Membranes Flashcards
Cell membrane
Made of a phosphoplipid bilayer,it’s polarity allows material in and out making it selectively permeable.
Amphiphilic phospholipids.
Phosphate group=very polar
Fatty acids= very non polar
Phosphate groups are polar because…
-4 electronegative O atoms
-One atom is prone to ionize
Glycerol?
Polar but not as polar as phosphate
Fatty acid tails
Hydrocarbon chains are very non polar.
Saturated:- less fluid bc less gaps
Unsaturated: more fluid bc more gaps.
Selectively permeable membrane
Allows only some substances to pass through. -> depends on the size and polarity of the substance.
Which molecules can very easily with no exception pass through?
Small nonpolar molecules: O2, CO2, N2
Which molecules can pass for the most but still struggle sometimes?
Small uncharged polar molecules: H20 , NH3, glycerol
Which molecules can harshly squeeze in?
Large uncharged polar molecules :glucose, sucrose
Which molecules can’t pass in general?
All Ions:K+,Na+,Cl-
What is cholesterol?
A steroid -lipid molecule that is mostly nonpolar. In animal cells it is embedded in cell membranes to stabilize the membrane under different conditions
What does the placement of cholesterol allow?
->hydrophilic OH to be exposed to water
-> Hydrocarbon rings and tail to be within the hydrophobic core of the membrane
How does cholesterol help?
Dampens the effects of temperature on the membrane.
Fluid-Mosaic model
Model to explain the structure of the cell membrane. By SG Singer+ GL Nicolson
What are the properties of a cell membrane according to the Fluid-Mosaic model?
-not rigid, but flowing or fluid
-have proteins embedded through the membrane
-have empty regions
