Chapter 3:   Cells:  The Living Units
The Cellular Basis of Life:  Cell Theory <ul><li>A cell is the basic structural & functional unit of living organisms </li...
Cell Diversity
The Composite Cell
The Plasma Membrane:  Structure <ul><li>Very thin, s electively  permeable phospholipid bilayer </li></ul><ul><li>Membrane...
 
The Plasma Membrane:  Functions <ul><li>Defines the cell’s boundary </li></ul><ul><li>Selectively permeable membrane that ...
Transport: Protein channels and pumps transport specific substances into the cell  Enzymatic Activity: Some enzymes are at...
Intercellular Joining: Cell adhesion molecules (CAMS) provide binding sites for cell-cell interactions Cell-Cell Recogniti...
Plasma Membrane Special Structures
Special Structures:  Tight Junctions <ul><li>Interlocking junctional proteins fused together to form a relatively impermea...
Special Structures:  Desmosomes <ul><li>Plaque & linker proteins interdigitate like a zipper </li></ul><ul><li>Allow for c...
Special Structures:  Gap Junctions <ul><li>Communicating junction between cells </li></ul><ul><li>Connexons are transmembr...
Membrane Transport <ul><li>Cells are surrounded by extracellular fluid/ interstitial fluid containing nutrients, amino aci...
Membrane Transport <ul><li>Passive Processes </li></ul><ul><ul><li>Diffusion </li></ul></ul><ul><ul><ul><li>Simple Diffusi...
Diffusion <ul><li>The tendency of molecules or ions to scatter evenly throughout the environment </li></ul><ul><li>Molecul...
Diffusion <ul><li>Molecules diffuse through the membrane if: </li></ul><ul><li>Lipid-soluble </li></ul><ul><li>Small </li>...
Simple Diffusion  <ul><li>Small, non-polar, lipid-soluble substances diffuse directly through the lipid bilayer from regio...
Channel-Mediated Facilitated Diffusion  <ul><li>Protein channels form “tunnels” that allow small, lipid-insoluble molecule...
Carrier-Mediated Facilitated Diffusion  <ul><li>Large, polar, lipid-insoluble molecules such as sugars and amino acids bin...
Osmosis  <ul><li>Specific to the movement of  water  (a solvent) through a membrane from regions of  high water concentrat...
Diffusion –vs- Osmosis
Tonicity  Hypertonic:  Osmotic pressure outside the cell is higher, water  leaves  cell faster than it enters Isotonic:  O...
Filtration  <ul><li>Movement of molecules through membranes from regions of  high hydrostatic pressure  to regions of  low...
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Chapter3a

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Spring 2010 chapter 3a PowerPoint for BIOL2401 (Human Anatomy & Physiology) at San Antonio College with Alba

