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Summary AQA ALEVEL BIOLOGY NOTES ON DIFFUSION AS LEVEL

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ALEVEL NOTES ON THE CELL TRANSPORT TOPIC- DIFFUSION ADJUSTED TO THE AQA SPECIFICATION AND MADE FROM MARKSCHEMES

Institution
AQA

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Diffusion =
Diffusion the of from highly
is net movement molecules ions region where
they are more
-


or a


concentrated to one where their concentration is lower until distributed
evenly .




I T
A BB00
-




Diffusion
' I. Simple ( lipid diffusion )
000
'


I /
"" ← to x




|
I L

Simple diffusion when diffuse cell
f- is
particles across
.

- -
- - - - . .
can

>
I membranes without the help of transport proteins .




4) ,
Fick 's law Rate of diffusion =
Cone .
diff X Surface area

diffusion distance
Dynamic Equilibrium


dynamic
'
.


in
' high concentration equilibrium
gradient faster
' - -
- - - - - - -
n
,
'
.
I
\




Inside outside Inside outside



low concentration dynamic
equilibrium
-

gradient - - - - - .
- - -
-
n
,
-
-
-




slower
>




Inside outside Inside outside




§
'


2 Facilitated Diffusion
.




I
, T



Facilitated diffusion is diffusion proteins and channels
using protein


carrier .





The
transport tend to be specific for molecule
proteins one
,
so substances can
only cross a


membrane that contains an
appropriate protein .




This diffusion inbuilt kinetic of
is the the
diffusing molecules




passive process only
a it relies on
energy
-

.




There is no external input of ATP from respiration .




end
channel hydrophilic
t.IM?isnsdeinngse.smi%ae
proteins




channels
-


They form

and
water


allow
-
filled

specific
hydrophilic
water-soluble ions
If \ If If
[ \ If If \ \ If If \ If If
through
/
to
pass
/
.




The bind with the protein it
ions
causing
-




NOI channel
to conformational hydrophobic -



gated Gated channel

carry change .



end



[ BI9
Carrier proteins

4"


{ /
When such specific
-



a molecule as glucose
to the protein
Conformational
is present ,
it binds

that
with

the
protein .



If If If If If If If If If \ \ If \ If
change occurs
-




released
1
molecule is inside of the membrane

.




kinetic of
Only molecules drive
changed site
-




the
energy process .




binding

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