Viruses 08/01/bacteria-and-viruses-combo- 2.ppt

STRUCTURE Nonliving Nonliving Composed of a nucleic acid and a protein coat Composed of a nucleic acid and a protein coat Cause many diseases Cause many diseases Virology – Study of Viruses Virology – Study of Viruses Comparison of Viruses and Cells below Comparison of Viruses and Cells below Char. Of Life VirusCell GrowthNoYes HomeostasisNoYes MetabolismNoYes MutationYesYes Nucleic acid DNA or RNA DNA Reproduction Only within host cell Independently by cell division Structure Nucleic acid core, protein covering, some have envelope Cytoplasm, cell membrane, etc..

Nucleic acid (DNA or RNA) Protein Coat ( capsid) Structure of a Virus

Characteristics of Viruses 2 essential features 1. Nucleic Acid 1. Nucleic Acid May be DNA or RNA May be DNA or RNA Helical, closed loop, or long strand Helical, closed loop, or long strand 2. Protein Coat – called CAPSID 2. Protein Coat – called CAPSID Some have ENVELOPE Some have ENVELOPE Ex. Influenza, chickepox, herpes simplex, HIV Ex. Influenza, chickepox, herpes simplex, HIV VIRAL SHAPE VIRAL SHAPE Icosahedron – 20 triangular faces Icosahedron – 20 triangular faces Ex.) herpes, chickenpox, polio Ex.) herpes, chickenpox, polio Helix – Coiled spring Helix – Coiled spring EX.)Rabies, measles, tobacco mosaic EX.)Rabies, measles, tobacco mosaic

Grouping Viruses Grouped according to: Grouped according to: Presence of capsid and envelope – shape Presence of capsid and envelope – shape RNA or DNA, single or double stranded – structure RNA or DNA, single or double stranded – structure Viral Group Nucleic Acid Shape and Structure Example Papovaviruses DNA Icosahedral, non-env. Warts, cancer Adenoviruses DNA Icosahedral, non-env. Resp. & intestinal infections Herpesviruses DNA Icosahedral, enveloped Herpes simplex, chicken pox, mono, shingles Poxviruses DNA Complex brick, enveloped Small pox, cow pox Picornaviruses RNA Icosahedral, non-env. Polio, hepatitis, cancer Myxoviruses RNA Helical, enveloped Influenza A, B, C Rhabdoviruses RNA Helical, enveloped Rabies Retroviruses RNA Icosahedral, enveloped AIDS, cancer

Other Grouping of Viruses Viroids- The smallest known particle that can replicate. Viroids- The smallest known particle that can replicate. Disrupt plant cell metabolism Disrupt plant cell metabolism Can destroy entire crops Can destroy entire crops Prions – Abnormal forms of proteins that clump together inside cells. Prions – Abnormal forms of proteins that clump together inside cells. Clumping eventually kills the cell Clumping eventually kills the cell Examples Examples Scrapie – in sheep Scrapie – in sheep Mad Cow Disease Mad Cow Disease

Viral Replication Can replicate only by invading host cell and using its enzyme and organelles. Can replicate only by invading host cell and using its enzyme and organelles. Bacteriophage – viruses that infect bacteria Bacteriophage – viruses that infect bacteria Used to study viruses Used to study viruses

Lytic Cycle of Virus Replication Lytic Cycle Lytic Cycle Viral genome is released into the host cell Viral genome is released into the host cell Replication follows immediately Replication follows immediately Cellular components used to make new viruses Cellular components used to make new viruses Viral enzyme kills cell. Viral enzyme kills cell. Play animation Play animation Play animation Play animation

Lysogenic Cycle of Virus Replication Nucleic acid of virus becomes part of the host cell’s chromosome Nucleic acid of virus becomes part of the host cell’s chromosome Nucleic acid remains in the cell in this form for many generations Nucleic acid remains in the cell in this form for many generations HIV follows this pattern HIV follows this pattern HIV infects WBC and remains as proviruses HIV infects WBC and remains as proviruses As immune system fails, opportunistic infections occur = AIDS As immune system fails, opportunistic infections occur = AIDS Play animation Play animation Play animation Play animation Play animation Play animation Play animation Play animation

Viruses and Human Disease Control and Prevention of spread. Control and Prevention of spread. Vaccination & Antiviral drugs Vaccination & Antiviral drugs Ex.) chickenpox vaccine, AZT, Acyclovir, protease inhibitors. Ex.) chickenpox vaccine, AZT, Acyclovir, protease inhibitors. Emerging Viruses – exist in isolated habitats Emerging Viruses – exist in isolated habitats Do not usually infect humans unless environmental conditions favor contact. Do not usually infect humans unless environmental conditions favor contact. Several viruses are now linked to cancers such as leukemia, liver cancer, Burkitt’s lymphoma, cervical cancer. Several viruses are now linked to cancers such as leukemia, liver cancer, Burkitt’s lymphoma, cervical cancer.

PAPOVAVIRUSES

ADENOVIRUSES

HERPESVIRUSES

POXVIRUSES

PICORNAVIRUSES

After polio infections, the killer T-cell have destroyed the motor neurons that are producing the virus. The result is a loss of muscle control including the diaphragm. The iron lung changes the pressure to pump air in and out of the lungs.

MYXOVIRUSES

RHABDOVIRUSES

RETROVIRUSES

Research the following viruses Viral Group Papovaviruses Adenoviruses Herpesviruses Poxviruses Picornaviruses Myxoviruses Rhabdoviruses Retroviruses

Look at how the virus infects pages/Chap11.html pages/Chap11.html