Virus, Apuntes de Informática. Universitat d'Andorra
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Virus, Apuntes de Informática. Universitat d'Andorra

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Asignatura: Comptabilitat de societats, Profesor: Jose Manuel Martin, Carrera: Informàtica de Gestió, Universidad: UdA
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Virus (2) Alumnes.ppt

MULTIPLICACIÓ:

! ADSORCIÓ

! PENETRACIÓ ! BIOSÍNTESI ! MADURACIÓ/MUNTATGE

! ALLIBERAMENT

•  The Phases of Viral Replication –  Attachment (adsorption) of the virus to a susceptible

host cell

–  Entry (penetration) of the virion or its nucleic acid

–  Synthesis of virus nucleic acid and protein by cell

metabolism as redirected by virus

–  Assembly of capsids and packaging of viral genomes

into new virions (maturation)

–  Release of mature virions from host cell

Bacteriophage Lytic Cycle

Lysis

" Attachment of virion to host cell is highly specific " Requires complementary receptors on the surface of a susceptible host and its

infecting virus

" Receptors on host cell carry out normal functions for cell (e.g., uptake proteins)

" Receptors include proteins, carbohydrates, glycoproteins, lipids, lipoproteins, or complexes

" The attachment of a virus to its host cell results in changes to both virus and cell

surface that facilitate penetration

RECEPTORS BACTERIANS:

Paret cel.lular:

LPS

Proteïnes

Fimbries/ Pilis

Flagels

Viral Attachment and Penetration

• Viral mechanisms to evade bacterial restriction systems – Chemical modification of viral DNA (glycosylation or methylation)

– Production of proteins that inhibit host cell restriction system

•  Many bacteria employ restriction-modification systems to evade viral infection

–  DNA destruction system; only effective against double-stranded DNA viruses

–  Restriction enzymes (restriction endonucleases) cleave DNA at specific

sequences

–  Modification of host’s own DNA at restriction enzyme recognition sites prevent cleavage of own DNA

Production of Viral Nucleic Acid and Protein

" Viral Proteins " Production follows synthesis of viral mRNA

" Early proteins

" synthesized soon after infection

" necessary for replication of virus nucleic acid

" typically act catalytically

" synthesized in smaller amounts

" Late proteins

" Synthesized later

" Include proteins of virus coat

" Typically structural components

" Synthesized in larger amounts

Cicle lític: fag virulent

Overview of the Virus Life Cycle

Eclipse? Periode latència?

The One-Step Growth Experiment

TAMANY EXPLOSIÓ

TEMPS EXPLOSIÓ (20-40’)

0,1-0,001 %

Cicle lisogènic: fag atemperat/lisogènic

#  Els bacteriòfags atemperats poden no matar després de la infecció, sinó que estableixen una relació genètica estable amb l'hoste.

#  Després de l'entrada en la cèl·lula hoste, entren en lisogènia: els seus gens no s'expressen, i el genoma del virus (anomenat "profag”) es replica conjuntament amb el genoma de l'hoste (ja que normalment s'integra en ell).

#  La simple presència del genoma víric no fa mal a la cèl·lula hoste, que es denomina en aquest estat "cèl·lula lisògenica".

#  En determinades condicions, els virus lisogénics poden revertir a la via lítica i començar a produir virions.

Cicle lisogènic $ Lisogènia $ Fag lisogènic o atemperat (phages able to establish lysogeny)

$ Cèl.lula lisogènica (infected bacterial host) $ PROFAG (integrated phage genome) Ex. Fag Lambda /E. coli

Conseqüències: 1. Immunitat enfront de fags similars

2. Canvi propietats cel.lulars / Conversió fàgica

Corynebacterium diphteriae Salmonella sp.

3. Intercanvi genètic: TRANSDUCCIÓ

Lysogeny (Temperate Phage)

Virus d’eucariotes

Reproduction of Animal Viruses •  adsorption •  penetration and uncoating •  replication of virus nucleic acids •  synthesis and assembly of virions •  virion release

2. penetració

Fussió

Endocitosi

http://www.youtube.com/watch?v=NKoZfHLQu5M

Virus herpes simplex

Mechansim_for_releasing_enveloped_virions http://www.youtube.com/watch?v=rfCTCV_0hu0

Biosynthesis Cytoplasm In nucleus or cytoplasm Assembly of virions (depend on the viruses)

VIH

Virus d’animals:

Mechanisms of host cell damage and cell death •  inhibition of host DNA, RNA, and protein synthesis •  lysosome damage

–  causes release of hydrolytic enzymes into cell •  alteration of plasma membrane

–  can lead to attack of host cell by immune system –  can lead to cell fusion, forming syncytium

•  toxicity from high concentrations of viral proteins •  formation of inclusion bodies •  chromosomal disruptions •  transformation of host cell into malignant cell

•  functional changes

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