4.3 membrane structure. membrane function surrounds all cells regulates cell’s internal...
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4.3 Membrane Structure4.3 Membrane Structure
Membrane FunctionMembrane FunctionSurrounds all cellsRegulates cell’s internal
environment◦Maintains HOMEOSTASIS
Maintains the same conditions constant inside the cell, regardless of external conditions
Membrane FunctionMembrane FunctionRegulates what enters and exits
the cells◦Selectively permeable
Only allows specific materials to pass over the membrane
Examples: spaghetti strainer & mosquito netting
Allows water & nutrients to enter the cell and wastes to leave the cell
Membrane Structure:Membrane Structure:1. Phospholipids1. PhospholipidsPhospholipid
◦Lipid with… 2 fatty acids 1 glycerol 1 phosphate group 1 polar group
◦Fatty acids are hydrophobic◦The rest of the phospholipid is hydrophilic
Membrane StructureMembrane Structure1. Phospholipids1. PhospholipidsForm a bilayer
◦Cell membrane has two layers of phospholipids
◦Polar “heads” attracted to water, carbs, proteins outside the cell and in the cytoplasm Face outward
◦Non-polar “tails” not attracted to water
Face inward
Membrane StructureMembrane Structure2. Cholesterol2. CholesterolLipid
◦Hydrophobic Fits in with fatty acid tails of
phospholipids
Function:◦Keeps membrane from freezing or
falling apart◦Helps “stabilize” membrane
Membrane StructureMembrane Structure3. Membrane Proteins3. Membrane ProteinsMembrane proteins have:
◦Hydrophobic regions & Hydrophilic regions
◦These help membrane proteins STAY in membrane
Membrane StructureMembrane Structure3. Membrane Proteins3. Membrane ProteinsWhich color of the protein is
hydrophilic? Hydrophobic?
Membrane StructureMembrane Structure3. Membrane Proteins3. Membrane ProteinsFunction:
◦Recognize material & transport into or out of cell
Fluid Mosaic ModelFluid Mosaic ModelDescribes the cell membrane:
◦Phospholipids are always moving like a fluid membrane proteins make a pattern in the cell membrane
REMEMBER THIS…?REMEMBER THIS…?What is concentration?
◦The amount of particles in a particular area
Concentration gradientConcentration gradientConcentration gradient:
unequal distribution of particles (solute) in a solution
Particles will move until the concentration is equal◦Dynamic equilibrium
Concentration GradientConcentration GradientWhat will happen?
Concentration Concentration Dynamic equilibrium!
Bozeman membraneBozeman membranehttp://www.youtube.com/watch?v
=y31DlJ6uGgE