Summary Topic 2 Cell Transport

Cell Transport
Membrane 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
-