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Microbiology: Viruses and Prions

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이 집합의 용어 (20)

  • What are viruses?
    Obligate intracellular parasites that require a host cell to reproduce; they infect bacteria, protozoa, fungi, algae, plants, and animals.
  • Do viruses fulfill the characteristics of life independently?
    No, viruses do not independently fulfill the characteristics of life and are not cells.
  • What is the basic structure of a virus?
    A protein shell (capsid) surrounding a nucleic acid core, which can be either DNA or RNA, but not both.
  • What is a nucleocapsid?
    The capsid together with the nucleic acid inside the virus.
  • What is the difference between naked and enveloped viruses?
    Naked viruses consist only of a nucleocapsid; enveloped viruses have an external membrane derived from the host cell membrane.
  • What are viral spikes and their function?
    Protein projections on the virus surface that allow viruses to dock with host cells.
  • What are the two basic viral capsid shapes?
    Icosahedral (20 triangular faces, very stable) and helical (rod-shaped, all animal helical viruses are enveloped).
  • What types of nucleic acids can viruses have?
    Viruses can have single-stranded or double-stranded DNA or RNA, but never both DNA and RNA simultaneously.
  • What is a retrovirus?
    An RNA virus that carries enzymes to create DNA from its RNA for integration into the host genome.
  • What is the genome size of viruses compared to cells?
    Viral genomes are much smaller; for example, hepatitis B virus has only four genes.
  • What is a persistent viral infection?
    A state where the virus remains in the host cell without immediate lysis, potentially lasting for the host's life.
  • What is a chronic latent viral infection?
    A viral infection that periodically reactivates under stimuli, such as herpes simplex and herpes zoster viruses.
  • How do viruses contribute to cancer?
    Some viruses carry oncogenes or produce proteins that disrupt growth regulation, leading to cancer.
  • Name some oncoviruses and the cancers they cause.
    Papillomaviruses (cervical cancer), herpesviruses, hepatitis B virus (liver cancer), and human T-lymphotropic virus (leukemia, lymphoma).
  • What is a bacteriophage?
    A virus that infects bacteria, often making the bacteria more pathogenic to humans.
  • How are animal viruses cultivated for study?
    Using in vivo methods (lab animals, embryonic tissues) or in vitro cell or tissue cultures.
  • What are plaques in viral culture?
    Clear areas on a cell sheet where virus-infected cells have been destroyed, indicating viral growth.
  • What are prions?
    Infectious proteins with an unclear mode of infection, causing diseases like Creutzfeldt-Jakob and mad cow disease.
  • Why are antibiotics ineffective against viral infections?
    Because antibiotics target bacterial processes, and viruses lack the metabolic machinery targeted by antibiotics.
  • What is the size range of viruses?
    Viruses range from about 20 nm (parvoviruses) to 150 nm (herpes simplex virus) and require electron microscopy to be seen.