Chapter 6 Flashcards
Phospholipid bilayer
Hydrophilic phospholipid head regions with hydrophobic tails; Intracellular environment; Extracellular environment
Transmembrane proteins(cross or anchor, embedded into membrane)
Form pores, channels; Anchor points for other things to attach
Interior protein network
- Peripheral protein
- “twizzlers” can tie into them
Cell surface markers
Anchors to extracellular matrix(ECM)
o Helps hold things in place, provides structure and stability
o Manipulated based on tissues it is supporting
o Two important things: important for immune system and how cells recognize each other!
Glycoprotein: has carbohydrate rings that form strings
Glycolipid: *if arrangement found, leaves alone; if arrangement not found, white blood cell will get rid of “invaders”
Imaging the plasma membrane
Both transmission electron microscope(TEM) and scanning(SEM) used to study membranes
o Not the microscopes in lab, not able to reach that level
* One method to embed specimen in epoxy
o 1 micrometer shavings(imagine meat slicer at the deli)
o TEM shows layers
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Freeze Fracture
- Take tissue with cells
- Use glorified deli slicer to separate layers
- Reveals fluid of mosaic model of plasma membranes
Disproving the fluid mosaic model
- If cut, will not be smooth like sandwich model, which was disproved
- As the name suggests, fluid moving layer(not a lot, but enough to bob around like a boat in a lake)
Ways to alter membrane fluidity:
o Increase amount of saturated fatty acids DECREASES fluidity
o Increase of cholesterol DECREASES fluidity
o Increase of temperature INCREASES fluidity
The many uses of membrane proteins
transporter, enzyme, cell surface receptor, cell surface identity marker, cell-to-cell adhesion, attachment to the cytoplasm
Passive diffusion
motion of molecules drives the spread
* Concentration gradients are followed
* No energy needed, just the random motion of molecules
* Small, uncharged molecules go through membrane
* Small, polar molecules may diffuse too, just more slowly
o Even though tails are hydrophobic, water is so small that it passes through easily
* Some things diffuse readily through a cell membrane
Facilitated diffusion
some molecules diffuse with “help” from a special carrier proteins; some things too big/too polar to go through plasma membrane
Has special protein channels that can work both ways; can open and close to one side or the other
protein channel facilitated motion of molecules across the membrane
No energy required; concentration gradients are followed, still a form of diffusion
Temporary ionic bond to go in one side and out the other
* Example: Glucose(charged stuff like ions)
Osmosis
- Semipermeable membrane: solutes stay in place, water diffuses through the membrane
o Water is polar, but is very small so it can sneak through
o Cells may also have special channels called aquaporins also assist water by moving it faster/in large amounts - Special case of diffusion
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Tonicity
- Hypotonic: low solute concentration
- Hypertonic: high solute concentration
- Isotonic: equivalent
- **Comparison with solution and cell environment; always discuss the extracellular solution relative to the intracellular environment!
Secondary Active Transport/Couple transport
- energy not directly consumed, but a concentration gradient is need to drive it!
- One molecule moves down concentration gradient, other moves against
- Co vs. Counter-transport
Permeability
o Small, uncharged polar molecules
Need a bit of help, not tons, just a bit
o Large uncharged polar molecules
Facilitated diffusion
o Small ions
Facilitated diffusion (or active transport?)
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