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Every living thing is surrounded by a
membrane. This is called the plasma
membrane or the cell surface membrane.
· Membranes are also found inside some cells.
· Some organelles have two membranes
surrounding them, this makes them an
envelope.…read more

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Functions of membranes!
· Membranes are partially permeable and so
control what passes through them.
· Membranes produce different compartments
inside cells
· Membranes are important in cell signalling
· Membranes can allow electrical signals to pass
along them
· Membranes provide attachment sites for
enzymes and other molecules in metabolism…read more

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Structure of cell membranes
· All cell membranes have a similar structure.
· They are all between 7nm and 10nm thick.
· They are formed from a double layer of
molecules called phospholipids, in which there
are many different proteins situated.…read more

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Phospholipid bilayer
· Phospholipids' heads have a tiny charge and
this attracts them to water molecules.
· Their tails don't have a charge and so they are
repelled from water molecules. Hydrophobic
· The phospholipids arrange themselves in a
double layer with the tails facing inwards and
the head outwards. This is because of the
water content in the cell.…read more

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Other components of a cell membrane
· The structure of the plasma cell membrane is
called the fluid mosaic model.
· Membranes also contain cholesterol ­ helps
to maintain the fluidity of the membrane.
Stops is becoming too stiff when cold and
then too fluid when hot.
· There are proteins with sugar molecules
attached called glycolipids and glycoproteins.
The functions of these are on the next slide.…read more

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