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MICROBIOLOGY MIDTERM EXAM JERSEY COLLEGE VERSION 2 QUESTIONS AND CORRECT ANSWERS (VERIFIED ANSWERS) PLUS RATIONALES 2025
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1. What structure do bacteria use for motility? A. Capsule B. Ribosome C. Flagellum D. Pili Flagella are tail-like structures that rotate to propel bacteria through their environment. 2. Which of the following is not a function of the bacterial cell wall? A. Maintains cell shape B. Protein synthesis C. Prevents osmotic lysis
D. Protects against environmental stress Protein synthesis occurs in the ribosomes, not in the cell wall.
3. Which of the following is a gram-positive bacterium? A. Escherichia coli B. Neisseria gonorrhoeae C. Staphylococcus aureus D. Salmonella typhi Staphylococcus aureus has a thick peptidoglycan cell wall, staining purple during Gram staining. 4. What is the function of plasmids in bacteria? A. Respiration B. Carry non-essential genes such as antibiotic resistance C. Protein synthesis D. Energy production Plasmids are small DNA molecules that often carry genes for antibiotic resistance or toxins. 5. Which of the following is considered an obligate intracellular parasite? A. Bacteria B. Viruses C. Fungi D. Protozoa Viruses must enter a host cell to replicate and cannot reproduce independently.
C. Log (exponential) phase D. Death phase During the log phase, bacteria multiply at an exponential rate.
10. What type of organism can grow with or without oxygen? A. Obligate aerobe B. Facultative anaerobe C. Microaerophile D. Obligate anaerobe Facultative anaerobes can adjust their metabolism to use oxygen when available. 11. Which of the following is a characteristic of endotoxins? A. Secreted by live cells B. Found in Gram-negative bacteria C. Composed of proteins D. Produced by Gram-positive bacteria only Endotoxins are part of the lipopolysaccharide in Gram-negative outer membranes. 12. The term “nosocomial infection” refers to an infection: A. Caused by antibiotics B. Acquired in a healthcare setting C. From contaminated food D. Present at birth
Nosocomial infections are those that develop in hospitals or clinical settings.
13. Which of the following organisms uses budding as a form of reproduction? A. Bacteria B. Yeast C. Viruses D. Protozoa Yeast, a type of fungus, reproduces by budding, where a new cell grows from a parent. 14. What is the purpose of Koch’s postulates? A. Identify DNA mutations B. Create vaccines C. Prove a microbe causes disease D. Determine gram type Koch’s postulates are used to establish the link between a microbe and a disease. 15. Which structure helps bacteria adhere to surfaces? A. Capsule B. Flagella C. Fimbriae D. Ribosome
Reverse transcriptase synthesizes DNA from an RNA template in retroviruses.
19. Which of the following is a helminth? A. Candida albicans B. Taenia solium C. Giardia lamblia D. Plasmodium falciparum Taenia solium is a parasitic tapeworm, classified as a helminth. 20. Which of the following is most effective at killing endospores? A. Boiling B. Refrigeration C. Autoclaving D. Filtration Autoclaving uses pressurized steam at high temperature, which destroys endospores. 21. What is the main target of penicillin in bacterial cells? A. DNA replication B. Peptidoglycan synthesis C. Protein synthesis D. ATP production Penicillin interferes with the synthesis of peptidoglycan in bacterial cell walls.
22. Which type of virus immediately begins replication upon entering a host cell? A. Lysogenic B. Lytic C. Retrovirus D. Latent Lytic viruses hijack the host cell machinery to produce viral components immediately. 23. What type of medium distinguishes between different organisms based on biological characteristics? A. Enriched B. Selective C. Differential D. Complex Differential media allows visualization of metabolic differences between organisms. 24. Which method is best to isolate pure bacterial colonies? A. Broth culture B. Streak plate method C. Pour plate D. Slant tube Streak plating spreads bacteria on agar to separate individual colonies.
B. Methylene blue C. Crystal violet D. Carbol fuchsin Crystal violet is the primary stain that binds to Gram-positive cell walls.
