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2.5 Biological Membranes: Revision Summary Sheets for A-Level Biology (OCR A Module 2)

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Comprehensive handwritten summary notes covering Module 2: Foundations in Biology for OCR A A-Level Biology. These notes were created and used for revision in the 2024 exam series, in which I achieved a high A grade, close to an A*. The notes are designed to provide a clear and concise overview of the entire module, including: * Cell structure and ultrastructure * Biological molecules * Nucleotides and nucleic acids * Enzymes * Cell division, cell diversity, and cellular organisation Features: * Easy-to-follow handwritten format * Exam-focused content based on the OCR A specification * Concise explanations suitable for revision and recap * Useful for both first learning and final exam preparation These notes are intended to help students quickly review the most important concepts from Module 2 and build a strong foundation for success in OCR A A-Level Biology. Disclaimer: These notes are my personal revision materials and are not endorsed by OCR. They should be used alongside the official specification, textbooks, and other revision resources.

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Biological Membranes
5




molecule .
glycocalyx ,
(carbony date 2 .




Fluid Mosaic Model :
Chydrophobic
2
Active Processes Substance Direction Passive ? other info


o ⑳ i
ogiyprotein need
-




colipid
Goy ATP
:

Diffusion molecule > low n19
high
-




no
·
-
>
attached lipid.
- peripheral protein . Facilitated molecule ATP
high low no
through carrie
· -
L




bilayer
g
9909

antigens


E
↳ enzymes site diffusion proteins.
phospholipid ↳ receptor
down 4 ATP
water molecules no
partially permeable
·
Osmosis a


& $62 nyarophobic
fatty acid tail low
gradient
ATP
membrane
active molecule -
high . protein carriers.
W




s protein &
a
channel carrier
Clons) transport
hydrophilic phosphate
-




protein
↓ mechanical head .
molecules facilitated diffusion : FACTORS AFFECTING
Stability ,
regulates
fuidity across a
partially permeable
NO ATP required DIFFUSION :

in
-
neurones :
membrane via protein channels -




only ninetic
energy * the diffusion
bigger the
:
-




Myclin Sheath flattened cells wrapped around several times . or carriers distance the slower the

special that enable to be
protein receptors antigens rate.
-




recognised.
be
may
or
may not
Diffusion molecules more *
larger SA
,
more diffusion
down a water potential across a membrane from high to low * temprature increases

gradient concentration diffusion


saresante
water molecules the
*
Steeper the
gradient
the faster the rate



across
⑮ mosis
the concentration
* smaller molecules diffuse
a solution
against more
rapidly
partially permeable -
4 0
dilute concentrated gradient
membrane = : isotonic
hypotonic hypertonic
↳ ↳



across a cell bulk transport :



requires
ATP
Active
Transport membrane used to transport
Hypotonic Hypertonic Molecules too
large to

the
pass through

Animal" -
carrier
the
proteins

energy
conformation I
from
:




snape .
ATP helps
ENDOCTTOSIS
-
:
plasma
=>
requires
membrane .
ATP .




cytolysed crenated ERMEABILITY :
now particles are
D ExOCTTOSIS :


* temprature cell .
:
brought into a now
large



plant
=> drops solid molecules are
phagocytosis
: =



saturated become compressed . liquid
fatty acids exported.
·



pinocytosis
=




ounsaturated
fatty acids become with the



-
fuses
-




O
compressed ↓the winus in their tail plasma membrane
the advacent phospholipid away




i
pushes . rescile
* Proteins a temprature :
>
maintains
fluidity .
-




·
can unfold
·
cholesterol buffers temprature
↳ wean It bonds ionic bonds . reduction .
fuidity

prevents a in
·
can denature .

prevents the phospholipids from
threads
cytoskeleton are
packing too
closely together .
·




proteins . => increases :

·
phospholipids acquire more linetic
energy a moves
randomly
.

↳ increases
fluidity 2 permeability
.
·
cholesterol molecules buffers .

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Number of pages
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Written in
2023/2024
Type
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