What are the key structural components of a virus?
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Mastering this deck will enhance your ability to identify viral structures, understand their replication strategies, and classify viruses accurately—skills essential for diagnosis, research, and developing antiviral strategies in clinical practice.
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| 1 | What are the key structural components of a virus? |
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Understanding viral architecture, life cycle, and taxonomy of medically important viruses.
Viruses generally consist of a nucleic acid genome (DNA or RNA), a protein capsid that encases the genome, and sometimes an outer lipid envelope derived from host cell membranes. |
| Think of a virus as a 'nucleic acid core' wrapped in a 'protein shell.' |
| 2 | What is the primary function of the viral capsid? | The capsid protects the viral nucleic acid from environmental damage and facilitates the attachment and entry into host cells. | Capsid = protective shell and key to cell entry. |
| 3 | Which viruses possess an outer lipid envelope, and how is it acquired? | Enveloped viruses acquire their lipid envelope from the host cell membrane during budding or release, examples include influenza and HIV. | Envelope = host-derived lipid layer. |
| 4 | Describe the difference between positive-sense and negative-sense RNA viruses. | Positive-sense RNA viruses have genomes that can directly serve as mRNA for protein synthesis, whereas negative-sense RNA genomes are complementary to mRNA and require transcription into positive-sense RNA before translation. | Think of positive-sense as ready-to-use mRNA; negative-sense as needing transcription first. |
| 5 | What is the Baltimore classification system? | The Baltimore system classifies viruses based on their type of nucleic acid and replication strategy, dividing them into seven groups from I to VII. | Baltimore = 'Biology of nucleic acids and replication.' |
| 6 | Name the seven Baltimore virus groups. | 1. Double-stranded DNA viruses, 2. Single-stranded DNA viruses, 3. Double-stranded RNA viruses, 4. Positive-sense single-stranded RNA viruses, 5. Negative-sense single-stranded RNA viruses, 6. Reverse-transcribing DNA viruses, 7. Reverse-transcribing RNA viruses. | Think of the groups as based on DNA/RNA type and sense. |
| 7 | What is the typical replication cycle of an obligate intracellular virus? | It involves attachment to the host cell, entry, uncoating of the viral genome, replication of nucleic acids, assembly of new virions, and release from the host cell. | Viral life cycle = attack, replicate, assemble, exit. |
| 8 | How do DNA viruses generally replicate within host cells? | DNA viruses typically replicate in the nucleus using host or viral DNA polymerases, often utilizing the host's replication machinery. | DNA = nuclear replication in most cases. |
| 9 | How do (+)ssRNA viruses differ from (-)ssRNA viruses in replication? | (+ )ssRNA viruses can directly serve as mRNA to produce proteins, while (-) ssRNA viruses must first be transcribed into (+) sense RNA by an RNA-dependent RNA polymerase. | Sense determines if the genome is ready for translation. |
| 10 | What is the significance of viral envelope glycoproteins? | Glycoproteins facilitate attachment to host cell receptors, mediating entry and determining host and tissue specificity. | Glycoproteins = keys to host cell entry. |
| 11 | Name two common receptors used by viruses for cell entry. | Examples include CD4 for HIV and sialic acid residues for influenza virus. | Receptors are like 'locks' that viruses 'key' into. |
| 12 | What are the main methods by which viruses exit host cells? | Viruses exit via cell lysis, budding (for enveloped viruses), or exocytosis. | Exit strategies include 'pop' (lysis) or 'slide out' (budding). |
| 13 | What is the purpose of viral latency, and which viruses are known for it? | Latency allows viruses to persist in host cells without active replication, enabling reactivation later; examples include herpesviruses and HIV. | Latency = viral 'sleep mode'. |
| 14 | Which viruses are classified as oncogenic, and how do they contribute to cancer? | Viruses like HPV, EBV, and Hepatitis B and C can integrate into host genomes or alter cell regulation, promoting oncogenesis. | Oncogenic viruses can turn normal cells into cancer cells. |
| 15 | What features are used to classify viruses taxonomically? | Features include genome type, replication strategy, morphology, host range, and mode of transmission. | Taxonomy = 'family resemblance' based on structure and genetics. |
| 16 | Name the family of viruses that includes herpesviruses. | Herpesviridae. | Herpesviruses are large, enveloped DNA viruses. |
| 17 | Which virus family includes the causative agent of influenza? | Orthomyxoviridae. | Orthomyxoviruses are negative-sense RNA viruses with segmented genomes. |
| 18 | What structural feature distinguishes piconaviruses (e.g., poliovirus) from other virus families? | They are small, non-enveloped, icosahedral viruses with a single-stranded positive-sense RNA genome. | Small, simple, and non-enveloped. |
| 19 | Explain the concept of viral tropism. | Viral tropism refers to the preference of a virus for specific cell types or tissues, determined by receptor availability and cellular factors. | Tropism = 'viral target preference.' |
| 20 | How do antiviral drugs typically interfere with viral replication? | They target specific stages such as entry, uncoating, nucleic acid synthesis, or assembly, e.g., reverse transcriptase inhibitors or protease inhibitors. | Target the viral 'assembly line.' |
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