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Which is NOT TRUE:
- A. Defense role of the skin is related to the low pH of the skin surface
- B. Defense role of the skin is related to activity of the skin macrophages
- C. Defense role of the skin is related to secretion
- D. Defense role of skin is related to lysozyme activity
Correct Answer: D
Rationale: The correct answer is D because the defense role of the skin is not related to lysozyme activity. Lysozyme is an enzyme found in tears, saliva, and mucus, not specifically in the skin. The skin's defense role is primarily related to its physical barrier function, low pH creating an acidic environment that inhibits microbial growth, secretion of antimicrobial peptides, and the activity of skin macrophages that phagocytose pathogens. Choices A, B, and C are true statements as they correctly describe different aspects of the skin's defense mechanisms.
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Toxoplasma gondii belongs to which group of eukaryotic organisms?
- A. Algae
- B. Fungi
- C. Protozoans
- D. Helminths
Correct Answer: C
Rationale: Toxoplasma gondii is a protozoan parasite known to cause toxoplasmosis. It belongs to the group of eukaryotic organisms called protozoans because it is a single-celled organism with complex cellular structures. Protozoans are characterized by their ability to move and perform essential functions independently. Algae (choice A) are photosynthetic eukaryotic organisms, fungi (choice B) are non-photosynthetic eukaryotes that include molds and yeasts, and helminths (choice D) are multicellular parasitic worms. Therefore, the correct answer is C because Toxoplasma gondii is a protozoan parasite.
The cell surface of pathogenic gram-negative bacteria can be covered in villi and cilia. What function do these structures have?
- A. RNA exchange between cells
- B. Inhibition of complement activity
- C. Bacterial adhesion to the surface of the host cells, conjugation
- D. Resistance to antibody opsonization
Correct Answer: C
Rationale: The correct answer is C: Bacterial adhesion to the surface of the host cells, conjugation. Villi and cilia on the cell surface of pathogenic bacteria help in bacterial adhesion to host cells, facilitating the process of infection. Conjugation is the transfer of genetic material between bacterial cells, which can be aided by these structures. The other choices are incorrect because RNA exchange between cells (A) is typically facilitated by different structures like pili, inhibition of complement activity (B) is not related to the function of villi and cilia, and resistance to antibody opsonization (D) is usually achieved through other mechanisms such as capsule formation.
Which of the following bacteria is responsible for causing the disease diphtheria?
- A. Bacillus anthracis
- B. Corynebacterium diphtheriae
- C. Streptococcus pneumoniae
- D. Escherichia coli
Correct Answer: B
Rationale: The correct answer is B: Corynebacterium diphtheriae. This bacterium produces a toxin that causes diphtheria. It forms a grayish membrane in the throat, leading to difficulty breathing. Bacillus anthracis (Choice A) causes anthrax, Streptococcus pneumoniae (Choice C) causes pneumonia, and Escherichia coli (Choice D) causes various infections but not diphtheria.
According to their optimal growth temperatures, microorganisms are divided into:
- A. Thermophilic and thermophobic
- B. Psychophilic and psychophobic
- C. Psychophilic, mesophilic, thermophilic
- D. Thermophilic, thermophobic, mesophobic
Correct Answer: C
Rationale: Rationale:
1. Psychrophilic: Grow best in cold temperatures
2. Mesophilic: Grow best in moderate temperatures
3. Thermophilic: Grow best in high temperatures
- Choice A is incorrect as "thermophobic" is not a recognized term.
- Choice B is incorrect as "psychophobic" is not a recognized term.
- Choice D is incorrect as "mesophobic" is not a recognized term.
Rheumatic fever is usually a complication of a(n) __________ infection.
- A. Escherichia coli
- B. Streptococcus pyogenes
- C. Staphylococcus epidermidis
- D. Staphylococcus aureus
Correct Answer: B
Rationale: Rationale:
1. Streptococcus pyogenes is the causative agent of strep throat.
2. If untreated, strep throat can lead to rheumatic fever.
3. Rheumatic fever is an autoimmune complication of streptococcal infections.
4. E. coli, S. epidermidis, and S. aureus are not typically associated with rheumatic fever.