model of cell membranes Flashcards
what is the name of the cell membrane model
fluid - mosaic model
what are cell membranes mainly made of?
phospholipids and proteins
what part of membrane is hydrophobic
fatty acid tails
what part of membrane is hydrophilic
phosphate head
what can polar molecules interact with
other polar molecules such as water
what can phospholipids form
bilayers
which way does the inner layer of hydrophilic heads point
points towards the cell
interacts with the water in the cytoplasm
which way does the outer layer of hydrophilic heads point
outwards
interacts with water surrounding the cell
what does the phopshoplipid bit of the membrane allow?
lipid soluble molecules across but not water soluble molecules
defenition of the fluid mosaic model
proteins are studded through a phospholipid bilayer
movement of molecules within the bilayer is fluid
what are the 2 different types of proteins
intrinsic
extrinsic
what does intrinsic proteins span?
across both layers of the bilayer
what does extrinsic proteins span?
are on either surface of the bilayer
what does extrinsic proteins do?
provide structural support and form recognition sites by identifying cells and receptor sites for hormone attatchment
what does intrinsic proteins include
transport proteins
what do transport proteins do
uses active / passive transport to move molecules and ions across the cell membrane
whats the fluid bit of the fluid mosaic model
individual phospholipid mols can move within a layer relative to one another
whats the mosaic bit of the fluid mosaic model
proteins embedded in bilayer vary in shape and size and in their distribution among the phospholipids
what does plant and animal cell membranes contain
glycoproteins, glycolipids and sterols
what is the sterol in animal cell membranes
cholesterol
where does cholesterol occur
between phospholipid molecules
what does cholesterol do
makes membrane more stable at high temperatures and more fluid at low temps
what makes membrane more stable at high temperatures and more fluid at low temps in plant cells
sterols
what is the glycocalyx
carbohydrate layer around an animal cell
roles of glycocalyx
hormone recptors
cell to cell recognition
cell to cell adhesion
diffuseability of small molecules
move between phospholipid mols and diffuse across membrane
example of small molecules
oxygen and carbon dioxide
example of lipid soluble molecule
vitamin A
example of water soluble molecule
glucose
polar molecules
diffuseability of lipid soluble substances
dissolve in phospholipid and diffuse across membrane
why can lipid soluble substances move through cell membrane easier than water soluble substances
phospholipid layer is hydrophobic so lipid - soluble molecules move throuh the cell membrane easier
what can water soluble substances not diffuse through
phospholipids
what must water soluble substances pass through
intrinsic protein moleulces which form water filled channels across membrane
as a result of the intrinsic proteins what happens to cell surface membrane permability
selectively permable to water
