Microbiology Exam 3 Study Guide – Step-by-Step Guidance

Study Guide - Smart Notes

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Q1. How is rRNA used to classify organisms?

Background

Topic: Molecular Phylogeny and Classification

This question tests your understanding of how ribosomal RNA (rRNA) sequences are used in the classification and evolutionary study of organisms, especially in microbiology.

Key Terms and Concepts:

rRNA (ribosomal RNA): A type of RNA that is a component of the ribosome and is highly conserved among organisms.
Phylogenetic tree: A diagram showing evolutionary relationships.
Sequence comparison: Analyzing similarities and differences in genetic sequences.

Step-by-Step Guidance

Recall that rRNA genes (such as 16S rRNA in prokaryotes) are present in all living organisms and evolve slowly, making them useful for comparing distant relationships.
Understand that scientists sequence the rRNA genes from different organisms and compare these sequences to identify similarities and differences.
Recognize that greater sequence similarity suggests a closer evolutionary relationship, while more differences indicate more distant relationships.
Consider how these comparisons are used to construct phylogenetic trees, which help classify organisms into domains and other taxonomic groups.

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Q2. Are viruses composed of cells?

Background

Topic: Structure of Viruses

This question tests your understanding of the basic structure of viruses and how they differ from cellular life forms.

Key Terms:

Virus: An infectious agent composed of genetic material (DNA or RNA) and a protein coat, sometimes with a lipid envelope.
Cell: The basic structural and functional unit of living organisms.

Step-by-Step Guidance

Recall the definition of a cell and the components that make up a typical cell (membrane, cytoplasm, organelles, etc.).
Think about the structure of a virus and what components it contains.
Compare the structure of viruses to that of cells to determine if viruses meet the criteria for being composed of cells.

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Q3. Are biochemical tests used to test for the presence of enzymes?

Background

Topic: Microbial Identification

This question is about the use of biochemical tests in identifying microorganisms based on their metabolic properties.

Key Terms:

Biochemical test: Laboratory tests that detect metabolic activities of microbes, often by detecting enzymes or metabolic products.
Enzyme: A protein that catalyzes biochemical reactions.

Step-by-Step Guidance

Recall what biochemical tests are and what they measure in microorganisms.
Think about examples of biochemical tests (e.g., catalase test, oxidase test) and what they detect.
Consider whether these tests are designed to detect the presence of specific enzymes or other metabolic products.

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Q4. Is blood a portal of entry for microorganisms?

Background

Topic: Pathogenesis and Portals of Entry

This question tests your knowledge of how pathogens enter the human body and what is considered a portal of entry.

Key Terms:

Portal of entry: The site through which microorganisms enter the host.
Bloodstream: The circulating blood within the body.

Step-by-Step Guidance

List the common portals of entry for pathogens (e.g., mucous membranes, skin, respiratory tract).
Consider whether blood is typically an initial entry point or if pathogens usually enter through other sites before reaching the bloodstream.
Think about examples of how pathogens might reach the blood and whether this is considered a portal of entry.

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Q5. Can bacteria have an RNA genome?

Background

Topic: Microbial Genetics

This question tests your understanding of the genetic material found in bacteria compared to other microorganisms like viruses.

Key Terms:

Genome: The complete set of genetic material in an organism.
DNA vs. RNA genome: Some organisms have DNA as their genetic material, while some viruses have RNA genomes.

Step-by-Step Guidance

Recall the typical genetic material found in bacteria.
Compare this to the genetic material found in viruses.
Consider whether any known bacteria have RNA as their sole genetic material.

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Q6. Which bacteria is gram +, facultative anaerobes, grow slowly as branching filaments, have a club shape and grow in the mouth of humans and animals?

Background

Topic: Bacterial Morphology and Identification

This question tests your ability to use bacterial characteristics to identify a specific genus or species.

Key Terms:

Gram-positive: Bacteria that retain the crystal violet stain in the Gram stain procedure.
Facultative anaerobe: Can grow with or without oxygen.
Branching filaments: Bacteria that grow in a filamentous, branching pattern.
Club-shaped: Cells with a thickened end.

Step-by-Step Guidance

List bacteria that are Gram-positive and facultative anaerobes.
Consider which of these grow as branching filaments and have a club shape.
Recall which bacteria are commonly found in the oral cavity of humans and animals.
Narrow down your options based on all these characteristics.

