonic solution gains water causing cell to swell – creates pressure • If membrane strong enough, cell reaches counterbalance of osmotic pressure driving water in with hydrostatic pressure driving water out – Cell wall of prokaryotes, fungi, plants, protists • If membrane is not strong, may burst – Animal cells must be in isotonic environments 33
  • 34. 34 HumanRedBloodCellsPlantCells Shriveled cells Normal cells Flaccid cell Normal turgid cell Hypertonic Solution Isotonic Solution Hypotonic Solution Cells swell and eventually burst Cell body shrinks from cell wall © David M.Phillips/Visuals Unlimited Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 5 µm 5 µm 5 µm
  • 35. 35 Maintaining osmotic balance • Some cells use extrusion in which water is ejected through contractile vacuoles • Isosmotic regulation involves keeping cells isotonic with their environment – Marine organisms adjust internal concentration to match sea water – Terrestrial animals circulate isotonic fluid • Plant cells use turgor pressure to push the cell membrane against the cell wall and keep the cell rigid
  • 36. 36 Active Transport • Requires energy – ATP is used directly or indirectly to fuel active transport • Moves substances from low to high concentration • Requires the use of highly selective carrier proteins
  • 37. 37 • Carrier proteins used in active transport include – Uniporters – move one molecule at a time – Symporters – move two molecules in the same direction – Antiporters – move two molecules in opposite directions – Terms can also be used to describe facilitated diffusion carriers
  • 38. 38 Sodium–potassium (Na+ –K+ ) pump • Direct use of ATP for active transport • Uses an antiporter to move 3 Na+ out of the cell and 2 K+ into the cell – Against their concentration gradient • ATP energy is used to change the conformation of the carrier protein • Affinity of the carrier protein for either Na+ or K+ changes so the ions can be carried across the membrane
  • 39. 39 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Na+ K+ 6. Dephosphorylation of protein triggers change back to original conformation, with low affinity for K+ . K+ diffuses into the cell, and the cycle repeats. 1. Carrier in membrane binds intracellular sodium. 2. ATP phosphorylates protein with bound sodium. 5. Binding of potassium causes dephosphorylation of protein. 4. This conformation has higher affinity for K+ . Extracellular potassium binds to exposed sites. 3. Phosphorylation causes conformational change in protein, reducing its affinity for Na+ . The Na+ then diffuses out. P P P P P ATP + ADP Extracellular Intracellular
  • 40. 40 Coupled transport • Uses ATP indirectly • Uses the energy released when a molecule moves by diffusion to supply energy to active transport of a different molecule • Symporter is used • Glucose–Na+ symporter captures the energy from Na+ diffusion to move glucose against a concentration gradient
  • 41. 41 Na+ / K+ pump Na+ Glucose K+ Outside of cell ATP ADP + Pi Inside of cell Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Coupled transport protein
  • 42. Bulk Transport • Endocytosis – Movement of substances into the cell – Phagocytosis – cell takes in particulate matter – Pinocytosis – cell takes in only fluid – Receptor-mediated endocytosis – specific molecules are taken in after they bind to a receptor • Exocytosis – Movement of substances out of cell – Requires energy 42
  • 43. 43 Cytoplasm Cytoplasm 0.1 µm 1 µm Solute Bacterial cells Plasma membrane a. Phagocytosis Plasma membrane b. Pinocytosis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. a: © CDC/Dr. Edwin P. Ewing, Jr. b: © BCC Microimaging, Inc.Reproduced with permission
  • 44. • In the human genetic disease familial hypercholesterolemia, the LDL receptors lack tails, so they are never fastened in the clathrin- coated pits and as a result, do not trigger vesicle formation. The cholesterol stays in the bloodstream of affected individuals, accumulating as plaques inside arteries and leading to heart attacks. 44 Receptor protein Coated pit Clathrin Coated vesicle 90 nm Target molecule c. Receptor-mediated endocytosis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. (both): © Reproduced with permission from M.M. Perry and A.B. Gilbert, “Yolk transport in the ovarian follicle of the hen (Gallus domesticus): lipoprotein-like particles at the periphery of the oocyte in the rapid growth phase,” Journal of Cell Science, 39:257-72, October 1979. © The Company of Biologists
  • 45. • Exocytosis – Discharge of materials out of the cell – Used in plants to export cell wall material – Used in animals to secrete hormones, neurotransmitters, digestive enzymes 45 a. b. Plasma membrane Secretory vesicle Secretory product Cytoplasm 70 nm Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. b: © Dr. Brigit Satir
  • We Need Your Support
    Thank you for visiting our website and your interest in our free products and services. We are nonprofit website to share and download documents. To the running of this website, we need your help to support us.

    Thanks to everyone for your continued support.

    No, Thanks
    SAVE OUR EARTH

    We need your sign to support Project to invent "SMART AND CONTROLLABLE REFLECTIVE BALLOONS" to cover the Sun and Save Our Earth.

    More details...

    Sign Now!

    We are very appreciated for your Prompt Action!

    x