2.4.1~ The structure of cell membranes Flashcards
what does the cell surface membrane create
an enclosed space separating the internal cell environment from the external environment
what does the cell surface membrane create inside the cell
intracellular membranes form compartments within the cell such as the nucleus, mitochondria and RER
how do membranes act as an interface for communication
-they are partially permeable
-substances can cross the membranes by diffusion, osmosis and active transport
what is the bilayer in cellular membranes formed from
phospholipids
how wide is phospholipd bilayer
roughly 7nm
what can the phospholipid bilayer be seen under
an electron microscope at very high magnifications
when was the fluid mosaic model first outlined
1972
what does fluid mosaic model do
explains how biological molecules are arranged to form cell membranes
what can the fluid mosaic model help to explain
-passive and active movement between cells and their surroundings
-cell-to-cell interactions
-cell signaling
what 2 distinct regions do phospholipds contain
-a polar head (hydrophillic) which is soluble in water
-a non-polar tale (hydrophobic) which is insoluble in water
how is the phospholipd monolayer arranged
a single layer with the hydropillic phosphate heads in the water and hydrophobic tails sticking up away from the water
what happens if phospholipds are mixed/shaken with water (micelle)
they from spheres with the hydrophilic phosphate heads facing out towards the water and the hydrophobic fatty acid tails facing towards each other–> this is called a micelle
what happens if phospholipds are mixed/shaken with water (sheet)
alternatively, two-layered structures may form in sheets, these are called phospholipd bilayers which is the basic structure if the cell membrane
what happens the phospholpid bilayer forms compartments
the bilayer forming the cell surface membrane establishing the boundary of each cell
what do internally, membrane-bound compartments provide
internally, membrane bound compartments formed from phospholipd bilayers provide the basic structures of organelles, allowing for specialisation of processes within the cell
why is the lysosome a membrane bound organelle
contains hydrolytic enzymes that need to be compartmentalised to prevent breakdown of most cellular components
are proteins in the phospholipd bilayer
yes
what types of proteins are in phospholipd bilayer
-intrinsic (integral)
-extrinsic (peripheral)
how are intrinsic proteins embedded in the membrane
arrangment determined by hydrophilic and hydrophobic regions
where are extrinsic proteins found
on the inner or outer surface of the membrane
why is the fluid mosaic model described as fluid
-phosophlipds and proteins can move around via diffusion
-the phospholipods mainly move sideways within their own layers
-the may different types of proteins interspersed throughout the bilayer move about within it (although some may be in a fixed position)
why is the fluid mosaic model described as mosaic
the scattered pattern produced by the proteins within the phospholipid bilayer look like a mosaic when viewed above
