Summary
Summary Topic 2 Cell Transport
Edexcel Biology Topic 2 Cell Transport, Diffusion, Osmosis, Active Transport, Exocytosis and Endocytosis
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Cell TransportMembrane To
freely without assistance Can't be to
·
move across membrane molecules
Permeability large
S.I units ·
Small non-polar , lipid soluble hydrophobic molecules can diffuse freely
across the membrane (O2 CO2 hormones (
, ,
Polar molecules bilayer
typically can't cross the phospholipid they repelled
·
as are
by fatty acid hydrophobic centre
.
Some the
small polar molecules diffuse at
·
can across membrane
a slower rate
·
lons can't move across the membrane as
they are repelled
(impermeable)
Large molecules like (glucose) can't
diffuse freely
-
Passive Transport
without
Diffusion -net movement of molecules and ions down a concentration gradient requiring
energy
Passive -
no input of metabolic energy (ATP)
-
is
Diffusion
O
continues until equilibrium is reached and net movement
Facilitated of
-net movement molecules and ions down a concentration
gradient
diffusion requires channel or a carrier protein across a semi-permeable membrane
Channel Protein
-
protein with a pore in the middle of it
ion
-
specific
Carrier proteins
-
>
passive (downhill) transport glucose (specific
-
binding site
-
protein changes shape
> outwards to
binding site changes - inwards
-
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