Permeases are specific carriers involved in

Correct Answer: D

Rationale: The correct answer is D: active transport system. Permeases are specific carriers that actively transport molecules across a cell membrane against their concentration gradient, requiring energy input. This process is known as active transport, which is essential for maintaining cellular homeostasis and allowing the cell to accumulate specific molecules. Facilitated diffusion (A) and passive transport (B) both involve the movement of molecules down their concentration gradient without the need for energy input. Simple diffusion (C) also does not involve specific carriers and relies on the natural movement of molecules from areas of high concentration to low concentration. Therefore, the correct choice is D as permeases specifically function in active transport systems.

Correct Answer: A

Rationale: The correct answer is A: Clostridium tetani. The presence of Gram-positive rods with terminal spores resembling drumsticks indicates Clostridium tetani, the causative agent of tetanus. This bacterium forms spores at one end, giving it a drumstick appearance under the microscope. Clostridium perfringens (B) and Clostridium botulinum (D) do not have terminal spores. Bacillus anthracis (C) forms spores but typically appears as a square-ended or bamboo stick shape. Therefore, based on the microscopy findings, Clostridium tetani is the most likely microorganism responsible for the wound infection.

Correct Answer: D

Rationale: The correct answer is D: Granulomatosis. The appearance of a 10 mm papule 48 hours after the Mantoux test indicates a delayed-type hypersensitivity reaction, which is characteristic of granulomatosis. This type of reaction involves activation of macrophages and T cells, leading to the formation of granulomas. Granulomas are organized collections of immune cells that wall off the antigen, in this case, the tuberculin antigen. A, B, and C are incorrect: A: Cellular cytotoxicity involves the destruction of target cells by immune cells such as cytotoxic T cells or natural killer cells. This mechanism is not associated with the delayed-type hypersensitivity reaction seen in granulomatosis. B: Anaphylaxis is a rapid and severe allergic reaction involving IgE-mediated release of histamine and other inflammatory mediators. This is not the mechanism underlying the delayed-type hypersensitivity reaction in the Mantoux test. C: Antibody-dependent cytotoxic

Correct Answer: B

Rationale: The central dogma of molecular biology, which describes the flow of genetic information from DNA to RNA to proteins, was first proposed by Francis Crick. Crick, along with James Watson, discovered the structure of DNA in 1953, leading to the understanding of how genetic information is stored and transmitted. Ernst Ruska was a physicist who developed the electron microscope, not related to genetic information flow. Camillo Golgi was an Italian biologist known for the discovery of the Golgi apparatus, not central to the central dogma. Carl Bender is not a prominent figure in the field of molecular biology. In summary, Francis Crick is the correct answer as he played a pivotal role in introducing the central dogma of molecular biology.

Correct Answer: D

Rationale: The correct answer is D: mixed infection. In a mixed infection, multiple infectious agents establish themselves at the same site, leading to a complex and diverse infection. This type of infection can involve different types of pathogens such as bacteria, viruses, fungi, and parasites. It can be challenging to diagnose and treat due to the presence of multiple pathogens. A: Chronic infection refers to an infection that persists over a long period but is typically caused by a single pathogen. B: Necrotizing infection is characterized by rapid tissue destruction but does not necessarily involve multiple infectious agents. C: Fatal infection does not specify the presence of multiple infectious agents, it simply implies that the infection leads to death. In summary, the correct answer, mixed infection, is the only choice that specifically describes the scenario of multiple infectious agents establishing themselves at the same site.

Correct Answer: B

Rationale: The correct answer is B: Tuberculosis and mycobacterioses. Mycobacterium tuberculosis, the causative agent of tuberculosis, and other mycobacteria can survive in the soil for extended periods. Here's the rationale: 1. Mycobacteria have a waxy cell wall that provides resistance to harsh environmental conditions. 2. The slow growth rate of mycobacteria allows them to persist in the soil for long periods. 3. Tuberculosis and mycobacterioses are known to be transmitted through environmental exposure, including soil. 4. Colibacillosis and cholera (Choice C) are caused by enteric bacteria that do not survive well in soil. 5. Leptospirosis and plague (Choice D) are bacterial diseases transmitted through animal hosts and are not known to be soil-borne.

Correct Answer: A

Rationale: The correct answer is A: spleen. The spleen is not a component of the gastrointestinal tract; it is part of the lymphatic system. The pharynx, esophagus, and stomach are all part of the gastrointestinal tract responsible for digestion and absorption of food. The spleen's main functions include filtering blood, storing blood cells, and supporting the immune system, making it unrelated to the digestive process.

Correct Answer: A

Rationale: The correct answer is A: Streptococcus pneumoniae. This bacterium is the most likely causative agent because it is a Gram-positive cocci in pairs with a capsule, which matches the description provided. S. pneumoniae is a common cause of bacterial pharyngitis and can present with sore throat. Summary of other choices: B: Staphylococcus aureus is a Gram-positive cocci in clusters, not pairs, and is not typically associated with sore throat. C: Neisseria meningitidis is a Gram-negative diplococcus and more commonly causes meningitis or septicemia, not sore throat. D: Klebsiella pneumoniae is a Gram-negative rod bacterium, not a Gram-positive cocci, and is not a common cause of sore throat.

Correct Answer: A

Rationale: Step-by-step rationale: 1. Mycobacterium tuberculosis is the causative agent of tuberculosis. 2. Mycobacterium tuberculosis is a slow-growing, acid-fast bacterium. 3. It primarily infects the lungs and can spread to other parts of the body. 4. Bacillus anthracis causes anthrax, Clostridium tetani causes tetanus, and Treponema pallidum causes syphilis. 5. Therefore, choice A, Mycobacterium tuberculosis, is the correct answer for the bacteria responsible for tuberculosis.