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Viruses

Explore the intricate world of viruses, learning about their composition, replication cycles like lytic and lysogenic, virulence, and host immune responses. Discover how viruses impact the delicate balance of life sciences.

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Viruses

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  1. Viruses Advanced Life Science Mr Taylor Rainier Jr/Sr High School

  2. Viruses • Made of two parts • Nucleic acid • Protein coat/capsid • Nucleic acid • Can be either DNA or RNA • Shapes: single strand, double strand, linear, or circular

  3. Viruses • Made of two parts • Nucleic acid • Protein coat/capsid • Protein coat • Also called the capsid • Many different shapes • Often classified by their shape

  4. Viruses • Reproductive Cycles (2 types used) 1. Lytic cycle a. Adsorption: Binding sites on virus and host cell match, a chemical bond is created b. Entry: Enzymes break down the cell wall and/or cell membrane and nucleic acid enters the cell c. Replication: With DNA viruses the DNA breaks into the host’s chromosomes and begins to make mRNA strands and replicates itself

  5. Viruses • Reproductive Cycles (2 types used) 1. Lytic cycle a. Adsorption: Binding sites on virus and host cell match, a chemical bond is created b. Entry: Enzymes break down the cell wall and/or cell membrane and nucleic acid enters the cell c. Replication: With RNA viruses a mRNA strand is made and new viral proteins are constructed. The RNA also replicates itself.

  6. Viruses 1. Lytic cycle (continued) d. Assembly: The newly constructed pieces of virus are assembled together to create a virion. e. Release: An enzyme breaks down the cell wall and/or membrane rupturing the cell and releasing the new virus particles. This rupturing of the cell is called lysing

  7. Viruses • Reproduction 2. Lysogenic cycle Occurs with DNA viruses. The first stages are the same (Adsorption, Entry), but the viral DNA stays in the host’s DNA and is replicated whenever the host cell divides. This is called a prophage. At some point and with the correct stimulus, the prophage will become active and complete the cycle (Replication, Assembly, Release)

  8. Viral Infections • Virulence • The ability to cause disease is virulence. • Virulence can range from almost none (inapparent infections) to deadly. • Some viruses can cause tumors (cancer) • Most are species specific and organ/organ system specific.

  9. Host Response • Skin/mucus membranes • First line of host defense • A physical barrier • Entry into the body stimulates an antigen/antibody response • An antigen is anything, usually a protein, that is foreign to the host. • An antibody is created specifically to “match up” with a particular antigen.

  10. Host Response • If an organism produces its own antibodies, this is called active immunity. • Vaccinations • If the organism receives the antibodies from another organism, this is called passive immunity. • Gamma globulins • Interferon: works against many viruses, but is species specific.

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