BIOLOGY 189Cell Membranes and     Signaling
Biological Membranes• General structure: fluid mosaic model.• Phospholipids form a bilayer• Two regions:   Hydrophilic re...
Membrane Molecular Structure
Biological Membranes • May differ in lipid composition as   there are many types of   phospholipids. • Phospholipids may d...
Biological Membranes• Two important factors in membrane  fluidity:  Lipid composition—types of fatty   acids can increase...
Biological Membranes• Membranes contain proteins  Peripheral membrane proteins   lack hydrophobic groups and   are not em...
Biological Membranes • Anchored membrane proteins   have lipid components that anchor   them in the bilayer. • Transmembra...
Biological Membranes• Plasma membrane carbohydrates  located on the outer membrane  serve as recognition sites.  Glycolip...
Selective Permeability • Biological membranes allow   some substances to pass or not.   Passive transport does not    req...
Diffusion        Passive transport • Two types of diffusion:   Simple diffusion   Facilitated diffusion through    chann...
Diffusion• Speed of diffusion depends on   Diameter of the molecules—smaller    molecules diffuse faster   Temperature o...
Diffusion  Higher concentration inside  the cell causes the solute to  diffuse out, and a higher  concentration outside  c...
Osmosis• Diffusion of water across  membranes.• Depends on the concentration of  solute molecules on either side of  the m...
Hypertonic, Isotonic, HypotonicWhen comparing two solutions separated by a membrane:• A hypertonic solution has a higher  ...
Hypotonic
Isotonic
Hypertonic
Hypotonic         Isotonic     Hypertonic            solution         solution      solution                   H2O     H2O...
Facilitated Diffusion Diffusion aided by • Channel proteins. Integral   membrane proteins that form   channels across the ...
A Ligand-Gated Channel Protein Opens in Response to a Stimulus
Diffusion• Water crosses membranes with the help  of Aquaporins (specific channels)• They allow large amounts of water to ...
Carrier Proteins Facilitate Diffusion
Active transport• requires energy to move substances  against their concentration gradients.• energy source: ATP.• A subst...
Active transport Two types • Primary active transport involves   hydrolysis of ATP for energy. • Secondary active transpor...
Active Transport • The sodium–potassium (Na+–K+)   pump is an integral membrane   protein that pumps Na+ out of a cell   a...
EXTRACELLULAR                       [Na+] high                                             Na+  FLUID                [K+] ...
Endocytosis and Exocytosis • Macromolecules are too large or   too charged to pass through   biological membranes and inst...
Endocytosis Three types: • Phagocytosis, (“cellular eating”) • Pinocytosis, (“cellular drinking”) • receptor mediated endo...
Endocytosis
Receptor-Mediated Endocytosis
Exocytosis Exocytosis moves materials out of the cell in vesicles.                         Summary of cell membrane       ...
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  • VIDEO 5.1 Cell Visualization: Membranes, hormones, and receptors
  • See Figure 5.1
  • Figure 7.13 The water balance of living cells
  • Figure 7.16, 1–6 The sodium-potassium pump: a specific case of active transport
  • Bio 189 cell_membranes_and_signaling_spr

    1. 1. BIOLOGY 189Cell Membranes and Signaling
    2. 2. Biological Membranes• General structure: fluid mosaic model.• Phospholipids form a bilayer• Two regions:  Hydrophilic regions—“heads” that associate with water molecules  Hydrophobic regions—nonpolar fatty acid “tails” that do not dissolve in water
    3. 3. Membrane Molecular Structure
    4. 4. Biological Membranes • May differ in lipid composition as there are many types of phospholipids. • Phospholipids may differ in: Fatty acid chain length Degree of saturation Kinds of polar groups present
    5. 5. Biological Membranes• Two important factors in membrane fluidity: Lipid composition—types of fatty acids can increase or decrease fluidity Temperature—membrane fluidity decreases in colder conditions
    6. 6. Biological Membranes• Membranes contain proteins Peripheral membrane proteins lack hydrophobic groups and are not embedded in the bilayer. Integral membrane proteins are partly embedded in the bilayer.
