Viruses, Their Life Cycle, and Microbial History

A set of vocabulary flashcards covering fundamental virology concepts, stages of the viral life cycle, antiviral strategies, and key milestones in microbial evolutionary history.

Virus

A non-living obligate intracellular parasite that uses host cell resources to reproduce.

Capsid

The outer protein coat that encloses a viral genome.

Viral genome types

Possible nucleic-acid forms: dsDNA, ssDNA, dsRNA, or ssRNA.

Viral envelope

Host-derived outer membrane found only in enveloped viruses.

Orthomyxovirus

An enveloped virus that causes influenza.

Adenovirus

A non-enveloped virus that can cause the common cold, bronchitis, and pneumonia.

Attachment (Step 1 of viral reproductive cycle)

Virus binds to specific receptors on the host-cell surface.

Entry (Step 2 of viral reproductive cycle)

Whole virus or its genome enters the host cell.

Genome replication (Step 3 of viral reproductive cycle)

Viral genetic material is copied using host machinery.

Protein synthesis & assembly (Step 4 of viral reproductive cycle)

Host ribosomes produce viral proteins that self-assemble with replicated genomes to form new virions.

Exit (Step 5 of viral reproductive cycle)

New virions leave the host by budding or lysis.

Bacteriophage entry mechanism

Phage injects its genome directly through the bacterial cell wall into the cytoplasm.

Viral budding

Enveloped viruses exit by pushing through the host membrane, acquiring a lipid envelope.

Viral lysis

Non-enveloped viruses rupture the host cell, releasing progeny virions.

Vaccination

Use of dead or weakened pathogens to stimulate an immune response and confer protection.

Antiviral medications

Drugs that inhibit stages of viral development; used against infections like HIV, herpes, and hepatitis B/C.

4.6 billion years ago (Origin of Earth)

Approximate time when Earth formed.

3.5 billion years ago (Oldest prokaryotes)

Earliest fossil evidence of prokaryotic life.

2.3 billion years ago (Great Oxygenation Event)

Atmospheric O₂ first appeared due to photosynthetic microbes.

2.0–1.5 billion years ago (Oldest eukaryotes)

Fossil evidence for the first eukaryotic organisms.