Which of the following bacteria is known for causing urinary tract infections?

Correct Answer: A

Rationale: The correct answer is A: Escherichia coli. E. coli is the most common bacteria responsible for causing urinary tract infections due to its ability to adhere to the urinary tract lining and multiply rapidly. It is a normal inhabitant of the gut and can enter the urinary tract through improper hygiene practices. Salmonella enterica and Neisseria gonorrhoeae are typically associated with other infections like food poisoning and gonorrhea, respectively. Mycobacterium tuberculosis causes tuberculosis, not urinary tract infections. Thus, based on its prevalence and pathogenicity in the urinary tract, E. coli is the correct choice.

Correct Answer: C

Rationale: The correct answer is C: Carry genes for antibiotic resistance. Bacterial plasmids are small, circular DNA molecules that can be transferred between bacteria, carrying genes such as antibiotic resistance. This allows bacteria to survive in the presence of antibiotics. Plasmids do not directly play a role in protein synthesis (choice A) or DNA replication (choice B). Plasmids are not responsible for motility (choice D) as that function is usually carried out by flagella or other cellular structures.

Correct Answer: B

Rationale: The correct answer is B: Extracellular. Heparin works by inhibiting clotting factors in the blood outside of cells, preventing the formation of blood clots. It does not directly affect cellular, neuromuscular, or intracellular processes. By targeting extracellular factors, heparin effectively reduces the ability of blood to clot, making it an effective anticoagulant. The other choices are incorrect because heparin does not act on cellular, neuromuscular, or intracellular sites in the body to decrease blood clotting.

Correct Answer: C

Rationale: The bacterial capsule is composed of polysaccharides. This outer layer helps bacteria evade the host immune system, protect against desiccation, and aid in attachment to host cells. Polysaccharides are long chains of sugar molecules, providing a protective barrier for the bacteria. Lipopolysaccharides (choice A) are found in the outer membrane of Gram-negative bacteria and are not a major component of the capsule. Teichoic acid (choice B) is a component of the cell wall in Gram-positive bacteria, not the capsule. Peptidoglycan (choice D) is another component of the cell wall but is not part of the capsule.

Correct Answer: A

Rationale: The correct answer is A: proteins. Enzymes are mostly composed of proteins due to their complex structure and specific amino acid sequences that are essential for their catalytic activity. Proteins have active sites that bind to substrates and facilitate chemical reactions. Lipids (B), nucleic acids (C), and carbohydrates (D) do not possess the necessary properties and structures to function as enzymes. Lipids serve as energy storage molecules and cell membrane components, nucleic acids store genetic information, and carbohydrates are primarily used for energy production.

Correct Answer: A

Rationale: The correct answer is A: Epidemic typhus. This disease is caused by the bacterium Rickettsia prowazekii, which is transmitted by body lice. The symptoms include high fever, body rash, and tiny wounds due to scratching. The presence of lice in the clothing suggests a possible lice-borne disease like epidemic typhus. Summary: - B: Tularemia is caused by the bacterium Francisella tularensis, transmitted through ticks, deer flies, and contact with infected animals. Lice are not involved in its transmission. - C: Scabies is a skin infestation caused by the mite Sarcoptes scabiei, leading to itching and skin rashes. It is not associated with high fever or lice infestation. - D: Malaria is caused by Plasmodium parasites, transmitted by infected mosquitoes. The symptoms differ from those described in the scenario, and lice are not involved in its

Correct Answer: A

Rationale: The correct sequence of stages in the multiplication of animal viruses is as follows: 1. Adsorption: Virus attaches to host cell. 2. Penetration: Virus enters host cell. 3. Uncoating: Viral genetic material is released. 4. Replication: Viral genetic material replicates. 5. Assembly: New viral particles are assembled. 6. Release: New viral particles are released from the host cell. Choice A is correct as it follows the correct chronological order of virus multiplication stages. Choice B is incorrect as it has the wrong order of penetration and adsorption. Choice C is incorrect as it has the wrong order of adsorption, uncoating, and penetration. Choice D is incorrect as it has the wrong order of penetration and uncoating.

Correct Answer: A

Rationale: The correct answer is A: Cell wall. In the Gram staining method, the primary differentiation of bacteria is based on the composition of their cell walls. Gram-positive bacteria have a thick layer of peptidoglycan in their cell walls, which retains the crystal violet dye and appears purple under the microscope. On the other hand, Gram-negative bacteria have a thinner layer of peptidoglycan and an outer membrane, which allows the crystal violet dye to be washed out during the decolorization step and take up the counterstain safranin, appearing pink. The different responses to stains are primarily due to the structural differences in the cell walls of these two types of bacteria. Summary: - Choice A: Cell wall is correct because it determines the differential staining in Gram staining. - Choice B: Cytoplasm is incorrect as it does not directly influence the staining properties of bacteria. - Choice C: Cytoplasmic membrane is incorrect as it is not the main structural

Correct Answer: A

Rationale: The correct answer is A because differential growth media, such as Endo agar and MacConkey agar, contain specific indicators or substrates that allow for the differentiation of microorganisms based on their metabolic properties. For example, Eosin methylene blue agar differentiates between lactose fermenting and non-fermenting bacteria based on color changes. Levine's formulation is selective for Gram-negative bacteria due to bile salts and crystal violet. In contrast, the other choices do not have specific indicators for differentiation among microorganisms. Lowenstein-Jensen and SS agar are selective media for mycobacteria and Salmonella/Shigella species, respectively. ACA and BPLS agar are selective but not differential, and Nutrient agar and Peptone water are general-purpose media without differential properties.