Membranes pt. 1

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Membranes pt. 1
2013-09-20 13:52:46
Cell Bio

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  1. No membrane =
    no cell
  2. Every cell has one __. 
    The first one we figured out existed in the __. 
    1850s: people realized that __.
    • cell membrane (plasma membrane)
    • mid 1800s 
    • something had been surrounding cell 
    • --> definite boundary
  3. Plasma Membrane
    - role: 
    - other __ are bounded by membranes adn act as __.
    • interaction with environment
    • internal structures
    • boundary to separate mixing between environments
  4. Membranes do what? 
    Diversity has to do with what?
    • compartmentalize (prevent mixing between cytoplasm and environment)
    • with the composition of membranes
    • (phospholipids, steroids, carbs, proteins)
  5. Evidence
    1) __ are easier to work with than proteins
  6. People: 
    Overton (year)
    - interest
    - theory
    - discovery
    - conclusion
    • 1890s
    • doctorate in botany; interested in what's around the cell
    • theory: whatever was in the boundary of the cell would affect what goes in and the rate 
    • found that lipid-soluble molecuels moved into cell much more rapidly compared to polar, insoluble substances
    • some ort of lipid was on surace
  7. People: 
    Hober and Frick
    - were they working together?
    - year
    - interest
    - suggested
    • Hober: 1910
    • Fricke: 1925
    • interest: RBC; interested in electrical resistance/ conductivity of cell; if you measure cell resistance, will contents of cell be resistant or attracted (it would conduct because of hte charge of the many particles,)
    • they found that in intact cells, resistance was high; conductivity was low
    • suggested it was due to lipids
  8. People also thought __ were on the surface, but they are __.
    • proteins
    • polar and highly conducting
  9. Experiments measuring __ supported the __idea.
    • conductivity
    • lipid
  10. People: 
    Harvey and Collander
    - year
    - working together? 
    - worked with?
    - interested in?
    - found what?
    • Harvey: 1912
    • Collander: 1927
    • not working together
    • worked with artificially prepared protein membrane
    • interested in movement through the membrane
    • found htat the membrane wsn't as permeable as what was on the surface of the cell
    • supported lipid idea
    • whatever was on surface wasn't just protein
  11. Unknown experiment with amoeba
    put drop of lipid on lside next to surface of amoeba cell--> began to spread out on the surface after sticking to cell
  12. Langmuir
    - year
    - career
    - interest?
    - studied?
    - what he did?
    • late 1915-1920
    • physical chemist
    • interested in monolayers and phospholipids
    • studied behavior of phospholipids
    • designed Langmuir trough to study lipids
    • mix lipids in benzene: as benzene evaporated, lipids would spread self over surface--> arranged self in monolayer
    • - measure SA with that
  13. In the mid-1920s, people were trying to figure out what?
    if lipids were on cells and if so, how many layers
  14. Gorter and Grendel
    - year
    - used
    • 1925
    • used mammal RBCs since they are hollow--> made RBC ghosts (all you see are the plasma membranes/ made by putting it in hypertonic solution
    • took RBCs, extracted lipid, put it in a trough, squeezed it, and measured SA of lipid and RBC and compared
  15. What did GOrter and Grendel discover?
    • phospholipd: RBC= 2:1
    • 0 used acetone, which only takes 2/3 of phospholipids
    • - used dry preparations, which caused lower yield due to shrinking
  16. Schmitt 
    - year
    - worked with
    - suggested?
    • mid 1930s
    • RBC ghosts, looking with polarized light (all wavelengths in same direction)
    • suggested lipid molecules are all perpendicular to the plane of the membrane
  17. Harvey and Cole
    - year
    - working together?
    - studied
    • 1931
    • yes
    • studied surface tension of cell, where it meets water
  18. Harvey And Cole studied cells, but what specifics about the cells?
    What else was measured?
    • kind of measurements for cells for about 0.2 dyne/cm (measure of surface area)
    • oil was also measured (10-15 dynes per cm)
  19. What did the measurements taken by Harvey and Cole say? What supports this?
    • told us that membrane can't just be lipid
    • cause if it were, the surface tension value would be similar to oil
  20. What did Harvey and Cole do when discovering that the membrane couldn't be just liquid?
    What did this support?
    • they added protein which brought the value near 0.2 dynes per cm
    • the idea that proteins had to be involved in lipids
  21. By early 1930s, what did we know about enzymes?
    • alot
    • proteins
    • specific
    • can work on things
    • molecules similar in structure won't get through as easily as other molecules (which suggested presence of proteins)
  22. Why didn't people just do a chemical analysis of membranes?
    • they did but there were serious problems:
    • - how do you know you're not dealing with more than the membrane?
  23. Four problems with membrane studying? 
  24. Four problems with membrane studying? 
    membranes of different speicies and types of cells leads to different results and questioning of results
  25. Four problems with membrane studying? 
    even if working with the same types of cells fromt eh same organism, the fact that they may have been in a different environment could have changed the results
  26. Four problems with membrane studying? 
    batch of cells from same environment, but different preparation--> different results
  27. Majority of studies done with __.
    animal membranes
  28. WHat else varies?
    lipid composition