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Q7. How do most pathogens that gain access through unbroken skin enter the body?

Background

Topic: Pathogenesis and Portals of Entry

This question tests your understanding of how pathogens can bypass the skin barrier, which is usually an effective defense.

Key Terms:

Unbroken skin: Intact skin without cuts or abrasions.
Parenteral route: Entry through breaks in the skin or mucous membranes, often via injections, bites, or wounds.

Step-by-Step Guidance

Recall the protective role of unbroken skin against microbial invasion.
Think about exceptions—how can pathogens still enter if the skin is unbroken?
Consider alternative routes such as hair follicles, sweat glands, or via vectors (e.g., insect bites).

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Q8. Which bacteria is the causative agent of tuberculosis?

Background

Topic: Infectious Diseases

This question tests your knowledge of the bacterial species responsible for tuberculosis.

Key Terms:

Tuberculosis (TB): A chronic infectious disease primarily affecting the lungs.
Causative agent: The specific microorganism that causes a disease.

Step-by-Step Guidance

Recall the genus and species name of the bacterium that causes tuberculosis.
Think about the characteristics of this bacterium (e.g., acid-fast, slow-growing).
Consider how this bacterium is transmitted and its significance in public health.

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Q9. Which bacteria is the causative agent of stomach ulcers?

Background

Topic: Infectious Diseases

This question tests your knowledge of the bacterial species linked to peptic ulcers in the stomach.

Key Terms:

Stomach ulcer (peptic ulcer): A sore in the lining of the stomach.
Causative agent: The microorganism responsible for the disease.

Step-by-Step Guidance

Recall the discovery that linked a specific bacterium to stomach ulcers.
Think about the characteristics of this bacterium (e.g., spiral-shaped, urease positive).
Consider how this bacterium survives in the acidic environment of the stomach.

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Q10. Do semisynthetic penicillins affect eukaryotic cells?

Background

Topic: Antibiotics and Selective Toxicity

This question tests your understanding of how antibiotics like penicillins target bacterial cells versus eukaryotic cells.

Key Terms:

Semisynthetic penicillins: Modified forms of penicillin designed to overcome resistance or broaden the spectrum.
Eukaryotic cells: Cells with a nucleus, such as human, animal, and fungal cells.
Selective toxicity: The ability of a drug to target microbial cells without harming host cells.

Step-by-Step Guidance

Recall the mechanism of action of penicillins (inhibition of cell wall synthesis).
Consider whether eukaryotic cells have the same cell wall structure as bacteria.
Think about why penicillins are generally safe for human use.

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Q11. Do Gram + or Gram – cells have an LPS layer?

Background

Topic: Bacterial Cell Wall Structure

This question tests your knowledge of the differences between Gram-positive and Gram-negative bacterial cell walls, specifically regarding the presence of lipopolysaccharide (LPS).

Key Terms:

Gram-positive bacteria: Thick peptidoglycan layer, no outer membrane.
Gram-negative bacteria: Thin peptidoglycan layer, outer membrane containing LPS.
LPS (lipopolysaccharide): A molecule found in the outer membrane of certain bacteria.

Step-by-Step Guidance

Recall the structural differences between Gram-positive and Gram-negative bacteria.
Identify which type has an outer membrane and what is found in that membrane.
Determine which group contains LPS and what its function is.

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Q12. What part of Gram – cells produce endotoxins?

Background

Topic: Bacterial Toxins

This question tests your understanding of endotoxins and their origin in Gram-negative bacteria.

Key Terms:

Endotoxin: A toxin that is a structural component of the bacterial cell wall, specifically LPS.
Gram-negative bacteria: Bacteria with an outer membrane containing LPS.

Step-by-Step Guidance

Recall what endotoxins are and where they are located in Gram-negative bacteria.
Identify the specific part of the cell that contains endotoxins.
Consider how endotoxins are released and their effects on the host.

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Q13. Would an antibiotic that binds between adjacent G-C pairs affect transcription or translation?

Background

Topic: Mechanisms of Antibiotic Action

This question tests your understanding of how antibiotics interact with genetic material and which cellular processes they might disrupt.

