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Cell membranes
- The basics
- Membranes control
what passes through
them
- Cell surface membranes
- Control what substance
enter and leave the cell,
they are partially
permeable
- Allow recognition
by other cells
- Allow cell communication
- Control what substance
enter and leave the cell,
they are partially
permeable
- Membranes within cells
- Around
organelles,
divide the cell
into different
compartmens
- Membranes of some
organelles are folded to
increase surface area to
make chemical reactions
more efficiant
- Form vesicles for transport
- Control what passes
through the organelle
and they are partially
permeable
- Around
organelles,
divide the cell
into different
compartmens
- Cell surface membranes
- Fluid mosaic structure
- Phospholipid
bilayer
constantly
moves. It
contains
cholesterol,
protein
molecules
(glycoproteins)
and (glycolipids)
- Around 7nm thick
- Phospholipid
bilayer
constantly
moves. It
contains
cholesterol,
protein
molecules
(glycoproteins)
and (glycolipids)
- Components
- Phospholipids
- Hydrophilic head and a hydrophobic tail
- Hydrophilic head and a hydrophobic tail
- Cholesterol
- Fits between the
phospholipids
molecules and
makes they
membrane more rigid
and less fluid
- Fits between the
phospholipids
molecules and
makes they
membrane more rigid
and less fluid
- Proteins
- Some form channel proteins that
allow small or charged particles
through
- Carrier proteins transport ions across
- Proteins also
act as receptors
in cell signalling
- Some form channel proteins that
allow small or charged particles
through
- Glyco(proteins/lipids)
- Stabilise the membrane by
forming hydrogen bonds with
surrounding water molecules
- Act as
receptors and
antigens
- Stabilise the membrane by
forming hydrogen bonds with
surrounding water molecules
- Phospholipids
- Membranes control
what passes through
them
- Transport across cell membranes
- Diffusion
- Passive, from high to low
concentration
- Passive, from high to low
concentration
- Osmosis
- Diffusion of water from high
to low water potential across
partially permeable membrane
- Diffusion of water from high
to low water potential across
partially permeable membrane
- Facilitated Diffusion
- From high to low
concentration and it
a passive process.
- From high to low
concentration and it
a passive process.
- Active transport
- High to low concentration,
active process. (ATP)
Using carrier proteins to
change the shape
- High to low concentration,
active process. (ATP)
Using carrier proteins to
change the shape
- Endo/exocytosis
- Bulk transport of
materials fusing to the
membrane
- Bulk transport of
materials fusing to the
membrane
- Diffusion
- Cell signalling and temperature
- Cells
communicate
using
messenger
molecules
- One cells releases
MM, it travels to
another cell, it is
detected by the cell
and binds to its
receptor
- One cells releases
MM, it travels to
another cell, it is
detected by the cell
and binds to its
receptor
- The receptor
proteins have a
specific shape,
a cell that
responds to the
MM is called a
target cell
- Drugs binds to
receptors to trigger a
response
- Below 0C: Membrane doesn't
move. Channel and carrier
proteins denature, increasing
permeability. Ice crystals peirce
the membrane
- 0C-45C: Membrane is partially
permeable, as temperature
increases the membrane moves
more - kinetic energy
- 45C+: Bilayer melts and the
membrane is more permeable,
channel and carrier proteins
denature and increases permeability
- 0C-45C: Membrane is partially
permeable, as temperature
increases the membrane moves
more - kinetic energy
- Cells
communicate
using
messenger
molecules
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