Key Questions:
Differences between viruses and bacteria?
Are all bacteria harmful?
Should antibiotics be taken for a cold?
Best practices to avoid getting sick?
Definition: The study of microscopic organisms including:
Viruses
Bacteria (Archaea and Eubacteria)
Protists (e.g., paramecium)
Some Fungi (e.g., yeast)
Characteristics:
Non-cellular particles
Composed of genetic material (either DNA or RNA) and protein
Ability to invade all types of life forms: animals, plants, and microorganisms (e.g., eubacteria, archaea)
Examples of viruses: HIV, Herpes, Influenza
Lack cellular structures like:
Cell membrane
Membrane-bound organelles (nucleus, mitochondria, Golgi apparatus)
Inactivity outside a host cell
Viruses are entirely inert until they invade a host cell
Capsid
Protein coat providing protection for genetic material
Genetic Material (DNA/RNA)
Instructions for replication within the host cell
Enzymes
Facilitate viral entry and takeover of the host cell
Specific Envelope Proteins
Allow virus attachment to specific host cells, e.g., bacteriophages have tail fibers for this purpose
Definition: Involves takeover of the host cell to produce new viruses.
Attachment: Virus connects to host cell surface.
Entry: Virus injects genetic material, using an enzyme to weaken entry point.
Replication & Assembly: Viral genetic information commandeers host machinery to create virus components.
Lysis: Host cell bursts, releasing new viruses and continuing the cycle.
Virulence: Indicates the infectious capacity of a virus based on its ability to complete the lytic cycle.
Definition: Host cell remains unaltered, viral DNA integrates into host DNA (forming a Prophage).
Integration: Viral genetic material merges into the host DNA, generally non-destructive.
Cell Multiplication: Host cell divides normally, copying viral DNA alongside.
Latency: Prophage remains inactive while the host cell continues to function.
Activation: Triggers (like stress) may lead prophage to exit and switch to lytic cycle.
Characteristics of Life:
Growth: NO for viruses, YES for cells.
Homeostasis: NO for viruses, YES for cells
Metabolism: NO for viruses, YES for cells.
Genetic Material: BOTH have DNA/RNA
Reproduction: Only with a host for viruses, Cell division for cells
Conclusion: Viruses are considered NON-LIVING.
Examples of viral diseases include:
Herpes simplex
Chicken pox
HIV
Hepatitis
Viral Specificity: Certain viruses infect specific hosts only.
Prevents virus entry:
Skin (barrier unless breached)
Mucous membranes in respiratory tract (trap pathogens)
Hydrochloric acid in stomach (destroys viruses)
Immune response:
White blood cells (WBCs) produced (lymphocytes, phagocytes)
Phagocytes engulf and destroy intruders.
Produced by lymphocytes: Antibodies target specific pathogens.
Interferons: Proteins from infected cells signaling nearby cells to prepare an immune response.
Definition: Viruses that can cause cancer.
Mechanism: Insert DNA into host cell and can disrupt cell cycle regulation.
Tumor Types:
Benign: Dormant, non-invasive cells.
Malignant: Active, invasive cancer cells.
Innovative method potentially curing genetic diseases by delivering healthy genes into patient cells using viruses.
Alter virus to eliminate harmful effects.
Insert healthy gene into viral vector.
Virus introduces new gene into patient's cells, promoting production of necessary proteins.
Example: Cystic Fibrosis, leading to blockage in lungs, intestines due to thick mucus.
Steps include:
Virus binding to cell and releasing new gene into nucleus for gene expression
Ensuring altered cells can produce desired proteins and are injected back into the patient's body.