Key Terms:

G-C pairs: Guanine-cytosine base pairs in DNA.
Transcription: The process of copying DNA into RNA.
Translation: The process of synthesizing proteins from mRNA.

Step-by-Step Guidance

Recall what happens during transcription and translation and where these processes occur.
Consider what would happen if an antibiotic binds to DNA between G-C pairs.
Determine which process (transcription or translation) would be directly affected by interference with DNA structure.

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Q14. How can the overuse of antibiotics lead to antibiotic resistance?

Background

Topic: Antibiotic Resistance

This question tests your understanding of the mechanisms by which bacteria develop resistance to antibiotics and the role of antibiotic overuse.

Key Terms:

Antibiotic resistance: The ability of bacteria to survive and multiply despite the presence of antibiotics.
Selective pressure: Environmental factors that favor certain traits (e.g., resistance genes).

Step-by-Step Guidance

Recall how antibiotics kill susceptible bacteria but may leave resistant ones alive.
Consider how overuse or misuse of antibiotics increases selective pressure for resistant strains.
Think about how resistance genes can spread among bacterial populations.

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Q15. Are viral spikes found only on non-enveloped viruses?

Background

Topic: Viral Structure

This question tests your understanding of the structure of viruses, specifically the presence and location of spike proteins.

Key Terms:

Viral spikes: Glycoproteins that protrude from the surface of a virus and are involved in host cell attachment.
Enveloped virus: Virus with a lipid membrane surrounding its capsid.
Non-enveloped virus: Virus lacking a lipid envelope.

Step-by-Step Guidance

Recall the structure of enveloped and non-enveloped viruses.
Consider where spike proteins are located in both types of viruses.
Determine whether spikes are exclusive to one type or found in both.

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Q16. Is Chlamydia trachomatis a virus?

Background

Topic: Microbial Classification

This question tests your ability to classify Chlamydia trachomatis as a bacterium or a virus.

Key Terms:

Chlamydia trachomatis: A microorganism that causes chlamydia infections in humans.
Bacterium vs. virus: Bacteria are prokaryotic cells; viruses are acellular infectious agents.

Step-by-Step Guidance

Recall the characteristics of Chlamydia trachomatis (e.g., cell structure, replication).
Compare these characteristics to those of viruses.
Determine whether Chlamydia trachomatis fits the definition of a bacterium or a virus.

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Q17. What is a prion?

Background

Topic: Infectious Agents

This question tests your understanding of prions and how they differ from other infectious agents.

Key Terms:

Prion: An infectious protein that can cause disease by inducing abnormal folding of normal proteins.
Proteinaceous infectious particle: The origin of the term "prion."

Step-by-Step Guidance

Recall what prions are made of and how they differ from viruses and bacteria.
Think about diseases caused by prions (e.g., mad cow disease, Creutzfeldt-Jakob disease).
Consider how prions replicate and spread disease without nucleic acids.

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Q18. What is a viroid?

Background

Topic: Infectious Agents

This question tests your understanding of viroids and how they differ from viruses and prions.

Key Terms:

Viroid: A small, circular RNA molecule that infects plants.
Virus vs. viroid: Viruses have a protein coat; viroids do not.

Step-by-Step Guidance

Recall the structure and composition of viroids.
Compare viroids to viruses and prions in terms of structure and host range.
Consider the types of diseases caused by viroids.

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Q19. Do antiviral drugs target viral processes that occur during viral infection?

Background

Topic: Antiviral Therapy

This question tests your understanding of how antiviral drugs work and what processes they target.

Key Terms:

Antiviral drug: A medication that inhibits the replication or function of viruses.
Viral processes: Steps in the viral life cycle, such as entry, replication, assembly, and release.

Step-by-Step Guidance

Recall the main steps in the viral life cycle.
Consider which steps are targeted by antiviral drugs (e.g., reverse transcription, protease activity).
Think about whether these drugs affect host processes or are specific to viral processes.

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Q20. What’s the most frequently used portal of entry for pathogens?

Background

Topic: Pathogenesis

This question tests your knowledge of the most common routes by which pathogens enter the human body.

Key Terms:

Portal of entry: The site through which pathogens gain access to the body.
Mucous membranes: Linings of body cavities open to the environment (e.g., respiratory, gastrointestinal tracts).