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Chapter3a

  1. 1. Chapter 3: Cells: The Living Units
  2. 2. The Cellular Basis of Life: Cell Theory <ul><li>A cell is the basic structural & functional unit of living organisms </li></ul><ul><li>The activity of an organism depends both the individual & collective activity of its cells </li></ul><ul><li>Biochemical activities of cells are dictated by the relative number of their specific subcellular structures </li></ul><ul><li>Continuity of life has a cellular basis </li></ul>
  3. 3. Cell Diversity
  4. 4. The Composite Cell
  5. 5. The Plasma Membrane: Structure <ul><li>Very thin, s electively permeable phospholipid bilayer </li></ul><ul><li>Membrane proteins: surface receptors, pumps, channels, cytoskeletal anchors </li></ul><ul><li>Membrane carbohydrates- Cell recognition, “ID tags” </li></ul>
  6. 7. The Plasma Membrane: Functions <ul><li>Defines the cell’s boundary </li></ul><ul><li>Selectively permeable membrane that transports substances in and out of the cell </li></ul><ul><li>Generates and maintains the resting membrane potential </li></ul><ul><li>Mediates cell-cell and cell-environment interactions </li></ul>
  7. 8. Transport: Protein channels and pumps transport specific substances into the cell Enzymatic Activity: Some enzymes are at the membrane, supplying products where they are needed Signal Transduction: Some membrane proteins are receptors that receive external signals and initiate cascades of chemical reactions
  8. 9. Intercellular Joining: Cell adhesion molecules (CAMS) provide binding sites for cell-cell interactions Cell-Cell Recognition: Some glycoproteins serve as cellular “ID” tags that allow cells to recognize each other Attachment to the cytoskeleton and ECM: Some membrane proteins act as anchors for the cell, binding the cell to its environment and supporting the cytoskeleton
  9. 10. Plasma Membrane Special Structures
  10. 11. Special Structures: Tight Junctions <ul><li>Interlocking junctional proteins fused together to form a relatively impermeable barrier around cells </li></ul><ul><li>Prevents molecules from passing between adjacent cells </li></ul><ul><li>Example: Digestive tract lining to prevent “seeping” </li></ul>
  11. 12. Special Structures: Desmosomes <ul><li>Plaque & linker proteins interdigitate like a zipper </li></ul><ul><li>Allow for cell sheets to form </li></ul><ul><li>Also prevents cell sheets subjected to mechanical stress from tearing </li></ul><ul><li>Examples: Skin, heart muscle </li></ul>
  12. 13. Special Structures: Gap Junctions <ul><li>Communicating junction between cells </li></ul><ul><li>Connexons are transmembrane proteins that form channels that span across adjacent cells </li></ul><ul><li>Essential for excitable tissue that require rapid communication in order to synchronize activities </li></ul><ul><li>Examples: Cardiac & smooth muscle </li></ul>
  13. 14. Membrane Transport <ul><li>Cells are surrounded by extracellular fluid/ interstitial fluid containing nutrients, amino acids, sugars, fatty acids, vitamins, etc. </li></ul><ul><li>Cells need to extract essential substances from interstitial fluid in order to survive </li></ul><ul><li>Traffic across the plasma membrane is constant but is also selective on what substances are introduced into the cell </li></ul><ul><li>Transport is either passive or active </li></ul>
  14. 15. Membrane Transport <ul><li>Passive Processes </li></ul><ul><ul><li>Diffusion </li></ul></ul><ul><ul><ul><li>Simple Diffusion </li></ul></ul></ul><ul><ul><ul><li>Facilitated Diffusion (channel & carrier-mediated) </li></ul></ul></ul><ul><ul><ul><li>Osmosis </li></ul></ul></ul><ul><ul><li>Filtration </li></ul></ul><ul><li>Active Processes </li></ul><ul><ul><li>Active Transport </li></ul></ul><ul><ul><li>Vesicular Transport </li></ul></ul>
  15. 16. Diffusion <ul><li>The tendency of molecules or ions to scatter evenly throughout the environment </li></ul><ul><li>Molecules and ions move down their concentration gradients until equilibrium is reached </li></ul><ul><li>[High]  [Low] </li></ul>
  16. 17. Diffusion <ul><li>Molecules diffuse through the membrane if: </li></ul><ul><li>Lipid-soluble </li></ul><ul><li>Small </li></ul><ul><li>Assisted by a carrier molecule </li></ul><ul><li>Types of Diffusion: </li></ul><ul><li>Simple Diffusion: Unassisted diffusion </li></ul><ul><li>Facilitated Diffusion: Assisted diffusion </li></ul><ul><ul><li>Channel-mediated </li></ul></ul><ul><ul><li>Carrier-mediated </li></ul></ul><ul><li>3) Osmosis: Diffusion of solvents (water) </li></ul>
  17. 18. Simple Diffusion <ul><li>Small, non-polar, lipid-soluble substances diffuse directly through the lipid bilayer from regions of high concentration to low concentration </li></ul><ul><li>Examples: Oxygen, Carbon dioxide, fat-soluble vitamins </li></ul>
  18. 19. Channel-Mediated Facilitated Diffusion <ul><li>Protein channels form “tunnels” that allow small, lipid-insoluble molecules (water, ions) into the cell </li></ul><ul><li>Channels are selective, only allowing molecules of certain sizes and charges to pass through </li></ul>
  19. 20. Carrier-Mediated Facilitated Diffusion <ul><li>Large, polar, lipid-insoluble molecules such as sugars and amino acids bind to protein carriers and are “shuttled” across the membrane </li></ul><ul><li>Carrier membrane proteins are molecule-specific </li></ul>
  20. 21. Osmosis <ul><li>Specific to the movement of water (a solvent) through a membrane from regions of high water concentrations to regions of low water concentrations </li></ul><ul><li>Osmotic diffusion of water may be directly through the lipid bilayer or through aquaporins </li></ul>
  21. 22. Diffusion –vs- Osmosis
  22. 23. Tonicity Hypertonic: Osmotic pressure outside the cell is higher, water leaves cell faster than it enters Isotonic: Osmotic pressure in and out of cell are equal, water enters and leaves cell at same rate Hypotonic: Osmotic pressure inside cell the higher, water enters the cell faster than it leaves
  23. 24. Filtration <ul><li>Movement of molecules through membranes from regions of high hydrostatic pressure to regions of lower hydrostatic pressure </li></ul><ul><li>Separation of solids from fluids </li></ul><ul><li>Generally applies only to capillary walls </li></ul>

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