What happens at cell membranes L2 Flashcards
what is the fluid mosaic model
continually moving sea of fluid lipids that contains a mosaic of many different proteins
2 type of ways a protein is arranged in the bilayer
intrinsic and extrinsic
amphiphatic=
polar and non-polar parts
which part is polar
the phosphate “head”
which part is non-polar
two long fatty acids
what is the orientation of the bilayer
polar heads facing outwards and tails pointing towards each other
why are the phospholipids arranged in this way
most energetically favourable and stable structure
why is the interior of the lipid membrane fluid
most double bonds are unsaturated = more cis bonds–> less van der waals—> lower melting point —> increased fluidity
what is diffusion rare proportional to
concentration gradient and hydrophobicity
what is the rate limiting step in diffusion
crossing the hydrophobic portion of the membrane
what molecules can easily diffuse across (4)
hydrophobic molecules O2, CO2, N2, benzene
for which molecules can some diffuse and some not
small uncharged polar molecules H2O, urea, glycerol
which molecules can occasionally diffuse across but don’t tend to
large uncharged polar molecules
glucose, sucrose
what can not diffuse across (non-permeable)
ions
passive diffusion=
diffusion unaided by transport proteins, no energy expended, movement down conc gradient
