Microbiology

Classifying Life

1. Q: What are the main differences between prokaryotic and eukaryotic cells?
   A: Prokaryotic cells lack a nucleus and membrane-bound organelles, while eukaryotic cells have both.

2. Q: What is the Endosymbiotic Theory?
   A: It suggests that mitochondria and chloroplasts originated from free-living bacteria engulfed by an ancestral eukaryotic cell.

Structure of Prokaryotic and Eukaryotic Cells

3. Q: What is the function of the bacterial cell wall?
   A: It provides structure, protection, and prevents osmotic lysis.

4. Q: What is the difference between Gram-positive and Gram-negative bacteria?
   A: Gram-positive have a thick peptidoglycan layer and stain purple; Gram-negative have a thin peptidoglycan layer, an outer membrane, and stain pink.

5. Q: What are fimbriae and pili?
   A: Fimbriae help bacteria attach to surfaces, while pili are used for conjugation (DNA transfer).

Microbial Genetics

6. Q: What is the difference between genotype and phenotype in bacteria?
   A: Genotype is the genetic makeup, while phenotype is the observable characteristics.

7. Q: What are transposons?
   A: "Jumping genes" that can move between DNA molecules, contributing to genetic variation and antibiotic resistance.

8. Q: What are operons, and how do they regulate bacterial gene expression?
   A: Operons are clusters of genes regulated together, such as the lac operon (controls lactose metabolism).

Viral Structure, Classification, and Replication

9. Q: What is the difference between enveloped and non-enveloped viruses?
   A: Enveloped viruses have a lipid membrane, while non-enveloped viruses lack one and are generally more resistant to environmental factors.

10. Q: What are the five steps of viral replication?
    A: Attachment, penetration, biosynthesis, assembly, release.

11. Q: What is the role of reverse transcriptase in retroviruses?
    A: It converts viral RNA into DNA, allowing integration into the host genome (e.g., HIV).

Growing, Staining, Viewing, and Identifying Microbes

12. Q: What is selective media?
    A: A type of growth medium that inhibits certain microbes while allowing others to grow (e.g., MacConkey agar for Gram-negative bacteria).

13. Q: What is differential media?
    A: A medium that differentiates between microbes based on biochemical reactions (e.g., blood agar for hemolysis).

14. Q: What type of staining is used for Mycobacterium species?
    A: Acid-fast staining, due to the waxy mycolic acid in the cell wall.

Microbial Growth and Prevention Strategies

15. Q: What are obligate aerobes, obligate anaerobes, and facultative anaerobes?
    A: Obligate aerobes need oxygen, obligate anaerobes cannot tolerate oxygen, and facultative anaerobes can grow with or without oxygen.

16. Q: What is the difference between bacteriostatic and bactericidal agents?
    A: Bacteriostatic agents inhibit growth, while bactericidal agents kill bacteria.

17. Q: What is pasteurization?
    A: A process that reduces microbial load in liquids using mild heat (e.g., 72°C for 15 seconds).

Metabolic Pathways and Microbial Identification

18. Q: What is the function of the electron transport chain in bacterial metabolism?
    A: It generates ATP through oxidative phosphorylation.

19. Q: What test is used to detect bacterial fermentation of carbohydrates?
    A: The phenol red broth test, which changes color based on acid production.

20. Q: How do bacteria use nitrate as a terminal electron acceptor?
    A: In anaerobic respiration, some bacteria reduce nitrate (NO₃⁻) to nitrogen gas (N₂) instead of using oxygen.

Principles of Infectious Disease and Epidemiology

21. Q: What is the difference between a reservoir and a vector in disease transmission?
    A: A reservoir is the primary habitat of a pathogen, while a vector is an organism (like mosquitoes) that transmits the pathogen.

22. Q: What are Koch’s postulates?
    A: Criteria used to establish a microbe as the cause of a disease, including isolation and reinfection experiments.

23. Q: What is an example of a nosocomial infection?
    A: Hospital-acquired infections like MRSA or C. difficile.

Host-Microbe Interactions & Infection Control

24. Q: What are virulence factors?
    A: Traits that enhance a microbe’s ability to cause disease, such as toxins, adhesins, and capsules.

25. Q: What is the difference between endotoxins and exotoxins?
    A: Endotoxins (LPS) are found in Gram-negative bacteria and released upon cell death, while exotoxins are secreted proteins that cause damage.

26. Q: What is the purpose of an autoclave in infection control?
    A: It uses high-pressure steam to sterilize equipment and kill all microbes, including spores.

Immune System and Infectious Disease

27. Q: What is the function of natural killer (NK) cells?
    A: They kill virus-infected and cancerous cells by inducing apoptosis.

28. Q: What are the four main signs of inflammation?
    A: Redness, heat, swelling, pain.

29. Q: What is the function of complement proteins in immunity?
    A: They enhance phagocytosis, lyse bacteria, and promote inflammation.

