Study Notes on Viruses and Pathogenic Organisms

Characteristics of Living Organisms

  • Organisms must exhibit the following seven characteristics to be considered living:
    • RIVA or DNA: Living organisms exclusively have either ribonucleic acid (RIVA) or deoxyribonucleic acid (DNA), but not both.
    • Reproduction: Living organisms have the ability to reproduce, though some pathogens like viruses cannot reproduce independently and require a host cell.

Pathogenic Organisms

  • Pathogenic Definition: Organisms that cause disease in their hosts are classified as pathogenic. Viruses are considered pathogenic due to their nature of invading host cells.

Virus Structure and Life Cycle

  • Virus Structure: A typical virus consists of a protein coat known as a capsid that encases its genetic material. The structure varies, with types including spherical, thread-like, and bacteriophage forms.

  • Bacteriophage: A specific type of virus that infects bacterial cells.

  • Life Cycle Phases of a Virus:

    1. Attachment: The virus attaches itself to a host cell.
    2. Entry: The virus inserts its genetic material (either RIVA or DNA) into the host cell.
    3. Replication: Once inside the host, the virus's genetic material is replicated along with the necessary components for new virus particles.
    4. Assembly: The newly replicated parts of the virus are assembled into complete viral particles.
    5. Lysis: The host cell undergoes lysis, meaning it bursts and releases new viruses into the surrounding environment (the body), which can go on to infect more cells.

Vaccines

  • Definition: Vaccines are biological preparations that provide active acquired immunity to specific infectious diseases.
  • How Vaccines Work: Vaccines typically contain small, dead fragments of a pathogen (such as a virus), which stimulate the immune system to produce antibodies. This preparation enables the immune system to recognize and combat the actual virus in future encounters.