Q. A 25-year-old male presents with recurrent respiratory infections. Which immune component is most likely deficient?
A.B cells
B.T cells
C.Complement system
D.Phagocytes
Solution
Recurrent respiratory infections are often associated with B cell deficiencies, leading to inadequate antibody production.
Correct Answer: A — B cells
Q. A 28-year-old woman presents with a sore throat and swollen lymph nodes. A rapid strep test is positive. What is the most likely causative agent?
A.Streptococcus pyogenes
B.Streptococcus pneumoniae
C.Haemophilus influenzae
D.Corynebacterium diphtheriae
Solution
Streptococcus pyogenes is the most common cause of pharyngitis and is detected by rapid strep tests.
Correct Answer: A — Streptococcus pyogenes
Q. A 30-year-old woman develops a urinary tract infection. A urine culture shows the presence of a gram-negative bacillus. Which organism is the most common cause of such infections?
A.Escherichia coli
B.Proteus mirabilis
C.Enterococcus faecalis
D.Klebsiella pneumoniae
Solution
Escherichia coli is the most common cause of urinary tract infections.
Correct Answer: A — Escherichia coli
Q. A 30-year-old woman is diagnosed with systemic lupus erythematosus (SLE). What type of immune response is primarily involved in this autoimmune disease?
A.Innate immune response
B.Humoral immune response
C.Cell-mediated immune response
D.Complement-mediated response
Solution
SLE is characterized by a humoral immune response, particularly the production of autoantibodies.
Correct Answer: B — Humoral immune response
Q. A 45-year-old man presents with fever, cough, and chest pain. A chest X-ray shows a cavitary lesion in the right upper lobe. Which microorganism is most likely responsible for this condition?
A.Streptococcus pneumoniae
B.Mycobacterium tuberculosis
C.Klebsiella pneumoniae
D.Legionella pneumophila
Solution
The cavitary lesion in the right upper lobe is characteristic of pulmonary tuberculosis, which is caused by Mycobacterium tuberculosis.
Correct Answer: B — Mycobacterium tuberculosis
Q. A 50-year-old man presents with fever, night sweats, and weight loss. A biopsy of a lymph node reveals granulomas. Which infectious agent is most likely responsible?
A.Histoplasma capsulatum
B.Mycobacterium tuberculosis
C.Coccidioides immitis
D.Brucella spp.
Solution
Granulomas in the lymph nodes are characteristic of tuberculosis, which is caused by Mycobacterium tuberculosis.
Correct Answer: B — Mycobacterium tuberculosis
Q. A child is brought to the clinic with a rash, fever, and cough. The physician suspects measles. Which vaccine could have prevented this disease?
A.Inactivated polio vaccine
B.MMR vaccine
C.Hepatitis B vaccine
D.Diphtheria-tetanus-pertussis vaccine
Solution
The MMR vaccine (measles, mumps, rubella) is effective in preventing measles.
Correct Answer: B — MMR vaccine
Q. A child receives a measles vaccine. What type of immunity is conferred by this vaccination?
A.Passive immunity
B.Active immunity
C.Innate immunity
D.Natural immunity
Solution
The measles vaccine provides active immunity by stimulating the immune system to produce antibodies.
Correct Answer: B — Active immunity
Q. A culture shows a growth of 1,200 colonies after incubation. If the dilution factor was 1:100, what was the original concentration of bacteria in the sample?
A.120,000 CFU/mL
B.12,000 CFU/mL
C.1,200 CFU/mL
D.120 CFU/mL
Solution
To find the original concentration, multiply the number of colonies by the dilution factor: 1,200 colonies * 100 = 120,000 CFU/mL.
Correct Answer: A — 120,000 CFU/mL
Q. A laboratory technician is exposed to a needle stick injury from a patient with hepatitis B. What is the most appropriate post-exposure prophylaxis?
A.Hepatitis B vaccine
B.Hepatitis A vaccine
C.Intravenous immunoglobulin
D.No treatment necessary
Solution
Post-exposure prophylaxis for hepatitis B includes administering the hepatitis B vaccine.
Correct Answer: A — Hepatitis B vaccine
Q. A laboratory test shows that a patient has a viral load of 5,000 copies/mL. If the treatment reduces the viral load by 80%, what is the new viral load?
A.1,000 copies/mL
B.2,000 copies/mL
C.3,000 copies/mL
D.4,000 copies/mL
Solution
An 80% reduction means that 20% of the original viral load remains. 20% of 5,000 copies/mL is 1,000 copies/mL.
Correct Answer: A — 1,000 copies/mL
Q. A patient develops an allergic reaction after exposure to pollen. Which type of immune response is primarily involved?
A.Cell-mediated immunity
B.Humoral immunity
C.Innate immunity
D.Autoimmunity
Solution
Allergic reactions are primarily mediated by humoral immunity, specifically IgE antibodies.
Correct Answer: B — Humoral immunity
Q. A patient is diagnosed with a bacterial infection and is prescribed antibiotics. If the bacteria have a resistance rate of 25%, what is the probability that a randomly selected bacterium is susceptible to the antibiotic?
A.25%
B.50%
C.75%
D.100%
Solution
If 25% of the bacteria are resistant, then 75% are susceptible to the antibiotic.
