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Topic 2 viruses and cell division A level Biology B Edexcel notes

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Providing an in-depth, complete and well-written notes according to the A level Biology B Edexcel specification. Notes contain information on viruses, cell division: mitosis and meiosis

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tCnhal
Jptsexual reprelahon tphase, ritosis, cytolineie

Viruses - Bio 9/012h
L7 to Make lmore proteins - neadsị a host (oell achinery))
b hey are non-Cellular inhechous parhles that sruddle the boundury
behteen iving Inon-living'
and
t have no ceu wall.
-7Non eliving shuctures which consist of acid) (DNA or RNA),enclosed
a nycleic
in arotechveproein Cocat called capsīd) and Somehines (overed with
ipr bilyer) envelope
rror geometrie shrucre-
Struchre of viruses are sirple (smaer Fhan prolaryohe cels)

receptors.
(not always bind to hosh cells
present).


enuelope- dovble or Single stranded, DNÍA
lipid derived or KNA
from nost cell
Membrunes



Capsid-
protein coat Cupsorere repeahing protein unit thatmales up
(some have). the protein Coat.


Classifying virUes

• Viruses are clessıhieed by shuchure in aucleic ccid type
Viuses are Classifred b their (Genome) and heie mode replicetion.
Virual qeneh nuteriul can be DNA or RNA,he nvcleic acId sonehies
double shendtaaek sandee andsornehires Single-
L> DNA viruses qeneheal Material is (DNA)viral DNA acts directy as
For both new virual DINA and for the CmhA needecd
indue Synthesš o iralproteins Smellpox virvs
adenovirses-ey : lambda) phage
g
>RNA virvses= 701 of vinUses USe RNA as their eteril and
ere rore uely to utate han D'A iruses. ajori ky of
nNA irusescontain a singl. srand of vA anot ure
hnown as (SSRNA viruse
Posihive ssRNA vivses huvet that directlyatslas atnwÀ
and be anslatee at the bosores. eq18baccoMosaizvirsU
L>Usel to mandproteins L> posihve SSRNA
) KNAretrovivsesa peeial yee of KA virys tas a peten Capad) onc
a (pd enaloee).Single shand of viqal KNA directs the
RNA DNA spećial tnzyme called reverse ranscripas
males PNA Moleculescorrespond o the Vìral genom
brey HIlV
Viruses atach to their host cels proteins Unown a
uirus attachment parheles that haryet proteins in the host
cell Surface Membrae. heyresponelo parhular molecules ofthe
(host cell surtace,)) (uinuses are specitc in the h'ssve mey att

,Reprelvchon in viruse s
previruS into the
Lo latency- thelysogenie porngDA the formo a be
*ly sogenie vises ns er DNA viral DINĄ
BNA of the host cell which enables the shay
Carn
hest cell - Provinus
rgplbcatecl by cell division of the which ahibit
dormant i the vius prduces represser proteins
the hran seriphon of Hhe provins
b Lythie viruses host cell, the
the
they insert pNA Z RNA into the cyplasr
indepn denty of the host cell genome.
vi7al genome is replicated
leads to lysis of the host, celltowhen a
numbeof
lurgyecells
numbe oA
Viruses are aSsembledl and ready
ready infect More cells

when lysogenie host cels damagecl or the immUne systen
become
becomes weak, the dormant 'ruses cun enter the uhe3e
pathway
vialnfeck Cacls leads lysis of the cell and the spreccd


-> Vvitvses are non - liing , antivitals must wor. Vivs replicahon Vinses
by inhibihing
cun be dihclt to reat one an infechot has otzurted, the focus ot
disease conhol shovld be on
pevenhing he spreud
b> ldea exemplhed by the (2014 ebola outbreau in
west Airica-)> viral ansmission,immune response,developnent of
Were neded gicMy heatments.
Ethical ipliahons wing,no ing, untested drvg > vical eplicCahon
Consen
Unlnewn sule ehects
* May net be 4s etfeahie as the currenthy auphed treatreat

, 2.2: Viruses

k> vinses cassiied into specitic groyps based an its genehe mạtialt.

bacteria basel on genchzal maternial t proteins. Vinses are not hnn9
tdon't belong in three daraias of lite).

- Vinses, dlassihed in heir ouwn seperate cassaicahan syshen Balh
Hore dassihiiahassysfem - ivided iato 6segerateclesseshesedon
qenehe nahend

classihtd basel on qenehe material t Ode of rephiaton
Lo DNA, RNA lthe way i% gphiated)
DNA Cd.s) (s5) [Single shand, dovbie Lo based on type
RNA (s$)» cds) standed. afgeneht matnial
can haveogposite strands.

D aenehe Mateniul < DNA,viral DNA atb as a terplate for nial
DNA R walmNA.
Viral proeins

Virus

iransnphion
DNA
Used o new vinses.
MAMe RND
protins

vial rNA neded to ale viml pteins.

b>Eg. 2 llarmbda) phage vinus = yirvs intecbs bacternia
ko double shanded NA ins.

O henehic Matenial is RNA , dassitied auordling to posiive or ngave
nggahve
Sense RNA

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