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Summary - 2.1.5 Biological Membranes

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Provides an in depth, comprehensive and high-yield summary for A - Level biology, specifically tailored to OCR A specification. These notes compile information from the official textbook, mark schemes, and class lectures into a concise revision resource. Includes: Coverage of all points on the specification for 2.1.5 Biological Membranes Definitions for key terminology required by examiners Clear, labelled diagrams for complex processes

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TYPE 2
Structure and function Facilitated diffusion carrier proteins. Small molecules + some large ones Active transport
·
barriers -
compartmentalisation -

organises internal environmentinto ·

passive diffusion ·specific shape which changes once a molecule ·

requires energy -> ATP
separate sections, partially permeable -

only allows certain things in/out
·
uses intrinsic
proteins as they binds to it 29 11(o) againstthe concentration gradient
·site of chemical reactions- keep things together needed for chemical can't
interactwith the hydrophobic carries molecules from one side the other
to

0

8
-
-


tails
regions
take two
reactions ribosomes RER keptin place for protein synthesis of the bilayer ↳
co-transporters can at a time 2 specific
·
-
on
-
eg.
O -⑧
cell signalling-helps other cells
recognise types of cells they molecules are
large, polar and ·importantfor reabsorption of glucose + amino ↳ one binds with - -8
high ATP

⑥.
- -




are dealing with liposome/micelle-bundles of lipids that lipid insoluble
I


...........
w
~ · CONC. acids in the kidney molecules, one ⑧
A

8


"On
·000
⑧ 00
TYPE
1
...... high
- 8
PHOSPHOLIPIDS when when
you shake waterlipid Il
allows hydrolysis.


conc
.........
form S
.



y
1

-
...
0
channel low
ATP

.
proteins + lipids most
of the cell membrane proteins Of ⑧


moleculespass
-




phosphore)-hydrophilis C
- CONC.
andi t ->




·
through O
-
soluble substances insoluble

8899,90.f
is impenetrable to -
water polart O




88
1
·water-soluble substances and other molecules ↳ 0.8mm in diameter-diffuse through //I I

initi
000000⑧
samal's water-filled Low conformational
taste
satty-hydrophobic BADP
of proteins
......
made
passage ways
....... .....
- -
use



I
pores of
* able change
I

non-polar, to interactwith water due to the polarity protein CONC. occurs ⑧




d
of
Simple diffusion
/

⑧ 8 ⑧
-
molecule carried
can't form bonds with phosphate ↳ ⑧ ⑧
8
-
o
8

to
passive, along concentration gradient (high-low) other side ⑧



FLUID MOSAIC MODEL molecules continue to until
they in ATP Cadenosine tri-phosphate)
88
move are n-




888
=
equilibrium still but stay roughly equal 3 phosphate -> forms
·goo ⑧ -
- move


-- ⑧
-


ADP
oggggo
-O-0
i- bordroken
-ro
-
-



100ggoogooono8888888888888888888888080880
small non-polar molecules - move through the




ro j WW
·Eggs
-

dine
in hydrophobic
00 oooo tails


1
0 8
oestrogen etc.
Lesteronet e
-

O-
person hydrolysis of ATP
11
↳o
pentosephosphate
1
·

-
ar
some exceptions be
must soluble in lipids 2
·




Dine
-

UJ releases energy -




sugar




want
E 4 . ↑


....
phospholipid bilayer phospholipids
-




able to move, rotate ...
-




Biological
- d



....
↓ & -




and swap places
2 extrinsic protein only -
on one side of the bilayer t membranes Bulk transport ACTIVE
MOVEMENT Water
low
interactwith hydrophilic head conC. EXOC YTOSIS ENDOCYTOSIS potential
iii
3 channel protein -

hydrophilic channel, allows molecules released &
..... I large molecule
:..




Ge
down their the rate of diffusion is 4
movement
of polar molecules concentration directly proportional to:
from the cell
~
...
-



approaches membrane osmosis -
movement
of
gradient throughthe (invaginates)
-

all the way membrane SA 0cOnC. fastest large large membranes of 3 ↑ which dips water across
partially
-
=
a
-




4
carrier protein movement that membrane thickness small ... 2
begins to fold in permeable
vesicleusesweree
-
used for active rate membrane membrane from

FACTORS


requires ATP and involves the protein changing shape AFFECTING DIFFUSION around the large high water potential to low
:
cholesterol-provides mechanical
5
stability, found
·

temperature surface area vesicle moves along ↑
i molecule water potential (Y)
betweenhydrophobic tails, watertions can'tpass concentration. thickness of membrane cytoskeleton
E
highest 4 0kPa
easily : large molecule
· =

3 now

6 PRACTICAL it
glycolipids and glycoproteins -
intrinsic protein with large I inside cell - moved to ↳
pure water

tail cut into differentsized cubes molecules in vesicle it's b
carbohydrate - used in cell
signalling e
receptor sites, agar jelly where needed by adding any solute will
hormones, cell markers or
antigens place in a beaker of hydrochloric acid the
cytoskeleton the water potential
I intrinsic proteins embeddedin the membrane + pass measure the time taken for each cube ATPREQUIRED FOR: Phagocytosis movementof ↳ make it more negative
alcohol
- -




between both layers, called transmembrane proteins to colourless cell surface membrane moves solids across membrane ·
I only ever O
go
tails ↑ SAiratio, I rate
Pintocytosis to the
interact with hydrophobic a diffusion inwards around the molecule movement of Osmosis
·




1,09
of -
moves more


↑ ·when the vesicle moves via liquids across membrane negative water potential
effectof ethanol concentration membrane
&////
on the cytoskeleton
Permeability solvents -
000
permeability
temperature
·

some solvents dissolve METHOD: Effects of osmosis on plant and animal cells
↑11/11/1
0
ANIMALS
-




·5 testtubes of differentconcentrations of

Shie
I
temp-lipids closely
low lipids which increases
hypertonic PLANTS
packed, low permeability
2
high temp-protein's
ddddd permeability
membrane is disrupted
as the
place
ethanol- 0%, 2000, 40%, 60%, 80%, 100%
a
piece of beetroot in each test
tube ·
E
·water moves out of

shrivels up-crenated
cell 88
⑧ hypertonic
plasmolysed water moves out of cell

-
-
-
g
-~
S

~
~

leave

19/9/9/9
↳ phospholipids for 15 minutes Isotonic
·




⑳ same
0
denature, permeability some contents shrink from cell wall


·




a colorimeter with filter Isotonic
·



molecules dissolve creating use a
green netmovement
to polar as no

CONCLUSION:
they protein channels
& gaps more permeable Hypotonic netmovement
-
use ·no

e.g. alcohol higher concentration, more light absorbed


&
↳ Kigh hypotonic -can

·


3
lipids have kinetic and ·water into cell bursting
I




more moves wall stops S




higher

concentration
-




detergents more
permeable bursts
onBois bitonpas
·cell stretchest
=
turgideswell into cell
energymeet
·


up, water moves
-





↳ cytolysis -
hills cell

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