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Understanding Viruses: Structure, Types, and Impact on Human Health

Explore the fascinating world of viruses, non-living particles that can only replicate within living cells. Discover their structure, including the protective protein coat called the capsid, and how they trick host cells into allowing their entry. Delve into different types of viral infections: lytic and lysogenic, each with unique mechanisms of replication. Additionally, learn why vaccines for viruses like influenza need annual updates due to rapid mutations in RNA viruses, including HIV. This informative overview highlights the critical role viruses play in disease and the necessity of vaccination.

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Understanding Viruses: Structure, Types, and Impact on Human Health

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  1. Chapter 19-2 Notes

  2. Definition of viruses: • Non-living (?) disease-causing particles • Composed of DNA or RNA surrounded by a protein coat. • Can only reproduce wheninside other living cells.

  3. Structure of a virus Capsid • Made up of proteins (receptors) • Its purpose is to “trick” the cell into letting it inside the cell membrane. http://www.genetherapynet.com/viral-vectors.html (2:24 minutes, clip 3)

  4. Examples of structures Influenza virus Bacteriophage Tobacco Mosaic Virus

  5. Bacteriophage • A virus that infects a bacterium cell.

  6. Types of Viral Infection

  7. Lytic Infection • Both lytic and lysogenic infections begin with the virus attaching to the cell and injecting its DNA. • The viral DNA over-powers the cell’s DNA and causes the cell to make new viruses instead of doing its normal functions. • The new viruses release an enzyme to dissolve the cell membrane and exit the cell, free to infect new cells.

  8. Lysogenic Infection • Instead of immediately causing the cell to reproduce the viruses and bursting open the cell, the viral DNA (called a prophage) is inserted into the cell’s DNA. • Both pieces of DNA (the cell’s and the virus’s) are replicated when the cell reproduces for many generations. • The viral DNA is removed from the cell’s DNA and is free to begin lytic infection.

  9. Which type of infection is this?

  10. Importance of Viruses 3:23 minutes, Clip 6: Influenze vaccine If we have a vaccine to the flu, why do we need to get a new shot each year? 3:04 minutes, Clip 7: RNA viruses

  11. Retroviruses/RNA viruses • Viruses that contain RNA instead of DNA • Are not “checked” for mutations like DNA viruses are, so mutate often and quickly • Remain dormant for long periods of time • Examples: Flu, HIV

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