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.
16S rRNA gene: Commonly used for bacterial classification.

Step-by-Step Guidance

Understand that rRNA genes, especially 16S rRNA in prokaryotes, are present in all organisms and evolve slowly, making them useful for comparing evolutionary relationships.
Scientists sequence the rRNA genes from different organisms and compare the sequences to identify similarities and differences.
Organisms with more similar rRNA sequences are considered more closely related.
These comparisons are used to construct phylogenetic trees, which help classify organisms into domains, kingdoms, 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 characteristics that define cellular life.
Consider the structural components of viruses and whether they contain the features of cells (such as cytoplasm, organelles, or a plasma membrane).
Think about how viruses replicate and whether they carry out cellular processes independently.

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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 capabilities, often involving enzymes.

Key Terms:

Biochemical test: Laboratory tests that detect metabolic activities of microbes.
Enzyme: A protein that catalyzes biochemical reactions.

Step-by-Step Guidance

Recall examples of biochemical tests (e.g., catalase test, oxidase test, fermentation tests).
Consider what these tests detect—are they looking for the presence of specific enzymes or the products of enzymatic reactions?
Think about how the results of these tests help identify microorganisms.

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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.
Blood: The circulatory fluid in the body.

Step-by-Step Guidance

List the common portals of entry for pathogens (e.g., mucous membranes, skin, respiratory tract, gastrointestinal tract).
Consider whether blood is typically an initial entry point or if it is more often a route for dissemination after entry.
Think about examples where pathogens might directly enter the bloodstream (e.g., via insect bites or needles).

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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, others have RNA.

Step-by-Step Guidance

Recall the typical genetic material found in bacteria.
Compare this to viruses, which can have either DNA or RNA genomes.
Consider whether any known bacteria have an RNA genome.

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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 asks you to identify a bacterium based on its Gram reaction, oxygen requirements, growth pattern, shape, and habitat.

Key Terms:

Gram-positive: Bacteria that retain the crystal violet stain.
Facultative anaerobe: Can grow with or without oxygen.
Branching filaments: Growth pattern resembling branches.
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.
Think about bacteria commonly found in the oral cavity of humans and animals.
Narrow down to the genus or species that fits 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.
Pathogen entry: Mechanisms by which microbes enter the body.

Step-by-Step Guidance

Recall the protective role of unbroken skin against microbial invasion.
Consider alternative routes pathogens might use to bypass the skin (e.g., hair follicles, sweat glands, insect vectors).
Think about examples of diseases where pathogens enter through these routes.

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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 TB.
Consider the characteristics of this bacterium (e.g., acid-fast, slow-growing).
Think about 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: 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 with broader activity.
Eukaryotic cells: Cells with a nucleus (e.g., human cells).
Selective toxicity: The ability of a drug to target microbes 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: Thick peptidoglycan layer, no outer membrane.
Gram-negative: Thin peptidoglycan layer, outer membrane with LPS.
LPS (lipopolysaccharide): A molecule found in the outer membrane of some bacteria.

Step-by-Step Guidance

Recall the structural differences between Gram-positive and Gram-negative bacteria.
Identify which type has an outer membrane containing LPS.
Consider the role of LPS in bacterial pathogenicity.

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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 part of the outer membrane of Gram-negative bacteria.
LPS (lipopolysaccharide): The molecule responsible for endotoxin activity.

Step-by-Step Guidance

Recall the structure of the Gram-negative cell envelope.
Identify which component of the cell envelope is responsible for endotoxin activity.
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 can interfere with genetic processes by binding to DNA or RNA.

Key Terms:

G-C pairs: Guanine-cytosine base pairs in DNA.
Transcription: Synthesis of RNA from a DNA template.
Translation: Synthesis of protein from an mRNA template.

Step-by-Step Guidance

Recall the processes of transcription and translation and where they occur in the cell.
Consider what would happen if an antibiotic binds to DNA at G-C pairs—would this block RNA polymerase or ribosomes?
Think about which process (transcription or translation) directly involves DNA as a template.

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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, especially due to misuse or 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.

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 the role of genetic mutations and horizontal gene transfer in spreading resistance.

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

Background

Topic: Viral Structure

This question tests your knowledge of the structural features of viruses, specifically the presence and location of spikes (glycoproteins).

