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THE CELL MEMBRANE - structure and function overview

Details of the cell membrane, and movement of materials across the membrane.

Richard Mollee

on 15 February 2011

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Transcript of THE CELL MEMBRANE - structure and function overview

I.The Plasma Membrane
A.Make up
1.Phospholipid bilayer, protein and carbohydrates
B.The Fluid Mosaic Model
a.Phospholipid layers are not locked together.
i. they are amphipathic
-both hydrophobic and hydrophillic ends
-membrane is held together by these interactions!
b.fluidity is needed for proper function
2.Mosaic nature
a collage of different molecules
i.Proteins – determine function
-integral, within bilipid layer
-peripheral, loosely bound to surface of the bilipid layer.
C. Function of the membrane
1.cell to cell recognition (ECM = extra-cellular matrix)
a. cells recognize one another by identifying the carbo’s on the membrane
i. important in immuno reaction
-determine the nature of the cell
glycoproteins 2. Membrane proteins
a. transportation
i. channel for a specific solute
ii. active pumps
b. Enzymatic activity
i. membrane proteins can be enzymes
ii. pathways in sequence.
c. Signal transduction
i. reception of outside signals
d. intercellular joining
i. binding cells together
e. bonding site
i. intracellular materials like cytoskeleton
ii. Extra Cellular Matrix
3. Semipermiability
a.Passive Transport - no energy
i. membrane slows ions and large polar molecules
ii.Hydrophobic molecules and small molecules like water pass with ease,
iii. Diffusion
-Substances move from where they are highly concentrated
to where there is a lower concentration.
-concentration gradient!!
- diffusion of water across a membrane
- three situations possible
Isotonic – same
Dynamic equilibrium
Hypertonic – ECF is high conc
Water moves out
Hypotonic – ECF is low conc
Water moves in
v. Osmoregulation
- cell without walls
low tolerance for water change
will shrivel in hypertonic
will explode in hypotonic
called being lysed
adaptations for this incl.
Contractile vacuole
- cells with walls
wall prevents drastic changes
hyper. - becomes plasmolysed
hypo. – becomes turgid
iso. – becomes flacid, or limp
vi. Facilitated Diffusion
- movement of substances from high conc. to low conc.
with the help of transport proteins
b. Active transport – requires energy!
i.ATP is used
ii.movement of molecules against the concentration gradient.
iii.Also done by transport proteins
-the Na – K pump
-against steep conc gradients
Cell spitting
Common in secretory cells
-Endocytosis – opposite of exo.
Three types
Phagocytosis – solids
Pinocytosis – liquids
Receptor mediated endo.
--> Aquire bulk quantities of a specific substance http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_the_sodium_potassium_pump_works.html http://www.teachersdomain.org/asset/tdc02_int_membraneweb/ http://entochem.tamu.edu/G-Protein/index.html signal transduction http://www.yellowtang.org/animations/bilayer.swf http://www.yellowtang.org/animations/membrane_proteins_v2.swf http://www.yellowtang.org/animations/biochemical_pathway.swf biochem pathway just passing through http://www.yellowtang.org/animations/diffusion.swf diffusion http://www.yellowtang.org/animations/diffusion3.swf diffusion 2 http://www.yellowtang.org/animations/facDiffusion.swf facilitated diffusion http://www.yellowtang.org/animations/protonPump.swf proton pump 1 proton pump 2 http://www.yellowtang.org/animations/active_transport.swf active transport http://www.yellowtang.org/animations/passive_transport_v2.swf facilitated diff of glucose http://www.yellowtang.org/animations/cotransport1.swf symport and antiport http://www.yellowtang.org/animations/endocytosis_exocytosis.swf endocytosis exocytosis THE PLASMA MEMBRANE
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