Skip to main content
뒤로

Microbiology: Viruses, Viral Structure, and Viral Life Cycles – Guided Study

주석실무비디오 수업

스터디 가이드 - 스마트 노트

자료에 맞춘 맞춤형 노트, 핵심 정의, 예시, 맥락을 확장해 제공합니다.

Q13-1. Differentiate a virus from a bacterium.

Background

Topic: Viruses vs. Bacteria

This question tests your understanding of the fundamental differences between viruses and bacteria, which are two major types of microorganisms studied in microbiology.

Key Terms:

  • Virus: A non-cellular infectious agent that requires a host cell to replicate.

  • Bacterium: A unicellular, prokaryotic organism capable of independent life and reproduction.

Step-by-Step Guidance

  1. Consider the structural differences: Think about whether viruses and bacteria have cellular structures like cell walls, membranes, and organelles.

  2. Think about their genetic material: Do both have DNA, or do they differ in the type of nucleic acid present?

  3. Reflect on their replication: Can both reproduce independently, or does one require a host cell?

  4. Consider their size and visibility under a microscope.

Try solving on your own before revealing the answer!

Final Answer:

Viruses are acellular, much smaller than bacteria, and cannot reproduce on their own—they require a host cell for replication. Bacteria are unicellular prokaryotes that can reproduce independently by binary fission and have cellular structures such as cell walls and membranes.

Q13-2. Describe the chemical and physical structure of both an enveloped and a nonenveloped virus.

Background

Topic: Viral Structure

This question focuses on the differences in structure between enveloped and nonenveloped (naked) viruses, which is important for understanding viral classification and infection mechanisms.

Key Terms:

  • Capsid: Protein coat surrounding the viral genome.

  • Envelope: Lipid membrane derived from the host cell, present in some viruses.

  • Nucleic Acid: Genetic material (DNA or RNA) inside the virus.

Step-by-Step Guidance

  1. Identify the basic components all viruses share (nucleic acid and capsid).

  2. Describe what makes an enveloped virus different—what additional structure does it have?

  3. Explain the chemical composition of the envelope and its origin.

  4. Contrast this with nonenveloped viruses, focusing on what they lack compared to enveloped viruses.

Try solving on your own before revealing the answer!

Final Answer:

Enveloped viruses have a nucleic acid core (DNA or RNA), a protein capsid, and an outer lipid envelope derived from the host cell membrane, often with embedded viral proteins (spikes). Nonenveloped viruses lack this lipid envelope and consist only of the nucleic acid and capsid.

Q13-3. Define viral species.

Background

Topic: Viral Taxonomy

This question is about the classification of viruses and what constitutes a 'species' in virology, which differs from the definition in cellular organisms.

Key Terms:

  • Viral species: A group of viruses sharing the same genetic information and ecological niche.

  • Taxonomy: The science of classification.

Step-by-Step Guidance

  1. Recall how species are defined for cellular organisms and consider how this might differ for viruses.

  2. Think about the criteria used for grouping viruses (genetic similarity, host range, etc.).

  3. Consider the concept of an ecological niche in the context of viruses.

Try solving on your own before revealing the answer!

Final Answer:

A viral species is a group of viruses sharing the same genetic information and ecological niche (host range), and are considered to be members of the same species if they are similar in genome and infect the same host type.

Q13-4. Give an example of a family, genus, and common name for a virus.

Background

Topic: Viral Classification

This question tests your knowledge of the hierarchical system used to classify viruses, including family, genus, and common names.

Key Terms:

  • Family: A higher taxonomic category (often ends in -viridae).

  • Genus: A group within a family (often ends in -virus).

  • Common name: The name by which the virus is generally known.

Step-by-Step Guidance

  1. Recall examples of well-known viruses and their classification.

  2. Identify the family name (look for the -viridae ending).

  3. Identify the genus name (look for the -virus ending).

  4. State the common name used in everyday language or media.

Try solving on your own before revealing the answer!

