cellular membranes Flashcards
what is the role of the plasma membrane
act as a barrier between the cell and their environment
why are plasma membranes described as being partially permeable
some molecules can pass through but others cannot
what do plasma membranes allow
recognition of other cells and cell signalling
what is the role of membranes within cells
membranes around organelles divides the cell into its separate components
what can membranes within a cell form
vesicles
what are vesicles useful for
transporting substances around the cell
how is membranes within cells responsible for transcription
allows mRNA to leave nucleus via nuclear membrane
what can membranes within cells be the site of
reactions, eg inner membrane of mitochondria contains enzymes for respiration
what molecules is the cell membrane composed of
phospholipid bilayer
how does the fluid mosaic model describe the phospholipid bilayer
it is fluid as phospholipids are constantly moving as it is a mosaic as proteins are randomly arranged throughout
what lipid molecules are present within the bilayer and what is their role
cholesterol, impact fluidity
describe the phospholipid bilayer
heads of phospholipids and hydrophilic and the tails are hydrophobic
molecules arrange themselves into a bilayer with their heads facing outwards and tails facing inwards
what substances does the phospholipid bilayer not allow through
polar as the hydrophobic tails repels this and molecules that are too large as cannot fit between phospholipids
how does cholesterol work at high temperatures
pushes the phospholipids closer together to decrease fluidity
what do channel proteins do
allow charged/ large molecules to pass through via facilitated diffusion
what do carrier proteins do
allow molecules to pass via active transport
what do proteins on the outside of the bilayer act as
receptors for cell signalling
how do glycolipids and glycoproteins stabilise the membrane
form hydrogen bonds with water molecules surrounding
what sites do glycolipids and glycoproteins act as
receptors for cell signalling as well as allowing drugs, hormones and antibodies to bind
how are glycolipids and glycoproteins involved in the immune response
they are antigens
what is cell signalling
cellular communication
describe the 3 step process of cell signalling
- cell releases a messenger molecule (hormone)
- molecule travels to another cell (target cell/ organ)
- molecule binds to receptor
what are special about receptors
they are complementary and have specific shapes for messenger molecules
explain how glucagon works
binds to receptors on liver cells and triggers the break down of glycogen into glucose
what does cell damage cause the release of
histamine
how does histamine work
binds to receptors on the surface of other cells which causes inflammation
how do antihistamines work
they block histamine receptors