    7. 7. Biological Membranes • Anchored membrane proteins have lipid components that anchor them in the bilayer. • Transmembrane proteins extend through the bilayer on both sides
    8. 8. Biological Membranes• Plasma membrane carbohydrates located on the outer membrane serve as recognition sites. Glycolipid—a carbohydrate bonded to a ________ Glycoprotein—a carbohydrate bonded to a ______
    9. 9. Selective Permeability • Biological membranes allow some substances to pass or not. Passive transport does not require energy. Active transport requires energy.
    10. 10. Diffusion Passive transport • Two types of diffusion: Simple diffusion Facilitated diffusion through channel proteins or aided by carrier proteins
    11. 11. Diffusion• Speed of diffusion depends on  Diameter of the molecules—smaller molecules diffuse faster  Temperature of the solution—higher temperatures lead to faster diffusion  The concentration gradient the greater the concentration, the faster a substance will diffuse
    12. 12. Diffusion Higher concentration inside the cell causes the solute to diffuse out, and a higher concentration outside causes the solute to diffuse in, for many molecules.
    13. 13. Osmosis• Diffusion of water across membranes.• Depends on the concentration of solute molecules on either side of the membrane.• Water passes through special membrane channels.
    14. 14. Hypertonic, Isotonic, HypotonicWhen comparing two solutions separated by a membrane:• A hypertonic solution has a higher solute concentration• Isotonic solutions have equal solute concentrations• A hypotonic solution has a lower solute concentration
    15. 15. Hypotonic
    16. 16. Isotonic
    17. 17. Hypertonic
    18. 18. Hypotonic Isotonic Hypertonic solution solution solution H2O H2O H2O H2OAnimal cell Lysed Normal Shriveled H2O H2O H2O H2O Plant cell Turgid (normal) Flaccid Plasmolyzed Funny animation
    19. 19. Facilitated Diffusion Diffusion aided by • Channel proteins. Integral membrane proteins that form channels across the membrane. • Substances can also bind to carrier proteins to speed up diffusion.
    20. 20. A Ligand-Gated Channel Protein Opens in Response to a Stimulus
    21. 21. Diffusion• Water crosses membranes with the help of Aquaporins (specific channels)• They allow large amounts of water to move against its concentration gradient• I t may “hitchhike” with ions such as Na+ as they pass through channels.
    22. 22. Carrier Proteins Facilitate Diffusion
    23. 23. Active transport• requires energy to move substances against their concentration gradients.• energy source: ATP.• A substance moves in the direction of the cell’s needs, usually by means of a specific carrier protein.
    24. 24. Active transport Two types • Primary active transport involves hydrolysis of ATP for energy. • Secondary active transport uses the energy from an ion concentration gradient, or an electrical gradient.
    25. 25. Active Transport • The sodium–potassium (Na+–K+) pump is an integral membrane protein that pumps Na+ out of a cell and K+ in. • One molecule of ATP moves two K+ and three Na+ ions.
    26. 26. EXTRACELLULAR [Na+] high Na+ FLUID [K+] low Na+ Na+ Na+ Na+ Na+ Na+ Na+ [Na+] low ATP Na+ PCYTOPLASM [K+] high P ADP 1 2 3 K+ K+ K+ + K+ K P K+ P 6 5 4
    27. 27. Endocytosis and Exocytosis • Macromolecules are too large or too charged to pass through biological membranes and instead pass through vesicles. • Cells use endocytosis or exocytosis
    28. 28. Endocytosis Three types: • Phagocytosis, (“cellular eating”) • Pinocytosis, (“cellular drinking”) • receptor mediated endocytosis
    29. 29. Endocytosis
    30. 30. Receptor-Mediated Endocytosis
    31. 31. Exocytosis Exocytosis moves materials out of the cell in vesicles. Summary of cell membrane transport

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