Final Answer:

Example: Family: Herpesviridae; Genus: Simplexvirus; Common name: Herpes simplex virus (HSV).

Q13-5. Describe how bacteriophages are cultured.

Background

Topic: Culturing Viruses

This question is about laboratory techniques for growing bacteriophages (viruses that infect bacteria), which is essential for studying their biology.

Key Terms:

  • Bacteriophage: A virus that infects bacteria.

  • Plaque assay: A method to quantify viruses based on clear zones (plaques) formed on a bacterial lawn.

Step-by-Step Guidance

  1. Recall the need for a host (bacterial cells) to culture bacteriophages.

  2. Think about the use of agar plates and the formation of plaques.

  3. Consider the steps involved: mixing phages with bacteria, pouring onto agar, and incubation.

  4. Reflect on how plaques indicate the presence of bacteriophages.

Try solving on your own before revealing the answer!

Final Answer:

Bacteriophages are cultured by mixing them with susceptible bacteria and soft agar, then pouring this mixture onto a nutrient agar plate. After incubation, clear zones called plaques appear where phages have lysed the bacteria.

Q13-6. Describe how animal viruses are cultured.

Background

Topic: Culturing Animal Viruses

This question focuses on laboratory methods for growing animal viruses, which differ from bacteriophage culture techniques.

Key Terms:

  • Cell culture: Growing animal cells in vitro for virus propagation.

  • Embryonated eggs: Fertilized eggs used as a medium for viral growth.

Step-by-Step Guidance

  1. Recall the need for living host cells for animal virus replication.

  2. Think about the use of cell cultures (monolayers) and how viruses cause cytopathic effects.

  3. Consider alternative methods, such as inoculation into embryonated eggs or live animals.

  4. Reflect on how viral growth is detected in these systems.

Try solving on your own before revealing the answer!

Final Answer:

Animal viruses are cultured using living cells, such as cell cultures (monolayers), embryonated eggs, or live animals. Viral growth is detected by cytopathic effects, embryo death, or visible lesions.

Q13-7. List three techniques used to identify viruses.

Background

Topic: Viral Identification

This question is about laboratory methods for identifying viruses, which is crucial for diagnosis and research.

Key Terms:

  • Serological tests: Detect viral antigens or antibodies.

  • Molecular methods: Detect viral nucleic acids (e.g., PCR).

  • Electron microscopy: Visualize viral particles.

Step-by-Step Guidance

  1. Think about methods that detect viral proteins or genetic material.

  2. Consider techniques that use antibodies to identify viruses.

  3. Recall imaging techniques that can directly visualize viruses.

Try solving on your own before revealing the answer!

Final Answer:

Three techniques used to identify viruses are: serological tests (e.g., ELISA), molecular methods (e.g., PCR), and electron microscopy.

Q13-8. Describe the lytic cycle of T-even bacteriophages.

Background

Topic: Viral Life Cycles

This question focuses on the steps of the lytic cycle, a process by which bacteriophages infect and destroy bacterial cells.

Key Terms:

  • Lytic cycle: The process by which a virus replicates and lyses the host cell.

  • T-even bacteriophages: A group of well-studied lytic phages (e.g., T4).

Step-by-Step Guidance

  1. List the main stages of the lytic cycle (attachment, penetration, biosynthesis, maturation, release).

  2. Describe what happens during attachment and penetration.

  3. Explain the biosynthesis phase (replication of viral components).

  4. Outline the maturation and release steps, but stop before detailing the final outcome.

Try solving on your own before revealing the answer!

Final Answer:

The lytic cycle of T-even bacteriophages involves: 1) Attachment to the bacterial cell, 2) Penetration of viral DNA, 3) Biosynthesis of viral components, 4) Maturation (assembly of new phages), and 5) Release (lysis of the host cell).

Q13-9. Describe the lysogenic cycle of bacteriophage Lambda virus.

Background

Topic: Viral Life Cycles

This question is about the lysogenic cycle, where the viral genome integrates into the host genome and can remain dormant.

