Aqa- B1

Biology unit 1 (AQA)

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  • Created on: 01-01-11 15:48
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Defending against infectious disease:
Pat
h ogens
are
microor
ganisms t
hat
cause
disease.
Pathogens
incl
ude bact
eri
a and
vir
uses.
Bact
e r
ia
rel
eases t
oxi
ns and
vir
uses damage
ou r
cel
ls.
Whit
e bl
ood cel
ls
can dest
roy
and i
ngest
pat
hog ens.
They
can
produce
a nt
ibodi
es
that
dest
roy
p at
hogens,
and ant
it
oxins
that
neut
ral
ise
t
oxins
.
I
n a
vacci
nati
o n,
pat
hogens ar
e i
ntroduced
int
o t
he
body i
n a
dead or
i
nacti
ve
for
m. Thi
s st
imulat
es
t
he body
to
produce enough
w hi
te
blood
cell
s t
o pr
o t
ect
i
tsel
f
fr
om the
p at
hogens,
whi
le
not get
ti
ng
t
he di
sease Anti
bodi
es ar
e onl
y ef
fecti
ve
a gai
nst
bacter
ia,
not
vi
ruses.
Some st
rai
ns
of
bacteri
a ar
e
r
esi
stant
t
o
anti
biot
ics
.
Bacteria:
Bact
eri
a ar
e microscopic organisms.
They
come i
n many shapes
and
s
izes,
but
even
the
lar
ges t
are
only
10
micr
ome t
res
long
10 mil
li
onths
of
a
me t
re
.
Bact
eri
a ar
e living cells
and,
in
favour
abl
e condi
ti
ons,
can
mult
ipl
y r
api
d l
y.
Once
insi
de the
bod y,
they
rel
ease poi
sons
or
toxi
ns
that
make
us f
eel
il
l
.
Di
seases
cau se d
b y
ba ct
eri
a i
nclude
:
f
ood poi
soning
chol
era
t
yphoid
whooping
cough
gonor
rhoea a
sexual
ly
tr
ansmi
tt
ed
disease
Viruses:
Vi
ruses
a r
e
mu ch sma l
ler
th an
bacteri
a.
They consist
of
a
fragment of
genet
ic
ma teri
a l
i
nsi
d e a
p rot
ecti
ve prot
ein
coa t
.
V i
ruses
can onl
y
r
eproduce inside host cells,
and t
hey dama ge t
he cel
l
w hen
they
d o
thi
s.
A
vir
us can
get i
nside
a cell
and,
once t
here,
take
o ver
and
ma ke hundreds
of
t
housan ds of
copies of
itsel
f.
Eventual
ly
the
virus
copies
fi
ll
t
he whole
host
cel
l
an d
b urst
i
t
op en. The vi
ruses
are
then passed out
i
n the
bl
oodstr
ea m. Diseases cau sed by
vir
uses i
nclude:
i
nfl
uenza
fl
u
mump s
, measl
es
and
rubel
la
chi
cken
pox
AI
D S
White blood cells:

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The
body can
protect
i
tsel
f
against
pathogens i
n many di
ff
e r
ent
w ays.
The f
ir
st
defenc e
is
passive
immunity. Thi
s ai
ms
to st
op pathogens f
rom ent
e r
ing
the body.…read more

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Ant
ibodi
es
neu t
ral
ise
pat
hogens
in
a number
of
ways
:
t
hey
bind
to
pathogens
and damage or
dest
roy
them
t
hey
coat
pathogens,
cl
umping
them t
ogether
so
that
they
are
easil
y i
ngest
ed
by phagocyt
es
t
hey
bind
to
the
pathogens
and r
elease
chemical
si
gnals
to
att
ract
more
phagocyt
es
Lymphocyt
es
may
also
rel
ease
ant
it
oxi
ns
that
st
ick
to
the
appr
opr
iat
e t…read more

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A
source
of
energy f
or
other
l
if
e pr
ocesses.
Somet
imes
br
ead,
bananas, r
efer
red
to
as,
a car
bohydrat
e.
sugar
and
ri
ce
cheese,
but
ter
, Fa t
s ar
e needed
to
ma ke
cel
l
me mbr
anes
and
to
insulate
margar
ine
and
oil
s ou r
bodi
es.
They al
so
contai
n i
mpor
tant
f
atsol
ubl
e
vitamins
meat,
f
ish,
eggs
and Growth
and
repair.…read more

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Def
ic
iency
diseases
incl
ude rickets,
w hi
ch af
fect
s pr
op er
gr
ow t
h of
t
he
skelet
on and i
s caused
by
i
nsuf
fi
ci
ent
vit
amin D,
and
kwashiorkor
w hi
ch causes
a swol
len
abdomen and i
s a
resul
t of
i
nsuf
fi
ci
ent
protei
n.…read more

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HDLs
are
oft
en
cal
led
`good'
chol
est
erol
because
they
hel
p t
o st
op
fat
bui
ldi
ng
up
in
the
ar
ter
ies
.
A
high
proport
ion
of
H DLs
to
LDL s
is
good
for
a
healt
hy heart
.
Mo nounsat
urat
ed and
pol
yunsatur
ated
oil
s ar
e f
ound i
n veget
abl
e oi
ls.…read more

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New
me di
ca l
dr
ug s
have t
o be t
ested
befor
e
they
can be
prescr
ibed
for
pa t
ient
s.
Th ey
are
test
ed i
n a l
aborat
ory t
o check
that
they
a r
e not
toxi
c,
and l
ater
t
he y
are
tri
all
ed usi
ng
human volunteers.
A t
t
his
point
,
an y
potent
ial
si
de
eff
ects
shou l
d sh ow
t
he mselves.…read more

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The al
cohol
in
alcohol
ic
dri
nks
such
as
w i
nes,
beer and
spi
ri
ts
is
ethanol.
I
t
is
a depr
essan t
.
Thi
s means
that
i
t
slows
d own
signal
s i
n
t
h e
nerves
and brai
n.
Small
amo unt
s o f
al
c ohol
hel
p people
to
rel
ax,
but
great
er
amou nt
s
l
ead t
o a
lack of selfcontrol.…read more

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