topic 2 : cell membrane
Plasma membrane :
Only allows specific substances through
i
Passes messages from external environment to cell 's interior
•
.
Functions :
between internal and external environments of cells
Boundary
•
.
↳ continuous double layer of phospholipid molecules makes
boundary
'
communicates with other cells
\
'
Regulars exchange substances in and out of the cell .
.
biomolecular _
•
chemical reactions occur on it
.
ftp.ct .
'
Receptor site for recognising stimuli
•
this space
Not only semi permeable but differentially used for
-
,
permeable : communication
Only allows certain molecules through
'
cell maintains its internal order irrespective of changes in the environment
•
.
↳
eg substances may need to be imported / exported from the cell depending on its
:
metabolic activity
This allows the cell to exercise control over the quantum timing and rat of movement
•
,
of these molecules .
Plasma membrane is :
differentially permeable all work
'
↳ allows the
rapid entry of some molecules and the gradual or slow entry together
other molecules .
at the
2
semi permeable ( selective ) same time
-
impermeable
3
EfETfAEtEEOdE
E-
,The fluid -
mosaic model .
Channel glycolipid glycoprotein
phospholipid protein " "" """ ^
Y.LY?oa.gm*agg*.omymGL@ Y%18.a.am#aae*PEmIad integral protein
••oÉo•TMMµqgq•••••o
0m£
:•↑MMaIBa1[ a
qooalphospnakheadi.io?!j.Km E-4aa. f i ? . : .o. a oaE. : . !
• •••••••• •
" t !•!•"t t / 44 1144948444 tatyacidtails
ÑMCaaooooa\e
.
.
' ' cholesterol
integral proteins
peripheral aquaporin
protein
the plasma membrane is . . .
.
Phospholipid bilayer :
differentially permeable
'
↑f
↳ allows the
rapid entry of a " work polar hydrophilic head
some molecules and the
gradual orslowentryot
together
at the
saturated faltyacidtail
unsaturated faltyacidtail /
" " ""b "
,apya,a
other molecules .
sometime
permeable / selective ) stops entry of polar / Charged molecules
2
semi
'
-
.
impermeable Allows entry of non polar molecules
' •
-
_
leg steroids / to pass through
:
[ no , ,µµ , •
mamngammmangg.name ,
At high temperatures tails increases fluidity
Formsmicellesinwatrfor④
☒
-
§
,
it increases intermolecular
-
kinkisformedduetothe
and decreases fluidity unsaturated fatty acids and prevents
•
Atlowtmperatures ,
⑥ 10h11 polar dose packing and forms weak Van
vice versa and prevents derwaa / interactions (cell membrane
freezing .
has the same consistency otoliveoil ) .
Transmembrane proteins ( integral / intrinsic) Glycolipids
: :
Aquaporins
'
Added carbohydrate chaintolipid
↳ in bacteria animal and plant cells
,
'
cell to cell attachment
transport of water by electrostatic forces cell to cell recognition / eg blood group )
↳ -
:
.
↳ impermeable to charged ions Glycoproteins :
Channel /tordittosion) Added carbohydrate chain to protein
'
.
↳ transports ions self-recognition leg :MHC proteins
'
open on both sides recognised by immune system )
↳ .
↳ inside of protein is oppositely charged to
the ions that pass
through it .
carrier / fora.HU/0nandactivetransport) Peripheral (extrinsic) proteins :
↳
transports molecules ( lewcanpassatthesame Enzymes
'
time) .
↳ chemical reactions occur
↳
gate open orclosedataltematends ↳ in mitochondria and chloroplasts .
Receptors
↳ binds to hormones and neurotransmitters
, the lipid part of the membrane
The membrane has non polar portions containing lipids and a proof is that organic solvents
•
-
( except alcohol and ether) penetrate membranes more readily than water
•
Polar groups molecules possess
or an uneven distribution of charge and are hydrophilic
( have an affinity for water ) .
Non polar groups or molecules are hydrophobic ( do not mix with water )
- -
.
Phospholipids are amphi thetic ( molecule which has hydrophilic and hydrophobic
-
parts ) They are the most common lipids
.
.
↳ are
spread over the surface of water
↳ arrange themselves into a single layer
↳ the non -
polar hydrophobic tails project out of the water
↳ the polar hydrophilic heads lie in
It present in large enough amounts particles called micelles are formed
phospholipids are
•
.
and the hydrophobic tails project inwards away from the water forming a bilayer
, , .
↳ the basic structure
of a cell membrane
Detergents that are amphi the tic and also form micelle penetrate the bilayer and dissolve the
•
,
phospholipids .
↳ can move in three ways :
lateral diffusion (sideways )
'
2
rotation
3
flip flop (shifting place) .
↳
arrangement
stay intact when the cells move
the cell will
•
hydrophobic tails stop the passage of water soluble substances making the cell
'
,
membrane selectively permeable .
-
The cell membrane is badly damaged with polar solvent .
↳ acetone ethanol and other solvents denature
, proteins by disturbing hydrogen bonds
and hydrophilic Van der Waal interactions ?
