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Study Guide: Viruses and Prions (Microbiology Exam Prep)

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Q1. Differentiate between bacteria and virus particles regarding size, nucleic acid, shape, replication, and sensitivity to antibiotics.

Background

Topic: Microbial Cell Types and Viral Structure

This question tests your understanding of the fundamental differences between bacteria (prokaryotic cells) and viruses (acellular infectious agents), focusing on their physical and genetic characteristics, replication strategies, and response to antibiotics.

Key Terms:

  • Size: Relative dimensions of bacteria vs. viruses (measured in micrometers vs. nanometers).

  • Nucleic Acid: Type of genetic material (DNA or RNA, single or double-stranded).

  • Shape: Morphology (e.g., cocci, bacilli for bacteria; icosahedral, helical for viruses).

  • Replication: How each reproduces (binary fission vs. host-dependent replication).

  • Sensitivity to Antibiotics: Whether antibiotics are effective and why.

Step-by-Step Guidance

  1. List the typical size ranges for bacteria and viruses. (Hint: Bacteria are generally larger than viruses.)

  2. Identify the types of nucleic acids found in bacteria and in viruses. (Consider whether they have DNA, RNA, or both.)

  3. Describe the general shapes of bacteria and viruses, noting any structural differences.

  4. Explain how bacteria replicate compared to how viruses replicate. (Think about whether they need a host cell.)

  5. Discuss why antibiotics affect bacteria but not viruses, referencing their cellular structure and metabolic pathways.

Try solving on your own before revealing the answer!

Q2. Describe the parts of a viral particle and their purpose: Genome, Capsid, Envelope, Spikes.

Background

Topic: Viral Structure

This question focuses on the basic components of a virus and the function of each part in the viral life cycle.

Key Terms:

  • Genome: The genetic material (DNA or RNA) of the virus.

  • Capsid: Protein shell that encases the genome.

  • Envelope: Lipid membrane derived from the host cell.

  • Spikes: Glycoproteins protruding from the envelope or capsid.

Step-by-Step Guidance

  1. Define what the viral genome is and its role in infection.

  2. Describe the structure and function of the capsid.

  3. Explain what the envelope is, how viruses acquire it, and its significance.

  4. Discuss the function of spikes and how they contribute to host cell recognition and entry.

Try solving on your own before revealing the answer!

Q3. Explain the following terms: host range, tissue tropism, burst time, enveloped virus, naked virus.

Background

Topic: Viral Host Interactions and Viral Structure

This question assesses your understanding of how viruses interact with hosts and the terminology used to describe viral properties.

Key Terms:

  • Host Range: The spectrum of host species a virus can infect.

  • Tissue Tropism: Specific tissues or cell types a virus can infect within a host.

  • Burst Time: Time from viral entry to host cell lysis and release of new virions.

  • Enveloped Virus: Virus with a lipid membrane surrounding the capsid.

  • Naked Virus: Virus lacking an envelope; only genome and capsid present.

Step-by-Step Guidance

  1. Define each term in your own words, using examples where possible.

  2. Explain why host range and tissue tropism are important for viral infection and disease.

  3. Describe how burst time relates to the viral replication cycle.

  4. Contrast enveloped and naked viruses in terms of structure and susceptibility to environmental factors.

Try solving on your own before revealing the answer!

Q4a. Differentiate between virulent vs. temperate bacteriophages and lytic vs. lysogenic cycles.

Background

Topic: Bacteriophage Life Cycles

This question tests your knowledge of the types of bacteriophages and the two main cycles of viral replication in bacteria.

Key Terms:

  • Virulent Phage: Only undergoes the lytic cycle.

  • Temperate Phage: Can undergo both lytic and lysogenic cycles.

  • Lytic Cycle: Results in host cell lysis and release of new phages.

  • Lysogenic Cycle: Viral genome integrates into host DNA and replicates with it.

Step-by-Step Guidance

  1. Define what makes a phage virulent or temperate.

  2. Describe the main events in the lytic cycle.

  3. Outline the steps of the lysogenic cycle and how it differs from the lytic cycle.

  4. Explain the biological significance of each cycle for the virus and the host.

Try solving on your own before revealing the answer!

Q4b. Define “lysogenic bacteria” and “prophage.”

