ATI RN
microbiology chapter 14 test bank Questions
Question 1 of 5
Some of the viruses have a cubic type of symmetry, which in the shape of
Correct Answer: D
Rationale: The correct answer is D: icosahedral structure. Icosahedral symmetry is common in viruses due to its efficient packing of genetic material. It consists of 20 equilateral triangular faces and 12 vertices. This symmetry allows viruses to have a stable structure and optimal capacity for encapsulating their genetic material.
A: Tetrahedral structure is incorrect as it consists of 4 faces and is not commonly found in viruses.
B: Hexahedral structure is incorrect as it consists of 6 faces and is not a common symmetry type in viruses.
C: Dodecahedral structure is incorrect as it consists of 12 faces and is not typically seen in viruses.
In summary, the icosahedral structure is the correct choice due to its stability, efficient packing, and common presence in viral structures compared to the other options.
Question 2 of 5
Which of the following statements for S. Aureus is FALSE
Correct Answer: A
Rationale: The correct answer is A because Staphylococcus aureus can develop resistance to penicillin over time due to the production of beta-lactamase enzymes. This resistance mechanism makes it no longer susceptible to penicillin. The other choices are correct:
B) S. aureus can produce beta hemolysis,
C) it produces various toxins like hemolysins, leucocidins, and enterotoxins, and
D) it shows a positive catalase reaction due to the presence of catalase enzyme that converts hydrogen peroxide to water and oxygen.
Question 3 of 5
A smear of a patient's sputum suspected for tuberculosis was prepared and stained. The smear showed red bacilli against a blue background. What staining method was used?
Correct Answer: A
Rationale: The correct answer is A: Ziehl-Neelsen staining method. This method is used to detect acid-fast bacteria like Mycobacterium tuberculosis.
Step-by-step rationale: 1. Acid-fast bacteria resist decolorization with acid-alcohol. 2. The red bacilli seen in the smear indicate acid-fast bacteria. 3. Ziehl-Neelsen stain uses carbol fuchsin to stain acid-fast bacteria red. 4. The blue background is likely the counterstain methylene blue. Incorrect choices: B: Gram stain is for categorizing bacteria into Gram-positive or Gram-negative, not specific for acid-fast bacteria. C: Giemsa stain is used for blood films and detecting parasites, not acid-fast bacteria. D: Neisser stain is not a standard microbiological staining method.
Question 4 of 5
Which of the following statements is accurate in explaining why gram-negative bacteria are generally more resistant to penicillin than gram-positive bacteria
Correct Answer: C
Rationale: The correct answer is C: gram-negative bacteria have an outer membrane that acts as an extra barrier. This outer membrane in gram-negative bacteria contains lipopolysaccharides and porins, which restrict the entry of antibiotics like penicillin. The outer membrane acts as an additional layer of protection, making it harder for penicillin to penetrate and reach its target, the peptidoglycan layer.
Choices A, B, and D do not directly address the specific mechanism of resistance seen in gram-negative bacteria.
Choice A focuses on transpeptidase enzyme quantity, which is not the primary reason for penicillin resistance.
Choice B refers to β-lactamase enzymes in the periplasmic space, which are actually enzymes that degrade penicillin and contribute to resistance, but this is not unique to gram-negative bacteria.
Choice D mentions a thicker cell wall, which is a characteristic of gram-positive bacteria, not gram-negative bacteria.
Question 5 of 5
What is a viral capsid?
Correct Answer: B
Rationale: The correct answer is B because a viral capsid is a protein coat that surrounds and protects the viral nucleic acid (DNA or RN
A). It helps in the attachment of the virus to host cells and protects the genetic material during transmission.
Choice A is incorrect because a viral capsid is composed of proteins, not an envelope.
Choice C is incorrect because not all viruses have an outer membrane.
Choice D is incorrect because a viral capsid is primarily made up of proteins, not lipids.