Chapter 12 structure of viruses revised

Living characteristics of viruses in living host cells.. The Size and Morphology of Selected Viruses Copyright © The McGraw-Hill Companies, Inc.. Permission required for reproduction or

Microbiology: A Clinical Approach © Garland Science

OVERVIEW

General features of Viruses

and nonliving characteristics

1 Living characteristics of viruses

in living host cells

b They can mutate

…General features of Viruses

2 Nonliving characteristics of viruses

cytoplasm or cellular organelles

and must replicate using the host cell's

metabolic machinery

 Virus particles contains either DNA or RNA (not both)

protein shell (capsid)

envelope surrounding the particle

…General features of Viruses

…General Properties of viruses

enclosed in coat of protein

nor carry out cell division as procaryotes and eucaryotes do

The Size and Morphology of

Selected Viruses

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Generalized Structure of Viruses

…Generalized Structure of Viruses

The Structure of Viruses

composed of nucleic acid (DNA or RNA) and

others have additional components

VIRAL ENVELOPES

• Many viruses that infect humans and

other animals are enveloped.

• Envelopes form when viral glycoproteins and oligosaccharides associate with the plasma membrane of the host cell.

• All envelopes have a phospholipid

bilayer.

ENVELOPE GLYCOPROTEINS

bilayer

membrane proteins called spanners.

outside of the virion

which serve as protein coat of virus

transfer between host cells

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VIRUS CLASSIFICATION

Helical Capsids-Tobacco Mosaic

Virus

walls

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Influenza Virus – an Enveloped

Virus with a Helical Nucleocapsid

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HELICAL VIRUSES

ICOSAHEDRAL VIRUSES

that make up the capsid

Icosahedral capsids

THE INFECTION CYCLE

bacteriophages (bacterial viruses)

lysogenic

LYTIC VERSUS LYSOGENIC INFECTION

virions and bursts

• Lysogenic infections are also known as latent infections

into the host cell’s DNA

period

LYTIC VERSUS LYSOGENIC INFECTION

Receptor sites:

viruses attach

acids, etc

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proteins and receptor.

Entry into the Host

their nucleic acid into host

with the genome still enclosed

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30

Viruslike Agents

 Prions

31

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 Homework: Important group of RNA viruses

Viral Diseases (Next chapter)

A Influenza

B Diseases Caused by the Herpes Family

C Viral Hepatitis

D Human Immunodeficiency Virus

E Miscellaneous Viral Diseases