As level Biology
AQA
, plasma membrane is a partially permeable barrier. Controls which substances enter + leave
·
the cell.
·
Membranes around organelles divide cell into diff compartments :
ex .
lysosome , vacuole , endoplasmic reticrium
.
·
substances can more across membranes by diffusion ,
osmosis or active transport.
·
organisms like mitochondria + chloroplasts have a double membrane
function
·
membranes control movement of substances across them
· Control passage of substances int out of cells +
organelles .
separate
·
content of cells from their environment
separate diff areas with cells
·
·
separate diff areas within diff organelles
·
provide a surface for attachment of enzymes + receptors
.
The diff component of cell membranes have diff roles
Lipids
phospholipid bilayerIs thin polar membrane made of phospholipid · Forms a
molecules good
·
a two layers of
barrier between interior exterior of cell because water + other polar charged substances which cannot
easily cross the hydrophobic fatty acids talls in centre of membrane
phospholipid bilayer
two hydrophobic fatty acid talls
hydrophilic heads
polar
·
phospholipids are described as amphipathic which means they consist of a hydrophobic+ hydrophilic
head .
·
hydrophobic tails turn towards each other so that they face away from the water . Polar heads
turn to face the water to form a bllayer.
·
phospholipid bilayer is flvid as molecules are constantly moving around in relation to each other
.
Cholestero
·
lipid with my drophobic + phillic end. Regulates the firidity of the membrane. Positioned between
phospholipids preventing them grouping too closely +
crystalising + so maintaining fluidity at low temp
· at high temp they restrain movement.
,
AQA
, plasma membrane is a partially permeable barrier. Controls which substances enter + leave
·
the cell.
·
Membranes around organelles divide cell into diff compartments :
ex .
lysosome , vacuole , endoplasmic reticrium
.
·
substances can more across membranes by diffusion ,
osmosis or active transport.
·
organisms like mitochondria + chloroplasts have a double membrane
function
·
membranes control movement of substances across them
· Control passage of substances int out of cells +
organelles .
separate
·
content of cells from their environment
separate diff areas with cells
·
·
separate diff areas within diff organelles
·
provide a surface for attachment of enzymes + receptors
.
The diff component of cell membranes have diff roles
Lipids
phospholipid bilayerIs thin polar membrane made of phospholipid · Forms a
molecules good
·
a two layers of
barrier between interior exterior of cell because water + other polar charged substances which cannot
easily cross the hydrophobic fatty acids talls in centre of membrane
phospholipid bilayer
two hydrophobic fatty acid talls
hydrophilic heads
polar
·
phospholipids are described as amphipathic which means they consist of a hydrophobic+ hydrophilic
head .
·
hydrophobic tails turn towards each other so that they face away from the water . Polar heads
turn to face the water to form a bllayer.
·
phospholipid bilayer is flvid as molecules are constantly moving around in relation to each other
.
Cholestero
·
lipid with my drophobic + phillic end. Regulates the firidity of the membrane. Positioned between
phospholipids preventing them grouping too closely +
crystalising + so maintaining fluidity at low temp
· at high temp they restrain movement.
,
