Cells that contain a nucleus are __________ cells.

Correct Answer: B

Rationale: The correct answer is B: eukaryotic. Eukaryotic cells have a well-defined nucleus that encloses the genetic material. The nucleus is a distinguishing feature of eukaryotic cells, separating them from prokaryotic cells (choice A) which lack a nucleus. Anucleate cells (choice C) are cells that do not have a nucleus at all. Haploid cells (choice D) contain a single set of chromosomes, but this does not necessarily imply the presence of a nucleus. Therefore, the presence of a nucleus is what categorizes cells as eukaryotic.

Correct Answer: B

Rationale: The correct answer is B: Capsule. Capsules are a protective layer outside the bacterial cell wall that helps bacteria evade phagocytosis by immune cells. The capsule inhibits phagocytic cells from engulfing the bacteria, making it difficult for them to be recognized and destroyed. A: Flagella - Flagella are not involved in protecting bacteria from phagocytosis. They are responsible for bacterial movement. C: Endospore - Endospores are dormant, resistant structures formed by some bacteria in response to harsh conditions. They do not directly protect against phagocytosis. D: Pili - Pili are hair-like structures used for adhesion and conjugation, not for protection against phagocytosis.

Correct Answer: A

Rationale: The correct answer is A: epidermis. Langerhans cells are a type of immune cell found in the epidermis, the outermost layer of the skin. They play a crucial role in the defense against microbes by capturing and presenting antigens to activate the immune system. The dermis (B), hypodermis (C), and subcutaneous layer (D) are located deeper in the skin and do not contain Langerhans cells. Therefore, the epidermis is the correct location for these immune cells to carry out their defensive functions.

Correct Answer: A

Rationale: The correct answer is A: yeast and molds. Yeast and molds can resist acidic pH due to their ability to maintain a stable internal pH through various mechanisms such as ion transport and cell wall composition. Bacteria, including E. coli, are generally more sensitive to acidic conditions. Choice D is incorrect as yeast and molds are known to thrive in acidic environments.

Correct Answer: C

Rationale: The correct staining technique for staining sputum smears from a tuberculosis patient is Ziehl-Neelsen staining. This technique uses a carbol fuchsin stain that specifically stains acid-fast organisms like Mycobacterium tuberculosis. The steps involved include staining with carbol fuchsin, decolorizing with acid-alcohol, counterstaining with methylene blue, and then examining under a microscope. This staining method is crucial for detecting the acid-fast bacilli characteristic of tuberculosis. Explanation for incorrect choices: A: Gram staining is used to differentiate bacteria into Gram-positive and Gram-negative, not suitable for acid-fast organisms like Mycobacterium tuberculosis. B: Giemsa staining is used for detecting parasites and certain types of white blood cells, not specific for acid-fast bacteria. D: Burry staining is not a recognized staining technique in microbiology for staining acid-fast organisms.

Correct Answer: D

Rationale: The correct answer is D because viruses are sensitive to interferon, a natural defense mechanism of the body against viral infections. Interferon helps to inhibit viral replication. A: Viruses are cell-free infectious particles, not living systems. B: Viruses are obligate intracellular parasites as they require host cells to replicate. C: Viruses can have either DNA or RNA as genetic material, which is a characteristic feature.

Correct Answer: B

Rationale: The correct answer is B: Pseudomonas aeruginosa. This bacterium is important for controlling air quality as it can degrade a wide range of organic compounds present in the air, helping to maintain a clean and healthy environment. Alpha and beta-hemolytic streptococci (Choice A) are not typically associated with air quality control. E. coli (Choice C) and Salmonella spp. (Choice D) are more commonly found in water and food sources, not air, making them incorrect choices for this question. Pseudomonas aeruginosa's ability to break down organic matter in the air makes it the most suitable option for maintaining sanitary air quality.

Correct Answer: A

Rationale: The correct answer is A: Toxoplasmosis. Toxoplasmosis is a parasitic infection caused by Toxoplasma gondii, which can be transmitted from mother to fetus during pregnancy, leading to congenital toxoplasmosis. This infection can result in stillbirth, multiple developmental defects, and intrauterine death. Leishmaniasis (B), Malaria (C), and Amebiasis (D) are caused by different parasites and do not typically lead to intrauterine death or developmental defects in the fetus.

Correct Answer: C

Rationale: The correct answer is C: green monkeys. The Marburg virus was first identified in 1967 in Marburg and Frankfurt, Germany, after outbreaks in lab workers exposed to infected African green monkeys. These monkeys were imported from Uganda. The virus is believed to be originally endemic in certain species of African bats and is transmitted to humans through contact with infected animals. Choice A, laboratory rats, is incorrect as the virus did not originate from rats. Choice B, birds, and Choice D, wild turkeys, are also incorrect as there is no evidence linking these animals to the transmission of the Marburg virus.