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VIRUS MEANS
“POISON”!
MADE OFPROTEIN ANDNUCLEIC ACID(EITHER DNA or
RNA)
Protein part isthe CAPSID
NA isinsidecapsid
Living or Not?They have
genetic material & structural proteins
BUT:
No RibosomesNo Organelles
No NucleusCan’t Use Energy
AND:
They CannotReproduce
on their own
SO:They are
NON-LIVING!
They arereferred to as
ObligateIntracellular
Parasites
They need aHOST CELLin order toreplicate.
They can beclassified3 Ways:
INTERESTINGSHAPES!
Polyhedron,Helical, Complex
Some are“enveloped”with a membrane-like structure
Their nucleicacid type:
Either DNA orRNA virus
DNA virus:DNA is inserted into
cell, then protein
synthesis using virus mRNA
OR, Virus DNAjoins host cell
DNA and replicates withhost cell DNA
RNA Virus:virus RNA isinserted into
host cell,makesproteins directly
OR, RNA retrovirus:
DNA, made by reverse
transcription, joins host DNA,
followedby protein synthesis
Classifiedby whether or not the virus
isdisease-causing
Virus can be“virulent”--causesdisease right away
(like a cold orflu)
If virulent,they undergo
theLYTIC CYCLE
Lytic Cycle:1)
Adsorption:virus
attachesto host cell
2) Entry:virus NA is
injected intohost cell
3) Replication:Host cell startsmaking virus
parts
4) Assembly:virus parts
getput together
5) Release:host cell gets so
full of new virusesthat it bursts,
releasing viruses
Virus can be“temperate”--waits
to cause diseaselater
(like HIV)
a) If temperate,virus goes intothe LYSOGENIC
CYCLE
b) LYSOGENICCYCLE:
Starts like lyticcycle with
adsorption & entry
c) Then,Attachment:
virus DNA joinswith host DNA
d) Replication:Host cell
undergoesreplication; virusDNA gets copied
e) Activation:something
triggers thevirus to becomevirulent (lytic)
Then,it startsthe LYTIC
CYCLE andcauses
infection (disease).
How are virusesspread?
Bodily fluidsThrough air, waterDirect contact
What is smaller than a virus?
Viroid--NA onlycause plant
diseases
Prion--smallstrand of aminoacids; mammal diseases like CWD or Mad Cow disease
How could youprevent viralinfections?
VaccinationsWash hands!Cover your mouth when sneezing or coughing!Safe sex!