Biological membranes Flashcards
CSM roles
-separates cell components from the outside of the cell
-transport substances in and out of the cell
-contains enzymes
-cell signalling -> releases chemicals and contains receptors
-the site of some chemical reactions
why is the fluid mosaic model used to show the phospholipid bilayer?
-phospholipids move like they are in a fluid
-looks like a mosaic due to the proteins scattered through the layer
glycoproteins
-made up of proteins and sugar molecule (molecules that consist of a carbohydrate plus a protein)
—recognition sites
—antigens
glycolipids
-made up of lipids and sugar molecule (molecules that consist of carbohydrates plus a lipid)
—similar to glycoproteins
—also stabilise membrane through H-bonds with water
phospholipid molecules
they have a ‘head’ which is hydrophilic and a ‘tail’ which is hydrophobic
hydrophilic
attracts water (capable of interacting with water through H-bonding)
hydrophobic
tends to repel water (won’t interact with water through H-bonding)
intrinsic proteins
-proteins that pass through both layers
-channel or carrier proteins
extrinsic proteins
-on the surface on cell membrane
-can act as enzymes
(simple) diffusion
the random movement of particles from an area of high to low concentration through a partially-permeable membrane
where can simple diffusion occur and why?
in small molecules only e.g. oxygen, carbon dioxide and steroids, because they are all non-polar, and the steroid hormones are fat-soluble
facilitated diffusion
the transport of larger, polar, and water soluble molecules across the phospholipid bilayer with the help of channel proteins
how does oxygen diffuse across the bilayer?
with simple diffusion because it is a small, non-polar molecule
how does water diffuse across the bilayer?
with facilitated diffusion because it is a larger, polar molecule
how do steroid hormones diffuse across the bilayer?
with simple diffusion because it is fat-soluble
