Comprehensive Guidance for Microbiology Final Exam Study Guide (BIOM 250)

Study Guide - Smart Notes

Tailored notes based on your materials, expanded with key definitions, examples, and context.

Q1. What is a virus?

Background

Topic: Introduction to Virology

This question tests your understanding of the basic definition and nature of viruses, which are central to microbiology and infectious disease.

Key Terms

Virus: A microscopic infectious agent that can only replicate inside the living cells of an organism.
Obligate intracellular parasite: An organism or agent that must live within a host cell to reproduce.

Step-by-Step Guidance

Consider what distinguishes viruses from other microorganisms (such as bacteria or fungi).
Think about the structural components of viruses (e.g., genetic material, protein coat).
Recall that viruses require a host cell for replication and cannot carry out metabolism on their own.

Try describing what a virus is in your own words before checking the answer!

Final Answer:

A virus is a non-living, obligate intracellular parasite composed of genetic material (DNA or RNA) surrounded by a protein coat (capsid), and sometimes a lipid envelope. It can only reproduce by infecting a host cell.

Q2. What are the properties of viruses?

Background

Topic: Viral Structure and Characteristics

This question asks you to recall the defining features that set viruses apart from other microbes.

Key Terms

Capsid: Protein shell that encloses the viral genome.
Envelope: Lipid membrane derived from the host cell, present in some viruses.
Genome: The genetic material, which can be DNA or RNA, single- or double-stranded.

Step-by-Step Guidance

List the basic structural components common to all viruses.
Consider how viruses differ from living cells (e.g., lack of metabolism, inability to reproduce independently).
Think about the diversity in viral genomes (DNA vs. RNA, single- vs. double-stranded).
Recall that some viruses have an envelope, while others are naked (non-enveloped).

Try listing the main properties of viruses before revealing the answer!

Final Answer:

Viruses are acellular, have either DNA or RNA as genetic material, are surrounded by a protein capsid (and sometimes an envelope), lack independent metabolism, and require a host cell for replication.

Q3. What are two different classes of viruses based on nucleic acid?

Background

Topic: Viral Classification

This question focuses on how viruses are categorized according to the type of genetic material they contain.

Key Terms

DNA virus: Virus with DNA as its genetic material.
RNA virus: Virus with RNA as its genetic material.

Step-by-Step Guidance

Recall that viruses can be classified by the type of nucleic acid they possess.
Think about the implications of having DNA or RNA for replication and mutation rates.

Try naming the two main classes before checking the answer!

Final Answer:

The two main classes are DNA viruses and RNA viruses.

Q4. What is the difference between a naked and an enveloped virus?

Background

Topic: Viral Structure

This question tests your understanding of the structural differences between viruses and how these differences affect their properties.

Key Terms

Naked virus: Virus lacking a lipid envelope; only has a protein capsid.
Enveloped virus: Virus with a lipid membrane (envelope) surrounding the capsid, usually derived from the host cell membrane.

Step-by-Step Guidance

Identify the structural components of both types of viruses.
Consider how the presence or absence of an envelope affects viral stability and transmission.
Think about examples of each type (e.g., poliovirus is naked, influenza virus is enveloped).

Try explaining the difference before revealing the answer!

Final Answer:

Naked viruses lack a lipid envelope and consist only of a nucleic acid genome surrounded by a protein capsid, while enveloped viruses have an additional lipid membrane derived from the host cell.

Q5. How do viruses multiply? (Attachment, Penetration, Biosynthesis, Maturation, Release)

Background

Topic: Viral Replication Cycle

This question asks you to outline the general steps by which viruses infect host cells and produce new viral particles.

Key Terms

Attachment: Virus binds to specific receptors on the host cell surface.
Penetration: Entry of viral genome into the host cell.
Biosynthesis: Host cell machinery is used to replicate viral genome and synthesize viral proteins.
Maturation: Assembly of viral components into complete virions.
Release: New virions exit the host cell, often destroying it.

Step-by-Step Guidance

List the five main stages of the viral replication cycle.
Briefly describe what happens at each stage.
Consider how these steps may differ between DNA and RNA viruses, or between enveloped and naked viruses.

Try outlining the steps before checking the answer!

Final Answer:

Viruses multiply by attaching to a host cell, penetrating the cell membrane, using the host's machinery to synthesize viral components, assembling new virions, and releasing them to infect new cells.

Q6. What occurs during a latent infection? Give examples.

Background

Topic: Viral Pathogenesis

This question tests your understanding of how some viruses can remain dormant in the host and reactivate later.

Key Terms

Latent infection: Viral genome persists in host cells without producing new virions for extended periods.
Reactivation: The process by which a latent virus resumes active replication.

Step-by-Step Guidance

Define what is meant by a latent infection.
Think of viruses known for latency (e.g., herpesviruses).
Consider what triggers reactivation and what symptoms may result.

Try describing what happens during latency and list examples before revealing the answer!

Final Answer:

During a latent infection, the virus remains dormant within host cells and does not produce new virions. Examples include herpes simplex virus (cold sores) and varicella-zoster virus (chickenpox/shingles).

Q7. What occurs during a persistent infection? Give examples. Is this a chronic or acute infection?

Background

Topic: Viral Pathogenesis

This question asks you to distinguish persistent infections from latent and acute infections, and to provide examples.

Key Terms

Persistent infection: Virus is continuously present in the host, often at low levels, for long periods.
Chronic infection: Long-lasting infection with ongoing viral replication.
Acute infection: Rapid onset, short duration infection.

Step-by-Step Guidance

Define persistent infection and how it differs from latent and acute infections.
Think of examples of viruses that cause persistent infections (e.g., hepatitis B or C).
Determine whether persistent infections are considered chronic or acute.

Try explaining persistent infections and give examples before checking the answer!

Final Answer:

Persistent infections involve continuous viral presence and replication over a long period, often leading to chronic disease. Examples include hepatitis B and C viruses.

Q8. Can viruses cause cancer? If so, how? Give an example.

Background

Topic: Oncogenic Viruses

This question tests your knowledge of the relationship between viral infections and cancer development.

Key Terms

Oncogenic virus: Virus capable of causing cancer.
Transformation: Process by which a normal cell becomes cancerous.

Step-by-Step Guidance

Recall that some viruses can integrate their genetic material into host DNA.
Consider how viral genes may disrupt normal cell cycle regulation.
Think of examples of viruses linked to cancer (e.g., human papillomavirus, hepatitis B).

Try explaining how viruses can cause cancer and give an example before revealing the answer!

Final Answer:

Yes, some viruses can cause cancer by integrating their DNA into host cells and disrupting normal cell cycle control. An example is human papillomavirus (HPV), which can cause cervical cancer.