29. A microorganism that grows best at moderate temperatures is classified as a: A. Thermophile B. Mesophile C. Psychrophile D. Halophile Mesophiles prefer temperatures around 20–45°C, including human body temperature. 30. What organism causes malaria? A. Trypanosoma B. Toxoplasma C. Plasmodium D. Giardia Plasmodium species are protozoa that cause malaria in humans. 31. What is the mode of action of tetracycline antibiotics? A. Inhibit DNA synthesis B. Inhibit protein synthesis C. Disrupt cell wall
D. Inhibit folic acid synthesis Tetracyclines bind to the 30S ribosomal subunit, halting protein production.
32. What is the reservoir for Clostridium tetani? A. Insects B. Water C. Soil D. Humans Clostridium tetani spores are found in soil and can infect wounds. 33. Which of the following is used to preserve microbial cultures long- term? A. Room temperature B. Refrigerator C. Autoclave D. Deep freezing Deep freezing maintains cultures for long-term storage without damaging cells. 34. Which bacteria can survive without oxygen but grow better with it? A. Obligate anaerobe B. Facultative anaerobe C. Microaerophile D. Aerotolerant anaerobe Facultative anaerobes can grow in both aerobic and anaerobic conditions.
C. Tinea capitis D. Tinea cruris Tinea capitis is a ringworm infection of the scalp.
39. What is the mode of transmission for Hepatitis B? A. Fecal-oral B. Inhalation C. Blood and body fluids D. Vector-borne Hepatitis B is primarily transmitted through blood, sexual contact, or from mother to child. 40. What is an example of a prion disease? A. Polio B. Creutzfeldt-Jakob disease C. Hepatitis C D. Measles Prion diseases are caused by misfolded proteins and affect the nervous system. 41. The term “bacteriostatic” means: A. Kills bacteria B. Inhibits bacterial growth C. Prevents viral replication D. Kills fungi
Bacteriostatic agents stop bacterial growth, but don’t necessarily kill the organisms.
42. A virus that infects bacteria is called a: A. Retrovirus B. Provirus C. Bacteriophage D. Lytic virus Bacteriophages infect bacterial cells and are used in genetic studies. 43. Which microbe is the causative agent of Lyme disease? A. Rickettsia rickettsii B. Borrelia burgdorferi C. Treponema pallidum D. Yersinia pestis Borrelia burgdorferi is a spirochete transmitted by ticks. 44. Which organ system is most affected by Cryptococcus neoformans? A. Skin B. Central nervous system C. Digestive tract D. Muscular system Cryptococcus neoformans can cause fungal meningitis, especially in immunocompromised patients. 45. What is the purpose of a control in an experiment? A. Speed up the reaction
MIC is the lowest concentration of an antimicrobial that inhibits visible growth.
49. The first antibody produced in response to an infection is: A. IgA B. IgM C. IgE D. IgG IgM is produced first during the primary immune response. 50. Which of the following can form endospores? A. Escherichia coli B. Bacillus subtilis C. Staphylococcus epidermidis D. Lactobacillus Bacillus species produce endospores to survive harsh environments. 51. What type of infection develops rapidly but lasts a short time? A. Chronic B. Acute C. Latent D. Subclinical Acute infections have a sudden onset and typically resolve quickly.
52. Which component of the immune system is responsible for destroying virus-infected cells? A. B cells B. Cytotoxic T cells C. Helper T cells D. Macrophages Cytotoxic T cells kill infected host cells by recognizing viral antigens on their surface. 53. Which of the following bacterial structures is involved in conjugation? A. Capsule B. Flagellum C. Sex pilus D. Fimbriae The sex pilus facilitates the transfer of DNA between bacterial cells during conjugation. 54. The term “vector” refers to: A. An infected animal B. A virus that causes cancer C. An organism that transmits pathogens D. A type of immune cell A vector, such as a mosquito or tick, carries and transmits infectious agents.
B. Artificial active C. Natural passive D. Artificial passive Vaccines stimulate the immune system to create memory cells (artificial active immunity).
59. The function of lysozyme in tears is to: A. Break down proteins B. Damage bacterial cell walls C. Promote inflammation D. Inhibit viral replication Lysozyme breaks down peptidoglycan, especially in Gram-positive bacteria. 60. What is a facultative intracellular pathogen? A. Only survives outside cells B. Always requires a host cell C. Can live both inside and outside host cells D. Cannot replicate Facultative intracellular pathogens, like Salmonella, can adapt to life both inside and outside cells. 61. What is the infectious stage of Giardia lamblia? A. Trophozoite B. Cyst
C. Spore D. Hyphae Giardia cysts are hardy, infectious forms that survive outside the host.
62. What term describes organisms that require high salt concentrations to grow? A. Thermophiles B. Psychrophiles C. Acidophiles D. Halophiles Halophiles thrive in environments with high salt content. 63. Which of the following is a dimorphic fungus? A. Penicillium B. Aspergillus C. Histoplasma capsulatum D. Cryptococcus Dimorphic fungi like Histoplasma exist as molds in the environment and yeasts in tissue. 64. Which organism causes whooping cough? A. Streptococcus pyogenes B. Corynebacterium diphtheriae C. Bordetella pertussis D. Haemophilus influenzae
