Chapter 6- Lipids, Membranes, and the First cells
Cell membrane or Plasma membrane: layer of molecules that surround the cell
Bagham used transmission electron microscopes to produce images of lipids called micrographs in
lipids: non-polars and hydrophobic
-not a monomer nor polymer
-four ring structure (polar) and isoprene chain (non-polar)
-glycerol,phosphate group, and 2 fatty acid chains
-phospholipids containing isoprene are found in archaea
-compunds that countain hydrophobic and hydrophilic regions are known as amphipathic.
lipid bilayers: two sheets of phospholipid molecules allign
micelles: when the hydrophobic tails face inwards and the heads are outwards
Permeability: the tendency to allow a given substance to pass across a a membrane.
Selective permeability: some molecules can pass more easily across the membrane than other
(small, non-polar molecules move across the bilayers quickly)
-The smaller the carbon chain and the more double bonds (unsaturated), means the more permeable
the membrane is. Affect of temperature on permeability
-fluidity decreases with temperature
-low temperatures cause fats to solidify.
-dissolved molecules and ions are known as solutes
-solutes tend to move from high concentration to a low concentration. This creates a concentration
-osmosis is the movement of water in diffusion
-osmosis occurs only in selectively permeable membrane
-in osmosis, water moves towards the side with the higher solute concentration, evening out the density
-this is important because it can swell or shrink a membrane-mound vessicle
Hypertonic: water moves to outside and cell shrinks
Hypotonic: water moves to inside and cell swells
when both concentrations are equal is is called isotonic
-In 1935 Hugh and James Danielli proposed that plasma membranes were structured like sandwhiches
(polar outside, non-polar inside)
-In 1972, Singer and Nicolson suggested that membrane proteins are amphipathic and the over
structure was fluid and dynamic.
-they are amphipathic due t