Vaccines and Diagnostics

30. Q: What is herd immunity?
    A: When a large portion of a population is vaccinated, reducing the spread of disease.

31. Q: How do monoclonal antibodies work in diagnostics?
    A: They specifically bind to pathogens or antigens, aiding in disease detection (e.g., pregnancy tests, COVID-19 rapid tests).

32. Q: What is the difference between active and passive immunity?
    A: Active immunity develops from infection or vaccination; passive immunity is transferred from another source (e.g., maternal antibodies).

Antimicrobial Drugs and Resistance

33. Q: What is the mechanism of action of β-lactam antibiotics?
    A: They inhibit bacterial cell wall synthesis (e.g., penicillin).

34. Q: How do fluoroquinolones kill bacteria?
    A: They inhibit DNA gyrase, preventing bacterial DNA replication.

35. Q: What is the difference between broad-spectrum and narrow-spectrum antibiotics?
    A: Broad-spectrum antibiotics target a wide range of bacteria, while narrow-spectrum antibiotics target specific types.

36. Q: How does antibiotic resistance develop?
    A: Through genetic mutations, horizontal gene transfer, and selective pressure from antibiotic overuse.

Classifying Life

1. Q: What are the three domains of life?
   A: Bacteria, Archaea, Eukarya.

2. Q: What characteristics differentiate Bacteria and Archaea?
   A: Bacteria have peptidoglycan in their cell walls, while Archaea lack it and often live in extreme environments.

Structure of Prokaryotic and Eukaryotic Cells

3. Q: What structures are unique to prokaryotic cells?
   A: Nucleoid (no nucleus), circular DNA, peptidoglycan cell wall (in bacteria), and plasmids.

4. Q: What structures are unique to eukaryotic cells?
   A: Nucleus, membrane-bound organelles (mitochondria, ER, Golgi apparatus), and linear DNA.

Microbial Genetics

5. Q: What is the function of plasmids in bacteria?
   A: They carry genes for antibiotic resistance, virulence, and other survival traits.

6. Q: What are the three mechanisms of horizontal gene transfer in bacteria?
   A: Transformation, transduction, and conjugation.

Viral Structure, Classification, and Replication

7. Q: What are the basic components of a virus?
   A: Nucleic acid (DNA or RNA), protein capsid, and sometimes a lipid envelope.

8. Q: What are the main viral replication pathways?
   A: Lytic cycle (kills host cell) and lysogenic cycle (integrates into host genome).

Growing, Staining, Viewing, and Identifying Microbes

9. Q: What is the purpose of Gram staining?
   A: To differentiate bacteria into Gram-positive (thick peptidoglycan, purple) and Gram-negative (thin peptidoglycan, pink).

10. Q: What type of microscopy is best for viewing viruses?
    A: Electron microscopy.

Microbial Growth and Prevention Strategies

11. Q: What are the four phases of bacterial growth?
    A: Lag, log (exponential), stationary, death.

12. Q: Name two physical and two chemical methods of microbial control.
    A: Physical: Heat, radiation. Chemical: Disinfectants, antiseptics.

Metabolic Pathways and Microbial Identification

13. Q: How is metabolism used to identify microbes?
    A: Different bacteria have unique metabolic pathways (e.g., lactose fermentation in MacConkey agar).

14. Q: What are the main types of microbial metabolism?
    A: Aerobic respiration, anaerobic respiration, fermentation.

Principles of Infectious Disease and Epidemiology

15. Q: What is the difference between endemic, epidemic, and pandemic diseases?
    A: Endemic: Constant presence in a population. Epidemic: Sudden outbreak. Pandemic: Worldwide spread.

16. Q: What is the difference between incidence and prevalence?
    A: Incidence: New cases over time. Prevalence: Total cases at a given time.

Host-Microbe Interactions & Infection Control

17. Q: What is the difference between commensalism, mutualism, and parasitism?
    A: Commensalism: One benefits, the other is unaffected. Mutualism: Both benefit. Parasitism: One benefits, the other is harmed.

18. Q: What are the four biosafety levels (BSL)?
    A: BSL-1: Minimal risk. BSL-2: Moderate risk (HIV). BSL-3: High risk (TB). BSL-4: Extreme risk (Ebola).

Immune System and Infectious Disease

19. Q: What are the main components of innate immunity?
    A: Skin, mucous membranes, phagocytes, fever, inflammation.

20. Q: What are the main cells involved in adaptive immunity?
    A: B cells (antibody production) and T cells (cell-mediated immunity).

Vaccines and Diagnostics

21. Q: What are the main types of vaccines?
    A: Live attenuated, inactivated, subunit, toxoid, mRNA.

22. Q: How do PCR and ELISA help in diagnosing infections?
    A: PCR detects DNA/RNA, ELISA detects antigens or antibodies.

Antimicrobial Drugs and Resistance

23. Q: How do antibiotics work?
    A: They target bacterial structures (cell wall, ribosomes, DNA replication).

Q: What are common mechanisms of antibiotic resistance?
A: Efflux pumps, enzyme production (e.g., β-lactamase), target modification.