2.5 biological membranes Flashcards
state the role of membranes
partially permeable barriers between the cell and its environment, between organelles and
the cytoplasm and within organelles
sites of chemical reactions
sites of cell communication (receptors, cell signalling, cell reconition).
what is the fluid mosaic model
model that shows arrangement of biological membranes
name the components in the fluid mosaic model
phospholipid
intrinsic proteins(carrier,channel)
extrinsic proteins
glycoproteins
glycolipids
cholesterol
what is a micelle
one layer of phospholipids, creates sphere shape
whats a bilayer
two layers of phospholipids
describe channel proteins
have pores that act as channels to allow ions to pass through
describe carrier proteins
change shape using ATP to carry specific molecules across membrane
describe extrinsic proteins
found on the surface
provides mechanical support and act as cell receptors for hormones etc.
describe glycolipids
carbohydrate chain attached to phosholipid
role in cell recognition and act as cell markers or antigens
describe glycoproteins
carbohydrate chain attached to protein molecule
receptors for chemical signals/hormones/toxins
role in cell adhesion
describe cholesterol
4 carbon based rings in fatty acid tail layer
provides mechanical stability and flexibility
restricts movement of membrane etc
how does cholesterol affect membrane permeability
buffers the effect of lower temperature by preventing phospholipids getting too close = prevents reduction in fluidity
what is simple diffusion
the net movement of particles down a concentration gradient from an area of higher conc. to lower conc.
what molecules does simple diffusion allow to cross membranes
small polar or non polar
what is facilitated diffusion
diffusion using proteins (carrier or channel)