Correct Answer: C — 75%
Q. A patient presents with a sudden onset of high fever, chills, and a petechial rash. Blood cultures reveal Neisseria meningitidis. What is the most effective preventive measure?
A.Antibiotic prophylaxis
B.Meningococcal vaccine
C.Isolation of the patient
D.Intravenous immunoglobulin
Solution
The meningococcal vaccine is the most effective preventive measure against Neisseria meningitidis infection.
Correct Answer: B — Meningococcal vaccine
Q. A patient presents with severe diarrhea and dehydration. Stool culture reveals the presence of a toxin-producing organism. Which organism is most likely responsible?
A.Escherichia coli
B.Clostridium difficile
C.Salmonella enterica
D.Vibrio cholerae
Solution
Clostridium difficile is known for causing antibiotic-associated diarrhea and produces toxins that lead to severe gastrointestinal symptoms.
Correct Answer: B — Clostridium difficile
Q. A patient with a history of HIV presents with oral thrush and esophageal pain. What is the most likely causative organism?
A.Candida albicans
B.Aspergillus fumigatus
C.Cryptococcus neoformans
D.Histoplasma capsulatum
Solution
Oral thrush in an immunocompromised patient is most commonly caused by Candida albicans.
Correct Answer: A — Candida albicans
Q. A patient with a history of travel to tropical regions presents with fever, jaundice, and abdominal pain. Which virus is most likely responsible for these symptoms?
A.Hepatitis A virus
B.Hepatitis B virus
C.Dengue virus
D.Yellow fever virus
Solution
Yellow fever virus is endemic in tropical regions and can cause fever, jaundice, and abdominal pain.
Correct Answer: D — Yellow fever virus
Q. A patient with HIV is at risk for opportunistic infections. Which immune cells are primarily affected by the virus?
A.B cells
B.Cytotoxic T cells
C.Helper T cells
D.Natural killer cells
Solution
HIV primarily targets and destroys CD4+ helper T cells, leading to immunodeficiency.
Correct Answer: C — Helper T cells
Q. At what stage does the zygote implant into the uterine wall?
A.Cleavage stage
B.Blastocyst stage
C.Gastrulation stage
D.Neurulation stage
Solution
The zygote implants into the uterine wall during the blastocyst stage, approximately 5-6 days after fertilization.
Correct Answer: B — Blastocyst stage
Q. At what stage of development does the heart begin to beat in a human embryo?
A.2 weeks
B.4 weeks
C.6 weeks
D.8 weeks
Solution
The heart begins to beat around 4 weeks of embryonic development.
Correct Answer: B — 4 weeks
Q. At what stage of development does the neural tube form?
A.Zygote stage
B.Gastrulation
C.Neurulation
D.Organogenesis
Solution
Neurulation is the stage of development where the neural tube, which will develop into the central nervous system, forms.
Correct Answer: C — Neurulation
Q. At what stage of development is the human embryo most susceptible to teratogens?
A.Fertilization
B.First trimester
C.Second trimester
D.Third trimester
Solution
The first trimester is when the embryo is most susceptible to teratogens, as major organs are forming.
Correct Answer: B — First trimester
Q. At what stage of human development does implantation occur?
A.Zygote stage
B.Blastocyst stage
C.Embryonic stage
D.Fetal stage
Solution
Implantation occurs when the blastocyst attaches to the uterine wall, typically around 6-10 days after fertilization.
Correct Answer: B — Blastocyst stage
Q. At what temperature range do most plants grow best?
A.0-10°C
B.10-20°C
C.20-30°C
D.30-40°C
Solution
Most plants grow best in the temperature range of 20-30°C.
Correct Answer: C — 20-30°C
Q. At what week does the heart start to beat in a developing fetus?
A.4 weeks
B.6 weeks
C.8 weeks
D.10 weeks
Solution
The heart starts to beat around 6 weeks of gestation.
Correct Answer: B — 6 weeks
Q. During transcription, which enzyme is responsible for synthesizing RNA from a DNA template?
A.DNA polymerase
B.RNA polymerase
C.Ribosome
D.Ligase
Solution
RNA polymerase is the enzyme that synthesizes RNA by transcribing the DNA template during the process of transcription.
Correct Answer: B — RNA polymerase
Q. During transcription, which enzyme synthesizes RNA from a DNA template?
A.DNA polymerase
B.RNA polymerase
C.Ribosome
D.Ligase
Solution
RNA polymerase is the enzyme responsible for synthesizing RNA from a DNA template during the process of transcription.
Correct Answer: B — RNA polymerase
Q. During which part of the day do plants primarily perform respiration?
A.Daytime only
B.Nighttime only
C.Both day and night
D.Only during photosynthesis
Solution
Plants perform respiration both day and night, although photosynthesis occurs primarily during the day.
Correct Answer: C — Both day and night
Q. During which phase of photosynthesis is carbon dioxide incorporated into organic molecules?
A.Light reactions
B.Calvin cycle
C.Photorespiration
D.Electron transport chain
Solution
Carbon dioxide is incorporated into organic molecules during the Calvin cycle.
Correct Answer: B — Calvin cycle
Q. During which phase of photosynthesis is carbon dioxide utilized?
A.Light reactions
B.Calvin cycle
C.Photorespiration
D.Electron transport chain
Solution
Carbon dioxide is utilized during the Calvin cycle.
