Bi
ology111(
Biol
ogyI
)sol
vedt
utor
ial
1)Inwhatwayswouldyourefertouseacompoundl
i
ghtmi
croscopet
han
tr
ansmissi
onelect
roni
cmicroscope?
Whenstudyi
ngli
vi
ngcell
s.Anelect
ronmi
croscopecanonl
ybeusedon
deadspeci
mens.wher
eas,ali
ghtcanbeusedondeadorali
vespeci
mens.
Expl
anat
ion:
Onebi gadv ant ageofl i
ghtmi cr
oscopesistheabili
tytoobser veli
vingcel
ls.
Itispossiblet oobser veawi derangeofbiologi
calactivi
ty,suchast he
uptakeoff ood, cell
divisi
onandmov ement .Addit
ionally
,itispossibl
eto
usei n-vi
vost aini ngtechniquestoobserv
et heuptakeofcol oredpigments
byt hecells.Thesepr ocessescannotbeobser vedinr ealti
meusi ng
electronmi cr oscopes, asthespecimenhast obefixed,andcompl etel
y
dehy drat
ed( andi stheref
oredead).
El
ectr
onsinelect
roni
cmicroscopehaveshortwav
elengt
hs(shor
tert
han
phot
ons)thatmovebesti
nav acuum,
soliv
ingcel
lscannotbevi
ewedwit
h
anel
ectr
onsmi cr
oscope.
2)I
n1609Gal
il
eoinv
entedthel
i
ghtmicr
oscope,buti
twasRober
tHooke
i
n1665whowasthefi
rstt
oobserv
ecell
s.Expl
ain
Let
sstartbydefi
ningwhatani
nvent
ioni
sandwhatandi
scov
eryi
sfor
bet
terunderst
andi
ng.
Adiscov eryi
srecogni
zi
ngsomet hi
ngthatalr
eadyexistsforthefi
rstti
me,
thatnobodyhasf oundbefor
e,e.g.howRober tHookediscoveredor
observet hecel
l
s.Aninventi
oniscr eat
ingsomethi
ngt otal
lynewwi t
hone'
s
owni deasanddev el
opment...
.e.g.howGalil
eoinventedthelight
microscope.
, Expl
anat
ion
Rober
tHookegeneral
lyr
ecei
vemuchofthecr
editf
orear
lyadvancesi
n
micr
oscopy
,nei
thercancl
aimtobet
heinvent
orofthemi
croscope.
Mor
eExpl
anat
ion:
In1609,whi
let
ryi
ngtodevel
ophistel
escope,Gali
l
eoGal i
l
eiusedlenses
withashort
erf
ocall
engthtot
urnhistel
escopeintoamicroscopethat
couldbeusedt
omagni f
ysmallobj
ect
s.Thismicroscopeusedtwol enses,
thesebei
ngabi-
convexobj
ecti
veaswellasabi-concaveeyepi
ece.
Alt
houghGali
leoalsodev el
opedanothermi
croscopein1624thatused
thr
eebi-
convexlenses,i
tdidnotprov
idemoremagni f
icat
ionthathi
searl
i
er
i
nventi
on.Gali
leo'
smi cr
oscopeprovi
dedamagni fi
cat
ionofabout30x.
Rober
tHooke(
1665)
I
n1665, RobertHooke,anEngl i
shnat ur
alphil
osopherandphy si
cist
publ
ishedt he"
Mi cr
ogr
aphi a"i
nwhi chhewr otedownaccountsofhi s
observati
onsusingami croscope.Usingapr i
miti
vemicroscope,Hooke
wasabl etoobserveawi derangeofobjectsincl
udingfl
easandcor ks.
Here,hewasabl etoobser v
esmal lhair
sont hefl
eaaswel l
asporesont he
cork(whichhereferr
edt oascells)
.Howev er
, whatHookedidnotreal
izeat
theti
mewast hathehadj ustdi
scov er
edplantcell
s.Hooke'
smi cr
oscope
wasasi ngl
elensmi croscopethatwasi l
lumi
natedbyacandl e.
3)Noonehasdisput
edcellt
heor
ytodat
e.Butwhatdoy
out
hinkar
esome
ofli
mit
ati
onsofcell
theor
y?