Key Terms:

Viral spikes: Protein structures that project from the surface of a virus.
Enveloped virus: Virus with a lipid membrane surrounding the capsid.
Non-enveloped virus: Virus lacking a lipid envelope.

Step-by-Step Guidance

Recall the structure of enveloped and non-enveloped viruses.
Consider where spikes are located in each type of virus.
Think about the function of spikes in viral attachment and entry.

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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.
Bacterium vs. virus: Differences in structure, replication, and classification.

Step-by-Step Guidance

Recall the characteristics of bacteria and viruses.
Consider the cellular structure, genome type, and replication method of Chlamydia trachomatis.
Think about how this organism is treated and classified in microbiology.

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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 like viruses and bacteria.

Key Terms:

Prion: An infectious protein that causes neurodegenerative diseases.
Proteinaceous infectious particle: The origin of the term "prion".

Step-by-Step Guidance

Recall the structure and composition of prions.
Consider how prions cause disease compared to viruses and bacteria.
Think about examples of prion diseases.

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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 other pathogens.

Key Terms:

Viroid: A small, circular RNA molecule that infects plants.
Virus vs. viroid: Differences in structure and host range.

Step-by-Step Guidance

Recall the structure and genetic material of viroids.
Consider how viroids replicate and cause disease.
Think about the types of organisms viroids infect.

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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: Medication that inhibits the replication of viruses.
Viral processes: Steps in the viral life cycle (e.g., entry, replication, assembly, release).

Step-by-Step Guidance

Recall the main stages of the viral life cycle.
Consider which stages are targeted by antiviral drugs (e.g., entry inhibitors, protease inhibitors).
Think about why targeting viral processes is important for effective treatment.

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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 common routes by which pathogens enter the human body.

Key Terms:

Portal of entry: The site through which pathogens enter the host.
Mucous membranes: Lining of body cavities open to the environment.

Step-by-Step Guidance

List the main portals of entry (e.g., respiratory tract, gastrointestinal tract, skin).
Consider which portal is most commonly used by pathogens based on exposure and susceptibility.
Think about examples of diseases that enter through each portal.

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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: Integration of phage DNA into the host bacterial genome.
Prophage: Phage DNA that is integrated into the host genome.

Step-by-Step Guidance

Recall the steps of the lysogenic cycle and how it differs from the lytic cycle.
Consider the consequences of lysogeny for the host bacterium and the phage.
Think about examples of phages that undergo lysogeny.

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

Step-by-Step Guidance

Recall the classification of coronaviruses based on their genome type.
Consider whether the genome is single-stranded or double-stranded, and if it is positive-sense or negative-sense.
Think about how this genome type affects replication and detection methods.

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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 infect and destroy.
Consider whether phage therapy is used against bacterial or viral 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 infectious agents fit this definition.

Key Terms:

Obligate intracellular parasite: An organism that can only reproduce inside the cells of a host.
Examples: Viruses, some bacteria, some protozoa.

Step-by-Step Guidance

Recall the definition of obligate intracellular parasites.
List other infectious agents besides viruses that require a host cell for replication.
Consider examples such as Chlamydia and Rickettsia.

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Q25. Are viruses cultured in culture media?

Background

Topic: Cultivation of Microorganisms

This question tests your understanding of the requirements for growing viruses in the laboratory.

Key Terms:

Culture media: Nutrient solutions used to grow microorganisms.
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 absence of 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

This question tests your understanding of the production and effects of endotoxins from Gram-negative bacteria.

Key Terms:

Endotoxin: Lipid A component of LPS in Gram-negative bacteria.
Pathophysiology: The effects of endotoxins on the host (e.g., fever, shock).

Step-by-Step Guidance

Recall where endotoxins are located in Gram-negative bacteria.
Consider how endotoxins are released (e.g., during cell lysis).
Think about the effects of endotoxins on the human body (e.g., immune response, fever, septic 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 unique characteristics of viruses and why they are not classified as fully living organisms.

Key Terms:

Virus: Infectious agent with genetic material and a protein coat.
Living vs. non-living: Criteria for life (e.g., metabolism, reproduction, response to stimuli).

Step-by-Step Guidance

Recall the characteristics that define living organisms.
Consider which of these characteristics viruses possess and which they lack.
Think about why viruses are described as "particles" and not cells.