↳ holes form in the cell membrane
Plasma membrane :
Only allows specific substances through
i
Passes messages from external environment to cell 's interior
•
.
Functions :
between internal and external environments of cells
Boundary
•
.
↳ continuous double layer of phospholipid molecules makes
boundary
'
communicates with other cells
\
'
Regulars exchange substances in and out of the cell .
.
biomolecular _
•
chemical reactions occur on it
.
ftp.ct .
'
Receptor site for recognising stimuli
•
this space
Not only semi permeable but differentially used for
-
,
permeable : communication
Only allows certain molecules through
'
cell maintains its internal order irrespective of changes in the environment
•
.
↳
eg substances may need to be imported / exported from the cell depending on its
:
metabolic activity
This allows the cell to exercise control over the quantum timing and rat of movement
•
,
of these molecules .
Plasma membrane is :
differentially permeable all work
'
↳ allows the
rapid entry of some molecules and the gradual or slow entry together
other molecules .
at the
2
semi permeable ( selective ) same time
-
impermeable
3
EfETfAEtEEOdE
E-
,The fluid -
mosaic model .
Channel glycolipid glycoprotein
phospholipid protein " "" """ ^
Y.LY?oa.gm*agg*.omymGL@ Y%18.a.am#aae*PEmIad integral protein
••oÉo•TMMµqgq•••••o
0m£
:•↑MMaIBa1[ a
qooalphospnakheadi.io?!j.Km E-4aa. f i ? . : .o. a oaE. : . !
• •••••••• •
" t !•!•"t t / 44 1144948444 tatyacidtails
ÑMCaaooooa\e
.
.
' ' cholesterol
integral proteins
peripheral aquaporin
protein
the plasma membrane is . . .
.
Phospholipid bilayer :
differentially permeable
'
↑f
↳ allows the
rapid entry of a " work polar hydrophilic head
some molecules and the
gradual orslowentryot
together
at the
saturated faltyacidtail
unsaturated faltyacidtail /
" " ""b "
,apya,a
other molecules .
sometime
permeable / selective ) stops entry of polar / Charged molecules
2
semi
'
-
.
impermeable Allows entry of non polar molecules
' •
-
_
leg steroids / to pass through
:
[ no , ,µµ , •
mamngammmangg.name ,
At high temperatures tails increases fluidity
Formsmicellesinwatrfor④
☒
-
§
,
it increases intermolecular
-
kinkisformedduetothe
and decreases fluidity unsaturated fatty acids and prevents
•
Atlowtmperatures ,
⑥ 10h11 polar dose packing and forms weak Van
vice versa and prevents derwaa / interactions (cell membrane
freezing .
has the same consistency otoliveoil ) .
Transmembrane proteins ( integral / intrinsic) Glycolipids
: :
Aquaporins
'
Added carbohydrate chaintolipid
↳ in bacteria animal and plant cells
,
'
cell to cell attachment
transport of water by electrostatic forces cell to cell recognition / eg blood group )
↳ -
:
.
↳ impermeable to charged ions Glycoproteins :
Channel /tordittosion) Added carbohydrate chain to protein
'
.
↳ transports ions self-recognition leg :MHC proteins
'
open on both sides recognised by immune system )
↳ .
↳ inside of protein is oppositely charged to
the ions that pass
through it .
carrier / fora.HU/0nandactivetransport) Peripheral (extrinsic) proteins :
↳
transports molecules ( lewcanpassatthesame Enzymes
'
time) .
↳ chemical reactions occur
↳
gate open orclosedataltematends ↳ in mitochondria and chloroplasts .
Receptors
↳ binds to hormones and neurotransmitters
, the lipid part of the membrane
The membrane has non polar portions containing lipids and a proof is that organic solvents
•
-
( except alcohol and ether) penetrate membranes more readily than water
•
Polar groups molecules possess
or an uneven distribution of charge and are hydrophilic
( have an affinity for water ) .
Non polar groups or molecules are hydrophobic ( do not mix with water )
- -
.
Phospholipids are amphi thetic ( molecule which has hydrophilic and hydrophobic
-
parts ) They are the most common lipids
.
.
↳ are
spread over the surface of water
↳ arrange themselves into a single layer
↳ the non -
polar hydrophobic tails project out of the water
↳ the polar hydrophilic heads lie in
It present in large enough amounts particles called micelles are formed
phospholipids are
•
.
and the hydrophobic tails project inwards away from the water forming a bilayer
, , .
↳ the basic structure
of a cell membrane
Detergents that are amphi the tic and also form micelle penetrate the bilayer and dissolve the
•
,
phospholipids .
↳ can move in three ways :
lateral diffusion (sideways )
'
2
rotation
3
flip flop (shifting place) .
↳
arrangement
stay intact when the cells move
the cell will
•
hydrophobic tails stop the passage of water soluble substances making the cell
'
,
membrane selectively permeable .
-
The cell membrane is badly damaged with polar solvent .
↳ acetone ethanol and other solvents denature
, proteins by disturbing hydrogen bonds
and hydrophilic Van der Waal interactions ?
↳ holes form in the cell membrane