Step-by-Step Guidance

List the main portals of entry for pathogens (e.g., skin, mucous membranes, parenteral route).
Consider which portal is most commonly used based on exposure and susceptibility.
Think about examples of diseases and how their pathogens enter the body.

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Q21. What is lysogeny?

Background

Topic: Viral Life Cycles

This question tests your understanding of the lysogenic cycle in bacteriophages and how it differs from the lytic cycle.

Key Terms:

Lysogeny: A state in which a bacteriophage genome integrates into the host bacterial genome and replicates along with it without causing immediate lysis.
Prophage: The integrated phage DNA.

Step-by-Step Guidance

Recall the two main life cycles of bacteriophages: lytic and lysogenic.
Describe what happens to the phage DNA during lysogeny.
Consider the implications of lysogeny for the host bacterium and the phage.

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Q22. What’s the genome of Covid-19 composed of?

Background

Topic: Viral Genetics

This question tests your knowledge of the type of genetic material found in SARS-CoV-2, the virus that causes COVID-19.

Key Terms:

Genome: The complete set of genetic material in an organism or virus.
RNA virus: A virus with RNA as its genetic material.

Step-by-Step Guidance

Recall the classification of SARS-CoV-2 (family Coronaviridae).
Identify whether its genome is composed of DNA or RNA.
Consider whether the RNA is single-stranded or double-stranded, and if it is positive or negative sense.

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Q23. Is phage therapy an antiviral or antibacterial treatment?

Background

Topic: Alternative Therapies

This question tests your understanding of phage therapy and what types of infections it targets.

Key Terms:

Phage therapy: The use of bacteriophages to treat bacterial infections.
Bacteriophage: A virus that infects bacteria.

Step-by-Step Guidance

Recall what bacteriophages are and what organisms they infect.
Consider whether phage therapy is used to treat viral or bacterial infections.
Think about the advantages and limitations of phage therapy compared to antibiotics.

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Q24. Are viruses the only known infectious agents that are obligatory intracellular parasites?

Background

Topic: Infectious Agents

This question tests your understanding of what it means to be an obligate intracellular parasite and which agents fit this definition.

Key Terms:

Obligate intracellular parasite: An organism or agent that can only reproduce inside the cells of a host.
Examples: Viruses, some bacteria (e.g., Chlamydia), some protozoa.

Step-by-Step Guidance

Recall the definition of an obligate intracellular parasite.
List other infectious agents besides viruses that require a host cell for replication.
Consider whether viruses are unique in this requirement.

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Q25. Are viruses cultured in culture media?

Background

Topic: Cultivation of Microorganisms

This question tests your understanding of how viruses are grown in the laboratory compared to bacteria and fungi.

Key Terms:

Culture media: Nutrient-rich substances used to grow microorganisms in the lab.
Obligate intracellular parasite: Requires living cells to replicate.

Step-by-Step Guidance

Recall how bacteria and fungi are typically cultured in the lab.
Consider whether viruses can replicate in the same way or require living host cells.
Think about the methods used to culture viruses (e.g., cell cultures, embryonated eggs).

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Q26. How are endotoxins produced and how do they affect the body?

Background

Topic: Bacterial Toxins and Pathogenesis

This question tests your understanding of the origin and effects of endotoxins in Gram-negative bacterial infections.

Key Terms:

Endotoxin: Lipopolysaccharide (LPS) component of the outer membrane of Gram-negative bacteria.
Pathogenesis: The process by which disease develops.

Step-by-Step Guidance

Recall where endotoxins are located in Gram-negative bacteria.
Describe how endotoxins are released (e.g., during bacterial cell death or lysis).
Consider the effects of endotoxins on the human body (e.g., fever, shock).

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Q27. Why are viruses considered infectious "particles" on the borderline between living and non-living?

Background

Topic: Nature of Viruses

This question tests your understanding of the characteristics of viruses and why they are not classified as living organisms.

Key Terms:

Virus: An acellular infectious agent.
Living vs. non-living: Criteria for life include metabolism, growth, and reproduction.

Step-by-Step Guidance

Recall the characteristics that define living organisms.
Compare these characteristics to those of viruses (e.g., lack of metabolism, dependence on host cells for replication).
Consider why viruses are described as "particles" and not cells.