St
ruct
ureofv
irus-Schl
eidenandSchwanncoul
dnotexpl
aint
hest
ruct
ure
ology111(
Biol
ogyI
)sol
vedt
utor
ial
1)Inwhatwayswouldyourefertouseacompoundl
i
ghtmi
croscopet
han
tr
ansmissi
onelect
roni
cmicroscope?
Whenstudyi
ngli
vi
ngcell
s.Anelect
ronmi
croscopecanonl
ybeusedon
deadspeci
mens.wher
eas,ali
ghtcanbeusedondeadorali
vespeci
mens.
Expl
anat
ion:
Onebi gadv ant ageofl i
ghtmi cr
oscopesistheabili
tytoobser veli
vingcel
ls.
Itispossiblet oobser veawi derangeofbiologi
calactivi
ty,suchast he
uptakeoff ood, cell
divisi
onandmov ement .Addit
ionally
,itispossibl
eto
usei n-vi
vost aini ngtechniquestoobserv
et heuptakeofcol oredpigments
byt hecells.Thesepr ocessescannotbeobser vedinr ealti
meusi ng
electronmi cr oscopes, asthespecimenhast obefixed,andcompl etel
y
dehy drat
ed( andi stheref
oredead).
El
ectr
onsinelect
roni
cmicroscopehaveshortwav
elengt
hs(shor
tert
han
phot
ons)thatmovebesti
nav acuum,
soliv
ingcel
lscannotbevi
ewedwit
h
anel
ectr
onsmi cr
oscope.
2)I
n1609Gal
il
eoinv
entedthel
i
ghtmicr
oscope,buti
twasRober
tHooke
i
n1665whowasthefi
rstt
oobserv
ecell
s.Expl
ain
Let
sstartbydefi
ningwhatani
nvent
ioni
sandwhatandi
scov
eryi
sfor
bet
terunderst
andi
ng.
Adiscov eryi
srecogni
zi
ngsomet hi
ngthatalr
eadyexistsforthefi
rstti
me,
thatnobodyhasf oundbefor
e,e.g.howRober tHookediscoveredor
observet hecel
l
s.Aninventi
oniscr eat
ingsomethi
ngt otal
lynewwi t
hone'
s
owni deasanddev el
opment...
.e.g.howGalil
eoinventedthelight
microscope.
, Expl
anat
ion
Rober
tHookegeneral
lyr
ecei
vemuchofthecr
editf
orear
lyadvancesi
n
micr
oscopy
,nei
thercancl
aimtobet
heinvent
orofthemi
croscope.
Mor
eExpl
anat
ion:
In1609,whi
let
ryi
ngtodevel
ophistel
escope,Gali
l
eoGal i
l
eiusedlenses
withashort
erf
ocall
engthtot
urnhistel
escopeintoamicroscopethat
couldbeusedt
omagni f
ysmallobj
ect
s.Thismicroscopeusedtwol enses,
thesebei
ngabi-
convexobj
ecti
veaswellasabi-concaveeyepi
ece.
Alt
houghGali
leoalsodev el
opedanothermi
croscopein1624thatused
thr
eebi-
convexlenses,i
tdidnotprov
idemoremagni f
icat
ionthathi
searl
i
er
i
nventi
on.Gali
leo'
smi cr
oscopeprovi
dedamagni fi
cat
ionofabout30x.
Rober
tHooke(
1665)
I
n1665, RobertHooke,anEngl i
shnat ur
alphil
osopherandphy si
cist
publ
ishedt he"
Mi cr
ogr
aphi a"i
nwhi chhewr otedownaccountsofhi s
observati
onsusingami croscope.Usingapr i
miti
vemicroscope,Hooke
wasabl etoobserveawi derangeofobjectsincl
udingfl
easandcor ks.
Here,hewasabl etoobser v
esmal lhair
sont hefl
eaaswel l
asporesont he
cork(whichhereferr
edt oascells)
.Howev er
, whatHookedidnotreal
izeat
theti
mewast hathehadj ustdi
scov er
edplantcell
s.Hooke'
smi cr
oscope
wasasi ngl
elensmi croscopethatwasi l
lumi
natedbyacandl e.
3)Noonehasdisput
edcellt
heor
ytodat
e.Butwhatdoy
out
hinkar
esome
ofli
mit
ati
onsofcell
theor
y?
St
ruct
ureofv
irus-Schl
eidenandSchwanncoul
dnotexpl
aint
hest
ruct
ure
