ocr as biology unit 1

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Uni
t
O ne:
Cel
ls,
Exchange
and
Tr
ansport [BIOLOGY REVISION NOTES]
CELL STRUCTURE
CELL THEORY:
Str
uctur
a l
and
funct
ional
uni
t
of
all
l
i
ving
thi
ngs
New
cell
s ar
ise
fr
om alr
eady exi
sti
ng cel
ls
Cell
sc
o nt
a i
ni
nfor
ma t
iont
hat
inst
ruct
sg
r owth.
Thi
si
nf
ormat
ionc
anb
ep
assedo
nt
o
new cel
ls.
MICROSCOPES:
Ther
e ar
e t
w o
ma i
n t
ypes of
micr
oscopes:
Light and
Electron
El
ectr
on Mi
crographs shown i
n col
our
LI
G HT ELECTRON
Uses
beam of
li
ght Transmission Electron Scanning Electron
Magni
fi
cati
on =
x1500 Microscope (TEM) Microscope (SEM)
Resol
uti
on
=
200 nm
Wide range of
specimens can be used
Samples are fairly
quick + easy to prepare
Cheaper and safer
Limited resolution
Limited magnification
Uses electromagnets t o focus Scan beam of el
ect
rons
beam of electrons acr
oss speci
me n
Denser p a r
ts o f s p eci
me n B eam bounces off
absorb more electrons creat
ing surface of
speci
me n
contrast Produces
3D image
Can o n l
y b e u s ed o n thin Magnif
icat
ion
=
x100,
000
specime ns Resolut
ion = 5 n m
Produc es 2D ima ge (
lower)
Ma gnif
icati
o n
= x500,000
Reso l
ution = 0.2 nm
Ad vant
a ge s Disadvan t
a ges
Can produce coloured Mu st beu
s e di
nav
a cuum (
no
images ai
r)e
l e ctr
o ns a r
e absorbed by
Better resolution molecu l
e s
in
a i
r
Better magnification Expe nsive
Trai
n i
n g i
s r
e quir
e d
Na t
ura l
col
o urs
c an'
t be
seen
Da nge r
o us kil
ls
livi
ng cel
ls
1
|
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Uni
t
O ne:
Cel
ls,
Exchange
and
Tr
ansport [BIOLOGY REVISION NOTES]
STAINING:
U sed t
o
have bett
er
visual
isat
ion
of
cell
s under
a micr
oscope
U sed because some
cell
components
are t
ransparent
A CE TIC OR CEIN
stai
ns DN A
dark r
ed
G EN ET I
AN
V I
O LET
stai
ns bacter
ial
cel
l
w al
ls
I O DINE st
ains
starch
granules
ME T HY LEN E
B LUE/EO SI…read more

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Uni
t
O ne:
Cel
ls,
Exchange
and
Tr
ansport [BIOLOGY REVISION NOTES]
Prot
ect
s agai
nst
mechani
cal
damage
Cel
l Sur
face Made o f
li
pids and Contr
o l
s move ment of
Memb r
ane pr
otei
ns subst
ances i
n and
ou t
of
cel
ls
Has r ecept
or mo l
ecules that
al
lowsi
ttor
espondt
oc
hemicals
(
hormo nes)
separat
e c ell
c on t
ents from
out
side
the
cell
separat…read more

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Uni
t
O ne:
Cel
ls,
Exchange
and
Tr
ansport [BIOLOGY REVISION NOTES]
Synthesi
s,
st
oresa
ndt
ranspor
ts
car
bohydrat
es
Stack of membr
ane Receives and mo di
fi
esp
r ot
eins
bound
sacs f
rom ER
Packages mo dif
ied prot
ein i
nto
vesi
cl
es t
o be t
ransport
ed
Gol
gi
Appar
atus Makes l
ysosome s
Produces
secret
ory enzymes
Vesi
cl
e Sma l
l
f l
uid sac in T ranspor
ts
subst…read more

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Uni
t
O ne:
Cel
ls,
Exchange
and
Tr
ansport [BIOLOGY REVISION NOTES]
Have2mi
c r
otubul
esi
n Used li
ke out
board mo t
ors to
cent
re pr
opelc
e l
l
s forwar
d (
e.g.…read more

Page 6

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Uni
t
O ne:
Cel
ls,
Exchange
and
Tr
ansport [BIOLOGY REVISION NOTES]
1) Mi crotub ul
es a n d mi c r
o f
i
lame nts support t he
o rganell
e s keepi
n g
th em in position
2) H elp
strengthen t
he cel
l
a nd maintain its shape
3)R espo ns i
b l
ef
o r
the transport of materials wi
th i
nt h e
c el
l
4)H elpt
hec e l
l
to…read more

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Uni
t
O ne:
Cel
ls,
Exchange
and
Tr
ansport [BIOLOGY REVISION NOTES]
To
fr
agil
e and
simple
to
carr
y out
al
l
funct
ions
Many ot
her
comp onent
s ar
e needed t
o enabl
e f
unct
ions
of
membr
ane
STRUCTURE:
Memb ran e
co nsi
st
of
arranged
phospholi
p i
ds
Head is
hydrophilic
attr
acts
water
Tai
l
is hydrophobic
repel
s water
Molecu l
es arrange themse l
vesi
nt
oa bilayer t
he heads…read more

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Uni
t
O ne:
Cel
ls,
Exchange
and
Tr
ansport [BIOLOGY REVISION NOTES]
Carrier:
Actively transport s ubstances
across
membrane
(r
equi
res
ATP
)
A cta
s receptor sites formo
l ecul
es t
o bind t
o pr
otei
n,s
o cel
l
resp onse
can be
c arried
out
Funct
ion
as enzymes
Provi
de
str
uctur
al suppor
t
Cholesterol Provi
des st
abil
i
ty
(eukaryot
ic
cel
ls)
Reduces l
ater
al
mo veme nt
of
phosphol
ipi
ds…read more

Page 9

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Uni
t
O ne:
Cel
ls,
Exchange
and
Tr
ansport [BIOLOGY REVISION NOTES]
1)B acter
ia
kn own
as "Clostridium Buctucinium"
2) Releases protein
that
binds r ecept
ors
on mu scl
e cel
ls
3)R esult
=
p ar
a l
ysis
IMPERMEABILITY OF CELL MEMBRANES:
C e l
l
su rface me mb rane
is
impermeab le
to mo st mo lecule s
T he y'
re not soluble and
ther
e f
ore
ca n not pass
thro ugh p ho spho…read more

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Uni
t
O ne:
Cel
ls,
Exchange
and
Tr
ansport [BIOLOGY REVISION NOTES]
A gai
nst
concentr
a t
ion
gradient
R equi
res
A TP t
o ma ke
process "
acti
ve"
Invol
ves car
ri
er pr
o t
eins
P r
otei
ns act
as
"pump s" which
are complementar
y
Mo l
eculea
ttachest
oc
a rr
ierp
rotei
na
n dp
rotei
nc
hangess
hape,t
henmo
ves
mo l
ecul
e
across
me mb rane
releasi
ng i
t…read more

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