Background

Topic: Lysogeny and Viral Integration

This question focuses on terminology related to the lysogenic cycle of bacteriophages.

Key Terms:

  • Lysogenic Bacteria: Bacteria that harbor a dormant phage genome.

  • Prophage: The integrated phage DNA within the bacterial chromosome.

Step-by-Step Guidance

  1. Define what is meant by lysogenic bacteria.

  2. Explain how a prophage forms and its role in the lysogenic cycle.

Try solving on your own before revealing the answer!

Q5. Describe the six steps of animal virus replication.

Background

Topic: Animal Virus Life Cycle

This question tests your ability to recall and explain the sequential steps involved in the replication of animal viruses.

Key Terms:

  • Attachment

  • Penetration

  • Uncoating

  • Biosynthesis

  • Maturation (Assembly)

  • Release

Step-by-Step Guidance

  1. List each of the six steps in order.

  2. Briefly describe what happens during each step, focusing on the main events.

  3. Note any differences that might occur depending on whether the virus is enveloped or naked.

Try solving on your own before revealing the answer!

Q6. Contrast Prophage vs. Provirus, similarities and differences.

Background

Topic: Viral Integration in Prokaryotes vs. Eukaryotes

This question asks you to compare the integrated forms of viral genomes in bacteria (prophage) and in animal cells (provirus).

Key Terms:

  • Prophage: Phage DNA integrated into bacterial chromosome.

  • Provirus: Viral DNA integrated into eukaryotic (animal) host genome.

Step-by-Step Guidance

  1. Define both terms and specify the type of host cell involved.

  2. List similarities in how they are maintained within the host genome.

  3. Identify key differences, such as reactivation and effects on the host.

Try solving on your own before revealing the answer!

Q7. List and explain the six types of methods used to identify viruses.

Background

Topic: Viral Identification Techniques

This question tests your knowledge of laboratory and molecular methods used to detect and identify viruses.

Key Terms:

  • Methods may include: Cytopathic effects, Serological tests, Nucleic acid tests, Electron microscopy, Cell culture, Hemagglutination, etc.

Step-by-Step Guidance

  1. List six different methods used for viral identification.

  2. For each method, briefly describe how it works and what it detects.

  3. Note any advantages or limitations of each method.

Try solving on your own before revealing the answer!

Q8. How does interferon prevent viral infections?

Background

Topic: Antiviral Immunity

This question focuses on the mechanism by which interferons inhibit viral replication and spread.

Key Terms:

  • Interferon: Host-produced proteins with antiviral activity.

  • Antiviral State: Cellular changes that inhibit viral replication.

Step-by-Step Guidance

  1. Define what interferons are and when they are produced.

  2. Describe the signaling pathway that leads to the antiviral state in neighboring cells.

  3. Explain how this state prevents viral replication (e.g., inhibition of protein synthesis, degradation of viral RNA).

Try solving on your own before revealing the answer!

Q9. Describe the mechanism of action of different antiviral drugs.

Background

Topic: Antiviral Chemotherapy

This question tests your understanding of how various antiviral drugs interfere with the viral life cycle.

Key Terms:

  • Mechanisms may include: Inhibition of viral entry, nucleic acid synthesis, protease activity, or release.

Step-by-Step Guidance

  1. List several classes of antiviral drugs and their targets (e.g., reverse transcriptase inhibitors, protease inhibitors).

  2. For each class, briefly explain how the drug disrupts the viral replication process.

  3. Provide examples of viruses targeted by each drug class.

Try solving on your own before revealing the answer!

Q10. Differentiate between inactivated, attenuated, subunit vaccines, and RNA vaccines.

Background

Topic: Viral Vaccines

This question assesses your knowledge of the main types of vaccines used to prevent viral infections and their mechanisms.

Key Terms:

  • Inactivated Vaccine: Contains killed virus particles.

  • Attenuated Vaccine: Contains live, weakened virus.

  • Subunit Vaccine: Contains purified viral components (e.g., proteins).

  • RNA Vaccine: Contains mRNA encoding viral proteins.

Step-by-Step Guidance

  1. Define each vaccine type and describe how it is produced.

  2. Explain how each vaccine stimulates the immune system.

  3. Compare the advantages and disadvantages of each type (e.g., safety, immune response, storage).

Try solving on your own before revealing the answer!

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