Which of the following complement proteins is not part of the membrane attack complex?
- A. C5a
- B. C5b
- C. C6
- D. C7
Correct Answer: A
Rationale: The correct answer is A: C5a. C5a is not part of the membrane attack complex (MAC). The MAC consists of C5b, C6, C7, C8, and multiple C9 molecules. C5a is a chemotactic factor that attracts immune cells to the site of infection, while C5b initiates the formation of the MAC. Choices B, C, and D (C5b, C6, C7) are all components of the MAC and play crucial roles in the formation and function of the complex.
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What is the medical term for an abnormal decrease in platelets?
- A. Leukopenia
- B. Thrombocytopenia
- C. Anemia
- D. Hemolysis
Correct Answer: B
Rationale: The correct answer is B: Thrombocytopenia, which refers to an abnormal decrease in platelets. Platelets are crucial for blood clotting. Leukopenia (A) is a decrease in white blood cells, not platelets. Anemia (C) is a decrease in red blood cells, not platelets. Hemolysis (D) is the breakdown of red blood cells, not related to platelet count. Therefore, B is the correct answer as it specifically addresses a decrease in platelet count, leading to potential bleeding issues.
Smack' is a drug obtained from the:
- A. latex of Papaver somniferum
- B. leaves of Cannabis sativa
- C. flowers of Dhatura
- D. fruits of Erythroxylum coca
Correct Answer: A
Rationale: The correct answer is A. Smack is a street name for heroin, which is derived from the latex of Papaver somniferum, commonly known as the opium poppy. The latex of this plant contains morphine and codeine, which are the main components of heroin. Cannabis sativa (B) refers to marijuana, not smack. Dhatura (C) and Erythroxylum coca (D) are sources of other drugs like scopolamine and cocaine, respectively, not heroin. Therefore, A is the correct answer as it corresponds to the actual source of smack/heroin.
Identify the following types of cells that do HIV preferentially infect.
- A. Memory cells
- B. Helper T cells
- C. Cytotoxic T cells
- D. Natural killer cells
Correct Answer: B
Rationale: The correct answer is B: Helper T cells. HIV preferentially infects Helper T cells because they express the CD4 receptor, which serves as the primary binding site for the virus. Once infected, HIV impairs the Helper T cells' function, leading to immune system dysfunction. Memory cells (A), Cytotoxic T cells (C), and Natural killer cells (D) are not the primary targets of HIV infection as they do not express the CD4 receptor necessary for HIV entry and replication. Helper T cells are crucial for orchestrating immune responses, making them the primary target for HIV infection.
Vibrations from the sound waves are amplified by
- A. the eardrum
- B. Anvi
- C. Stirrup
- D. All above
Correct Answer: D
Rationale: The correct answer is D: All above. The vibrations from sound waves are amplified by the eardrum, Anvil (also known as the Incus), and Stirrup (also known as the Stapes), which are the three tiny bones in the middle ear. The sound waves travel through the ear canal and hit the eardrum, causing it to vibrate. The vibration is then transmitted through the Anvil to the Stirrup, which amplifies the vibrations and sends them to the inner ear. Each of these three components plays a crucial role in the process of amplifying sound vibrations for better auditory perception. Therefore, all three choices are correct in this context.
Which of the following statement concerning Influenza infection is NOT true?
- A. There is evidence that the infection is less common in spring/summer because the transmission of bigger droplets formed at higher temperatures requires more close contact among people
- B. People infected with Flu can spread the disease before becoming symptomatic
- C. The human strains infect cells of the respiratory tract and also extensively infect epithelial cells throughout the body, explaining the systemic symptoms of influenza
- D. The virus hemagglutinin (HA) allows cell infection via the binding to sialic acid on carbohydrates expressed on host cells
Correct Answer: C
Rationale: The correct answer is C because it states that human strains of Influenza extensively infect epithelial cells throughout the body, which is not true. Influenza primarily infects cells of the respiratory tract, leading to respiratory symptoms. Systemic symptoms such as fever, fatigue, and muscle aches are more related to the body's immune response rather than widespread infection of epithelial cells throughout the body. This statement is incorrect as it misrepresents the pathogenesis of Influenza. Choices A, B, and D are incorrect because they are all true statements supported by scientific evidence regarding Influenza transmission, asymptomatic spread, and viral entry mechanism, respectively.