AQA Biology Unit 2 Revision

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Cel
ls
All
an i
ma l
s
and plan t
s are ma de up of
cell
s.
They al
l
co ntai
n :
nucleus,
cytopl
asm,
cell
me mb r
an e,
mit
o c h ondri
a and ri
b oso me s.
Yo u
h ave
to
b e
able
to
d r
aw
an d
label
an animal
ce l
l
or
a plant
cell
.
A
plant
cell
has a
c oup l
e mo r
e
fe at
u res:
cel
l wa l
l
, per
ma nent
vacuo l
e
a nd chl
oroplast
s. They al
l
have functi
ons and
t
he se
a re di
splayed i
n the t
a bl
e b el
ow .
Name Description
Nucleus Thi
s conta i
ns
the cel
l'
s geneti
c materi
als
(D NA) and cont
rols
t
he cell
's acti
vit
ies.
Cytoplasm Thi
s i
s
w he r
e
mo st
of
the chemical
processe s
take pl
ace,
it
i
s
t
he base
o f
the cel
l
and
control
led
b y
enzyme s.
Cell membrane Thi
s controls t
he
mo veme nt
of
sub st
ances
in
an d
o ut
of
the
cel
l.
Mitochondria Thi
s i
s
w he r
e
mo st
energy i
s r
e l
eased
by respi
rati
on.
Ribosomes Thi
s i
s
w he r
e
protei
n synthesi
s occurs wh ere
protei
n i
s
made .
Permanent vacuole Thi
s i
s
fi
ll
e d wit
h cel
l
sa p
(ma de of
mo st
ly
w at
e r
and
di
ssolved
su gars)
to
ma ke t
he
cell
t
urgid.
Cell wall Thi
s i
s
ma de of
cell
ulose
(ri
gid
layer)
and thi
s supports
and
st
rengthe ns t
h e
cell
Chloroplasts Thi
s conta i
ns
chlorophyl
l
an d
ab sor
bs sunli
gh t
f
or
phot
o synthes i
s.
The se are
u sed f
or regu l
ar cel
ls
but
cell
s t
hat
requi
re a certain
functi
on are
spe ci
ali
sed.
Spe cia l
ised cel
ls:
Name Function
Sperm cell Thi
s has a
tail
which
h el
ps i
t
sw i
m.
Function: to fertilise the egg The `
he ad'
co ntai
ns t
he
nucleus which
ha s
23
chromo some s.
I
t
also has
en zyme s
w hi
ch help
digest
the egg cel
ls
memb ran e.
Egg cell The egg ce l
l
is
surrounded in
nutri
ents
w hich
w i
ll
help
deve l
op
t
he emb ryo .
I
t
also has
a nucleus which
co nt
ains
2 3
chromo some s.
Red blood cell I
t
has no
n ucleus so
there
is
mo re space
for haemo gl
o bi
n.
Function: to drop off oxygen There i
s a con cave
sha pe
a nd
thi
s all
ow s
mo re oxygen t
o be
absorbed
mo r
e eff
ici
entl
y.
Nerve cell I
t
contains
ma ny of
the necessi
ti
e s
of
an
anima l
cell
:
nucleus,
cyt
oplasm an d
cell
me mbrane .
The nerve
ce l
l
also
has an axon (
b ody)
. Recep t
ors which
are
used
to pick up me ssages.
I
nsulati
on (
co at
ing)
to st
op the
me ssage getti
ng l
os t
.
Cilia I
t
has mic roscopic
h ai
rs
w hi
ch w af
t
back and
fort
h any di
rt
Function: to line the airways et
c.
ba ck to
the nose and mo ut
h. I
t
also
p r
od uces mucu s
to
t
rap anything to
stop i
t
gett
ing i
nto t
he l
un gs.
Muscle cell The st
ruc t
u r
e
is
to
a l
l
o w t
he mu scl
e t
o
mo ve.
T her
e
are al
so
l
ots
of mitoch ondri
a f
or r
eleasing
e ner
g y
fr
o m respi
rati
on.
Root hair cell Thi
s i
s
on ly
in
p l
ants.
They are no
chloropl
a st
s l
ike nor
ma l
Function: to absorb water pl
ant
c el
ls be cause
it
i
s unde r
ground.
So
they are
no t
needed
because p hotosynthesi
s doesn't
occur
u nderground (
n o
sunl
ight
a vail
a bl
e)
a nd
they need mo r
e space to
ab sor
b
w at
er.
There i
s also a l
arger
surface
a r
ea wh i
ch i
s so more water
is
col
lect
e d.
White blood cell Thi
s has a
diff
erent
n ucl
eus fr
om r
egu l
ar
a ni
ma l
cell
s and t
his
i
s becaus e i
t needs t
o noti
ce di
ff
e r
ent f
oreign
b odi
e s.
Al
so the cell
me mb r
a ne
cha nges shape and engulf
s bacter
ia
and
viruse s.

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Page 2

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Guard cell Thi
s i
s where
the
oxygen goes
out
and t
he carbon
dioxi
de
goes
in.
They
are on
the
bott
om of
the
leaf
as
it
i
s sensi
ti
ve
to
sunl
ight
and
if
i
t
is
under
the
leaf
t
here
is
less
exposed.…read more

Page 3

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Enzymes
E n zyme s a r
e bi
o logi
cal
catalyst
s,
thi
s me ans
that
they speed up a r
eacti
o n
w i
thout
cha ngi
ng. They
a r
e
ma de of
struct
ur es
o f
pr
oteins.
A c ti
ve si
te is
w h er
e the
mo l
e cul
es get
digest
e d.…read more

Page 4

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Byproducts are cleared away
Di
gest
ion
Wh en
food i
s bei
ng chew ed,
t
h e
food
g et
s br
o ken
d own sl
ow l
y and sal
iva
softens
the good and
a n
enzyme
i
s r
eleased cal
led
amy l
a se,
t
his
is
a carbohydrat
e .
The f
oo d
goes dow n
through t
he oesoph agus
and thi
s
squeezes t
he f
o od
dow n.…read more

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Page 6

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Page 7

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Page 8

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Fact
ors
li
mit
i
n g
phot
osynt
hesi
s…read more

Page 9

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Nutrients needed for healthy growth:
Mineral What does it do? What happens if it becomes
deficient?
Nitrogen Makes
amino aci
ds f
or gr
ow t
h Poo r
g r
ow t
h .
and
repai
r.
Potassium So
enzyme s
can work Yellow
leav es
and dead
spots.
ef
fi
ci
entl
y.
Phosphorus Requi
red
for
respi
rat
ion
a nd Y ellow
leav es
w i
th
purpl
e s
p ot
s
phot
osynt
hesis.…read more

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Except
f
or
ident
ical
t
w i
ns,
each
person'
s DNA
is
unique.
Thi
s i
s why peopl
e can
be i
denti
fi
ed usi
ng
D NA
f
i
n ger
pri
nti
ng.
D NA can
be cut
up
and separ
ated,
for
ming a
sort
of
'
b ar
code'
t
hat
is
dif
fer
ent
fr
om one
per
son t
o t
he next
.…read more

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