The lipopolysaccharides of gram negative bacteria consists of all the following types except:

Correct Answer: D

Rationale: The correct answer is D: Protoplast. Lipopolysaccharides of Gram-negative bacteria consist of three main components: O-specific polysaccharide chain, R-specific polysaccharide chain, and Lipid A. Protoplast is not a component of lipopolysaccharides. O-specific polysaccharide chain is responsible for serotype specificity, R-specific polysaccharide chain varies among strains, and Lipid A is the endotoxin component. Protoplast refers to a bacterial cell devoid of a cell wall, which is not a component of lipopolysaccharides.

Correct Answer: A

Rationale: The correct answer is A: Icosahedral structures. Icosahedral symmetry is commonly found in viruses due to its efficient way of packing genetic material. The icosahedron has 20 equilateral triangular faces, making it ideal for viral capsids. The other choices, B: Hexahedral, C: Tetrahedral, and D: Dodecahedral structures, do not accurately describe the cubic type of symmetry seen in viruses. Hexahedral refers to a six-faced polyhedron, tetrahedral to a four-faced polyhedron, and dodecahedral to a twelve-faced polyhedron, none of which align with the structure commonly observed in viruses.

Correct Answer: D

Rationale: The correct answer is D because fungi do not form flagella. Fungi reproduce sexually and asexually (A) through spores, have a cell wall (B) made of chitin, and are mostly aerobic or facultative anaerobes (C). Flagella are structures found in some protozoa and bacteria, not in fungi. Therefore, option D is the only statement that is not true about fungi.

Correct Answer: A

Rationale: The correct answer is A: Trichomonas vaginalis. Trichomonas vaginalis is a sexually transmitted protozoan that causes trichomoniasis. The pear-shaped flagellated protozoa with an undulating membrane described in the question match the morphology of Trichomonas vaginalis. It is typically found in vaginal discharge of infected individuals. Giardia lamblia (B) is a different protozoan that causes giardiasis and has a distinct morphology of a teardrop shape with flagella. Trypanosoma brucei (C) causes African sleeping sickness and Leishmania donovani (D) causes visceral leishmaniasis, both of which have different morphologies and clinical presentations compared to Trichomonas vaginalis.

Correct Answer: D

Rationale: The correct answer is D: tinea pedis. Athlete's foot is a fungal infection that affects the feet, specifically the skin between the toes and on the soles. "Tinea pedis" is the medical term for athlete's foot, with "tinea" meaning a fungal infection and "pedis" referring to the foot. A: tinea capitis refers to a fungal infection of the scalp, not the feet. B: tinea corporis refers to a fungal infection of the body, not specifically the feet. C: tinea versicolor refers to a fungal infection that causes discoloration of the skin, not typically on the feet. In summary, the other choices are incorrect because they refer to fungal infections affecting different parts of the body, whereas "tinea pedis" specifically refers to athlete's foot.

Correct Answer: B

Rationale: The correct answer is B: focal. When a pathogen spreads from the original site to other tissues or organs, it is considered a focal infection. This term specifically refers to an infection that is localized to a specific area but can spread to other parts of the body. A: Local infection refers to an infection that is confined to a specific area without spreading to other tissues or organs. C: Natural is not a term commonly used to describe the spread of pathogens within the body. D: Acute refers to the rapid onset of a disease but does not specifically address the spread of pathogens from one site to another. In summary, the term "focal" best describes the scenario provided in the question, making it the correct answer.

Correct Answer: B

Rationale: The correct answer is B: autoclaving. Autoclaving is a process that uses high pressure and steam to achieve temperatures above the boiling point of water, typically around 121-134°C. This high heat and pressure are effective in destroying spore forms of microorganisms, which are highly resistant structures that can withstand boiling temperatures. Autoclaving ensures the complete destruction of spores, making it an effective method for sterilization. Rationale: A: Pasteurization uses lower heat compared to autoclaving and is not sufficient to destroy spore forms. C: Freezing does not effectively destroy spore forms, as most microorganisms can survive freezing temperatures. D: Boiling, while effective for many microorganisms, may not be sufficient to destroy spore forms due to their high resistance, unlike autoclaving.

Correct Answer: C

Rationale: The correct answer is C: tapeworms. Taeniasis is specifically caused by tapeworms of the Taenia species, such as Taenia solium. These parasitic worms infect the intestines of humans through consumption of contaminated food or water. Ringworms (choice A), hookworms (choice B), and pinworms (choice D) are all different types of parasites that cause distinct infections in the body, not taeniasis. Tapeworms are the only organisms among the choices that are directly associated with taeniasis due to their unique life cycle and mode of infection.

Correct Answer: B

Rationale: The correct answer is B because humoral immunity involves the formation of specific antibodies by B cells. B cells differentiate into plasma cells that produce antibodies to target specific antigens. T cells are involved in cell-mediated immunity, not humoral immunity. Choice A is incorrect because T cells do not produce antibodies. Choice C is incorrect as only B cells are responsible for antibody production in humoral immunity. Choice D is incorrect as B cells play a crucial role in the humoral immune response.