Key Terms:

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

  • Prophage: The integrated viral DNA.

Step-by-Step Guidance

  1. Recall the initial steps (attachment and penetration) similar to the lytic cycle.

  2. Describe how the viral DNA integrates into the host chromosome (forming a prophage).

  3. Explain how the prophage is replicated along with the host DNA during cell division.

  4. Consider what triggers the prophage to exit the host genome and enter the lytic cycle, but stop before detailing this transition.

Try solving on your own before revealing the answer!

Final Answer:

In the lysogenic cycle, the Lambda phage DNA integrates into the host's chromosome as a prophage, replicates with the host cell, and can remain dormant until certain conditions trigger entry into the lytic cycle.

Q13-10. Compare and contrast the multiplication cycle of DNA- and RNA-containing animal viruses.

Background

Topic: Viral Replication

This question asks you to analyze similarities and differences in how DNA and RNA animal viruses replicate inside host cells.

Key Terms:

  • DNA virus: Virus with DNA as genetic material.

  • RNA virus: Virus with RNA as genetic material.

  • Replication site: Where in the cell replication occurs (nucleus or cytoplasm).

Step-by-Step Guidance

  1. List the general steps of viral multiplication (attachment, entry, uncoating, replication, assembly, release).

  2. Identify where DNA viruses typically replicate (nucleus) and where RNA viruses usually replicate (cytoplasm).

  3. Consider the enzymes required for replication (host or viral polymerases).

  4. Note any unique steps for RNA viruses, such as reverse transcription in retroviruses.

Try solving on your own before revealing the answer!

Final Answer:

DNA viruses usually replicate in the host cell nucleus using host enzymes, while RNA viruses typically replicate in the cytoplasm and often require their own RNA-dependent RNA polymerase. Retroviruses (RNA viruses) use reverse transcriptase to make DNA from RNA.

Q13-11. Define oncogene and transformed cell.

Background

Topic: Viruses and Cancer

This question is about the role of viruses in cancer development and the definitions of key terms related to oncogenesis.

Key Terms:

  • Oncogene: A gene that can cause a normal cell to become cancerous.

  • Transformed cell: A cell that has acquired properties of uncontrolled growth.

Step-by-Step Guidance

  1. Recall what happens when a normal gene is mutated or activated inappropriately.

  2. Think about how viral infection can lead to transformation of a cell.

  3. Define what is meant by a 'transformed' cell in the context of cancer biology.

Try solving on your own before revealing the answer!

Final Answer:

An oncogene is a gene that has the potential to cause cancer, often by promoting uncontrolled cell division. A transformed cell is one that has undergone changes to become cancerous, typically showing loss of normal growth regulation.

Q13-12. Discuss the relationship between DNA- and RNA-containing viruses and cancer.

Background

Topic: Viral Oncogenesis

This question explores how both DNA and RNA viruses can contribute to the development of cancer in their hosts.

Key Terms:

  • Oncogenic virus: A virus capable of causing cancer.

  • Integration: Viral DNA or cDNA integrating into host genome.

Step-by-Step Guidance

  1. Recall examples of DNA and RNA viruses known to cause cancer (e.g., HPV, HTLV).

  2. Consider how viral genetic material can disrupt host cell regulation.

  3. Think about the mechanisms: integration of viral DNA, activation of oncogenes, or inhibition of tumor suppressor genes.

  4. Reflect on the differences in how DNA and RNA viruses achieve these effects.

Try solving on your own before revealing the answer!

Final Answer:

Both DNA and RNA viruses can cause cancer by integrating their genetic material into the host genome, disrupting normal cell regulation. DNA viruses (e.g., HPV) often integrate directly, while RNA viruses (e.g., retroviruses) use reverse transcription to insert cDNA into the host genome.

Q13-13. Provide an example of a latent viral infection.

Background

Topic: Latent Infections

This question is about viruses that can remain dormant in the host and reactivate later.

Key Terms:

  • Latent infection: A viral infection that remains inactive within the host for a period.

