Infectious agents of various ultrastructures can be etiological agents of infectious diseases. Which of the groups named below HAS NO cellular structure, protein synthesizing, enzyme and energy systems?

Correct Answer: A

Rationale: The correct answer is A: Viruses. Viruses are acellular, meaning they lack cellular structure, protein synthesizing ability, enzymes, and energy systems. They are essentially genetic material (DNA or RNA) enclosed in a protein coat. Fungi (B), bacteria (C), and protozoa (D) are all cellular organisms with protein synthesizing, enzyme, and energy systems. Viruses rely on host cells to replicate and carry out metabolic functions, making them distinct from other groups.

Correct Answer: D

Rationale: The correct answer is D: rectum. Pinworms typically inhabit the rectum area in humans, where they lay their eggs. This is because the female pinworm migrates to the rectum at night to deposit her eggs near the anus. Other choices are incorrect because pinworms do not reside in the duodenum (A), ileum (B), or transverse colon (C) as their primary location is in the lower gastrointestinal tract near the anus.

Correct Answer: A

Rationale: The correct answer is A: Kitt-Tarozzi. This medium contains blood and hemin, which are essential nutrients for the growth of anaerobes. Blood provides a source of iron, while hemin stimulates the growth of anaerobes. This combination creates an environment conducive for the isolation and identification of anaerobic organisms. B: Endo and C: Roux are selective media primarily used for the isolation of gram-negative bacteria and not specifically designed for anaerobes. D: Sabouraud's is a medium used for the cultivation of fungi, not anaerobes. In summary, Kitt-Tarozzi is the correct choice due to its specific nutrient composition that supports the growth of anaerobes, unlike the other options which are not suitable for this purpose.

Correct Answer: A

Rationale: The correct answer is A: IgG. IgG is the most abundant class of immunoglobulins in the body, constituting about 75% of total immunoglobulins. IgG plays a crucial role in long-term immunity, neutralizing toxins, and enhancing phagocytosis. IgE is involved in allergic reactions, IgD is mainly found on B cells and functions as a receptor, and IgM is the first antibody produced in response to an infection but is less abundant compared to IgG. Therefore, IgG is the correct choice based on its abundance and diverse functions in the immune system.

Correct Answer: A

Rationale: The correct answer is A: Clostridium botulinum and Clostridium tetani. Both bacteria produce exotoxins that affect the nervous system. Clostridium botulinum produces botulinum toxin, causing botulism, leading to muscle paralysis. Clostridium tetani produces tetanospasmin, causing tetanus, leading to muscle stiffness and spasms. Choice B (Escherichia coli and Salmonella) are known for causing gastrointestinal infections, not specifically affecting the nervous system. Choice C (Bacillus anthracis and Listeria monocytogenes) produce toxins that primarily affect other body systems, not the nervous system. Choice D (Pseudomonas aeruginosa and Staphylococcus aureus) are associated with skin and respiratory infections, not neurological effects.

Correct Answer: D

Rationale: The correct answer is D because the catarrhal stage of whooping cough is characterized by mild respiratory symptoms such as mild coughing, sneezing, or a runny nose. During this stage, the cough may start to worsen but is not yet severe. A: Incorrect - Decrease in paroxysms of coughing is not seen in the catarrhal stage; it occurs later in the paroxysmal stage. B: Incorrect - Subsequent respiratory infection for many months after the onset of pertussis is not a characteristic of the catarrhal stage. C: Incorrect - Uncontrollable coughing followed by a high pitched 'whoop' sound is typical of the paroxysmal stage, not the catarrhal stage.

Correct Answer: C

Rationale: The correct answer is C: Corynebacterium diphtheriae. This bacterium causes diphtheria, a disease characterized by a pseudomembrane in the throat. This pseudomembrane is a result of the bacterial exotoxins causing inflammation and necrosis of the throat tissues. Clostridium tetani (A) causes tetanus, characterized by muscle stiffness, not a pseudomembrane in the throat. Bordetella pertussis (B) causes whooping cough, with symptoms of severe coughing fits but no pseudomembrane. Streptococcus pyogenes (D) causes strep throat, but does not produce a pseudomembrane.

Correct Answer: D

Rationale: The correct answer is D: simple diffusion. In simple diffusion, molecules move from an area of high concentration to low concentration without the need for energy input. Hydrostatic pressure is a form of passive transport that drives molecules to equalize concentration. Filtration (A) involves the movement of solutes through a membrane under pressure. Exocytosis (B) is the process by which cells release substances outside the cell using energy. Osmosis (C) is the movement of water molecules across a selectively permeable membrane. Therefore, simple diffusion is the most appropriate choice in this scenario.

Correct Answer: C

Rationale: The correct answer is C: IgA. IgA is the most prominent immunoglobulin class present in external secretions like saliva, tears, and mucus. It plays a crucial role in mucosal immunity by preventing pathogens from entering the body. IgG is mainly found in the blood and tissues, IgM is the first antibody produced in response to an infection, and IgE is involved in allergic reactions. IgA's presence in external secretions helps protect the body from infections at mucosal surfaces, making it the correct choice in this context.