Lecture Notes: Viruses and the Common Cold

The Common Cold

• Symptoms: Sneezing, coughing, feeling unwell.
• Treatment: Medications can alleviate symptoms but do not cure the cold.
• Cause: Caused by a virus, not treatable with antibiotics.

Understanding Viruses

• Nature: Viruses are not cells and are not classified as living organisms.
  • Debate: Some debate about whether they are non-living.
• Structure:
  • Smaller than cells, require electron microscopes for viewing.
  • Come in various shapes (e.g., bacteriophage).
  • Contain genetic material (DNA or RNA).
  • Surrounded by a protein coat (capsid).
  • May have additional structures like enzymes or an outer envelope.

Virus Replication

• Host Dependency: Viruses need a host to replicate, using the host cell's machinery.
• Lytic Cycle:
  • Virus attaches and injects its genetic material into the host cell.
  • Host cell makes copies of the virus, leading to the cell membrane's rupture.
  • Viral copies infect other cells.
• Lysogenic Cycle:
  • Viral genetic material integrates with host's DNA.
  • Replicated with host cells until triggered to enter the lytic cycle.
  • Trigger can be chemical or environmental.

Specific Viruses: HIV

• Characteristics:
  • Targets CD4 glycoproteins on helper T cells.
  • Weakens immune system, making the host vulnerable.
• Treatment:
  • Medications slow replication.
  • Research focuses on preventing viral attachment.
• Challenge: Virus mutations can hinder treatment effectiveness.

Positive Aspects of Viruses

• Gene Therapy: Some viruses are used in gene therapy.
• Biological Control:
  • Viruses can target pest insects as an alternative to chemical pesticides.
  • Example: Nuclear polyhidrosis virus.
• Considerations: Potential ecological consequences of viral pesticides.

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Note: Always stay curious and continue exploring topics beyond the basics.