  • Reactivation: The process by which a latent virus becomes active again.

Step-by-Step Guidance

  1. Recall viruses known for latency (e.g., herpesviruses).

  2. Think about diseases that can recur after a period of dormancy.

  3. Identify a specific virus and the condition it causes.

Try solving on your own before revealing the answer!

Final Answer:

An example of a latent viral infection is herpes simplex virus (HSV), which can remain dormant in nerve cells and reactivate to cause cold sores.

Q13-14. Differentiate between latent and persistent viral infections.

Background

Topic: Types of Viral Infections

This question asks you to distinguish between two types of long-term viral infections.

Key Terms:

  • Latent infection: Virus remains inactive for a period, with possible reactivation.

  • Persistent infection: Virus is continuously present and often detectable.

Step-by-Step Guidance

  1. Define what happens during a latent infection (periods of inactivity and reactivation).

  2. Define what happens during a persistent infection (continuous viral presence).

  3. Compare the detectability of the virus during each type of infection.

  4. Think of examples for each type.

Try solving on your own before revealing the answer!

Final Answer:

Latent infections involve periods where the virus is inactive and undetectable, with possible reactivation (e.g., HSV). Persistent infections involve continuous, often low-level viral replication and presence (e.g., HIV, hepatitis B).

Q13-15. Differentiate virus, viroid, and prion.

Background

Topic: Infectious Agents

This question is about the differences among three types of infectious agents: viruses, viroids, and prions.

Key Terms:

  • Virus: Infectious agent with nucleic acid and protein coat.

  • Viroid: Infectious RNA molecule without a protein coat.

  • Prion: Infectious protein without nucleic acid.

Step-by-Step Guidance

  1. Define the structural components of a virus.

  2. Describe what makes a viroid unique (RNA only, no protein coat).

  3. Explain what a prion is (protein only, no nucleic acid).

  4. Consider the types of diseases each causes and their hosts.

Try solving on your own before revealing the answer!

Final Answer:

Viruses consist of nucleic acid (DNA or RNA) and a protein coat; viroids are small, circular RNA molecules without a protein coat (infect plants); prions are infectious proteins without nucleic acid (cause diseases like mad cow in animals).

Q13-16. Describe the lytic cycle for a plant virus.

Background

Topic: Plant Virus Life Cycle

This question is about how plant viruses infect and destroy host cells through the lytic cycle.

Key Terms:

  • Lytic cycle: Viral replication resulting in host cell lysis.

  • Plant virus: Virus that infects plant cells.

Step-by-Step Guidance

  1. Recall the general steps of the lytic cycle (attachment, entry, replication, assembly, release).

  2. Consider how plant viruses enter host cells (often via wounds or vectors).

  3. Describe replication and assembly of new viral particles inside the plant cell.

  4. Explain how new viruses are released, but stop before detailing the final outcome.

Try solving on your own before revealing the answer!

Final Answer:

The lytic cycle for a plant virus involves entry into the plant cell (often through wounds), replication of viral components, assembly of new viruses, and release of viruses as the host cell is damaged or lysed.

Q13-17. Discuss how a protein can be infectious.

Background

Topic: Prions

This question is about prions, which are infectious proteins that cause disease without nucleic acids.

Key Terms:

  • Prion: Infectious protein that can induce abnormal folding of normal proteins.

  • Protein misfolding: The process by which a protein adopts an abnormal structure.

Step-by-Step Guidance

  1. Recall what a prion is and how it differs from other infectious agents.

  2. Think about how a misfolded protein can interact with normal proteins.

  3. Consider the consequences of protein misfolding in the host organism.

  4. Reflect on diseases caused by prions.

Try solving on your own before revealing the answer!

Final Answer:

A protein can be infectious if it is a prion, which causes disease by inducing normal proteins to misfold into the abnormal prion form, leading to neurodegenerative diseases like Creutzfeldt-Jakob disease.

Pearson Logo

스터디 프렙