Chlorine belongs to which of the following chemical groups?

Correct Answer: A

Rationale: The correct answer is A: Halogens. Chlorine belongs to the halogens group because it is a nonmetal element in group 17 of the periodic table. Halogens are highly reactive elements that have 7 electrons in their outer shell, making them eager to gain an electron to achieve stability. Chlorine specifically is a diatomic molecule with the chemical symbol Cl and atomic number 17. Option B: Heavy metals are elements with high atomic weights and densities, such as lead and mercury, which are not related to chlorine. Option C: Phenols are a class of organic compounds containing a hydroxyl group bonded to an aromatic ring, not related to chlorine. Option D: Alcohols are organic compounds characterized by the presence of a hydroxyl group (-OH), also not related to chlorine.

Correct Answer: B

Rationale: The correct answer is B. Bacilli are rod-shaped bacteria, some of which are endospore forming. Cocci are spherical, spirals are spiral-shaped, and vibrios are curved rod-shaped bacteria. Bacilli specifically refer to rod-shaped bacteria, making it the correct answer in this context.

Correct Answer: A

Rationale: The correct answer is A: nucleic acid and proteins. Viruses consist of genetic material (nucleic acid) surrounded by a protein coat. The nucleic acid carries the viral genetic information, while the proteins form the capsid that protects the genetic material. This combination is essential for the virus to infect host cells and replicate. Lipids (choice B) are not typically part of the main structure of viruses. Lipids are more commonly found in the host cell membrane. Lipids and proteins (choice C) may be present in the viral envelope but are not the main structural components. Proteins and glycoproteins (choice D) are important for viral attachment and entry into host cells but do not constitute the main structural components of viruses.

Correct Answer: C

Rationale: The correct answer is C because Rotaviruses are not a major cause of meningitis; they primarily cause gastroenteritis. This is because Rotaviruses infect the gastrointestinal tract, not the central nervous system. Choice A is incorrect because there is no specific antiviral therapy for Rotaviruses. Choice B is correct as Rotaviruses are indeed widespread globally. Choice D is correct as Rotaviruses are shed in large amounts in feces, contributing to their ability to spread easily.

Correct Answer: A

Rationale: The correct answer is A: Co-trimoxazole. This drug combination is the first-line treatment for toxoplasmosis due to its efficacy against Toxoplasma gondii. Co-trimoxazole consists of sulfamethoxazole and trimethoprim, which work synergistically to inhibit bacterial and protozoal folate synthesis, effectively treating toxoplasmosis. B: Itraconazole is an antifungal medication and not effective against toxoplasmosis. C: Mebendazole is an anthelmintic drug used for treating parasitic worm infections, not toxoplasmosis. D: Azidothimidine, also known as AZT, is used for treating HIV, not toxoplasmosis.

Correct Answer: B

Rationale: The correct answer is B: Trimethoprim. Trimethoprim is a folate antagonist that inhibits dihydrofolate reductase, an enzyme essential for folate metabolism in bacteria. This disrupts bacterial DNA synthesis, leading to bacteriostatic effects. Methyl Penicillin (A) is a beta-lactam antibiotic that interferes with bacterial cell wall synthesis. Vancomycin (C) inhibits cell wall synthesis by binding to D-Ala-D-Ala terminus of cell wall precursors. Gentamicin (D) inhibits bacterial protein synthesis by binding to the 30S subunit of the bacterial ribosome.

Correct Answer: B

Rationale: The correct answer is B: Inactivation. In this method, the sputum sample is processed with a solution of caustic soda, which helps to kill any contaminants present and preserve the tuberculosis bacillus for microscopic examination. This step is crucial in ensuring accurate detection of the bacillus. A: Homogenization involves breaking down the sample to make it uniform, but it does not necessarily involve using caustic soda for inactivation. C: Flotation is a method used to separate different components based on their density and is not specific to inactivating tuberculosis bacillus. D: Filtration involves passing a sample through a filter to separate particles based on size and is not related to inactivating the tuberculosis bacillus.

Correct Answer: A

Rationale: The correct answer is A: Tryptic soy agar is a general-purpose medium suitable for cultivating a wide range of microorganisms. It provides essential nutrients for growth without inhibiting specific types of bacteria. Blood agar (B), Mannitol salt agar (C), and MacConkey agar (D) are selective or differential media designed to promote the growth of specific types of bacteria or differentiate between different bacterial species. Therefore, they are not considered general-purpose mediums.

Correct Answer: C

Rationale: The correct answer is C: Obligate anaerobes cannot tolerate oxygen. They lack the enzymes needed to detoxify reactive oxygen species generated in the presence of oxygen. This makes them unable to survive in oxygen-rich environments. Choice A is incorrect because obligate anaerobes do not require oxygen to survive. Choice B is incorrect because obligate anaerobes specifically require the absence of oxygen. Choice D is incorrect because obligate anaerobes cannot even tolerate low levels of oxygen.