BIO2440 Microbiology Study Guide – Step-by-Step Guidance

Q1. Differentiate a virus from a bacterium.

Background

Topic: Viruses vs. Bacteria

This question tests your understanding of the fundamental differences between viruses and bacteria, including their structure, replication, and classification.

Key Terms:

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

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

Step-by-Step Guidance

1. Consider the basic structural differences: viruses lack cellular structure, while bacteria are prokaryotic cells with membranes and cytoplasm.

2. Think about how each replicates: viruses require a host cell, but bacteria can reproduce independently by binary fission.

3. Reflect on genetic material: viruses may have DNA or RNA, but bacteria always have both DNA and ribosomes for protein synthesis.

4. Consider their response to antibiotics: bacteria can be targeted by antibiotics, but viruses generally cannot.

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Q2. How could the small size of viruses have helped researchers detect viruses before the invention of the electron microscope?

Background

Topic: Virus Discovery and Detection

This question explores how the physical properties of viruses contributed to their early detection, even before advanced imaging technology.

Key Terms:

• Filtration: A method used to separate particles based on size.

• Electron Microscope: A tool that allows visualization of very small particles, such as viruses.

Step-by-Step Guidance

1. Recall that viruses are much smaller than bacteria and can pass through filters that retain bacteria.

2. Think about experiments where infectious agents passed through filters, suggesting the presence of something smaller than bacteria.

3. Consider how researchers inferred the existence of viruses based on disease transmission, even when bacteria were not detected.

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Q3. Describe the chemical and physical structure of both an enveloped and a nonenveloped virus.

Background

Topic: Viral Structure

This question tests your knowledge of the basic components and differences between enveloped and nonenveloped viruses.

Key Terms:

• Capsid: Protein shell surrounding the viral genome.

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

• Spikes: Glycoprotein projections involved in host cell attachment.

Step-by-Step Guidance

1. Identify the core components: all viruses have genetic material (DNA or RNA) and a protein capsid.

2. For enveloped viruses, describe the additional lipid envelope and its origin from the host cell membrane.

3. For nonenveloped viruses, focus on the capsid and any surface proteins or spikes.

4. Consider how these structures affect viral entry and immune evasion.

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Q4. Diagram a nonenveloped polyhedral virus that has spikes.

Background

Topic: Viral Morphology

This question asks you to visualize and represent the structure of a specific type of virus.

Key Terms:

• Polyhedral Virus: A virus with a many-sided (often icosahedral) capsid.

• Spikes: Surface proteins that protrude from the capsid.

Step-by-Step Guidance

1. Start by sketching a geometric shape, such as an icosahedron, to represent the capsid.

2. Add projections (spikes) evenly distributed on the surface of the capsid.

3. Label the capsid, spikes, and indicate the location of the viral genome inside the capsid.

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Q5. Define viral species. How does a virus species differ from a bacterial species?

Background

Topic: Viral Taxonomy

This question tests your understanding of how viruses are classified and how this differs from bacterial classification.

Key Terms:

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

• Bacterial Species: A group of bacteria with similar characteristics that can reproduce by binary fission.

Step-by-Step Guidance

1. Define what constitutes a viral species, focusing on genetic similarity and host range.

2. Contrast this with the definition of a bacterial species, which is based on phenotypic and genetic similarity and reproductive capability.

3. Consider why viruses cannot be classified by reproduction in the same way as bacteria.

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