Nokea
Which scientist is credited with introducing the germ theory of disease?
- A. Louis Pasteur
- B. Edward Jenner
- C. Elie Metchnikoff
- D. Paul Ehrlich
Correct Answer: A
Rationale: Louis Pasteur is credited with introducing the germ theory of disease. He conducted experiments that demonstrated the role of microorganisms in causing infections. He also developed pasteurization to kill harmful bacteria in food and beverages. Edward Jenner is known for developing the smallpox vaccine, not the germ theory. Elie Metchnikoff studied the immune system and phagocytosis. Paul Ehrlich is known for his work on chemotherapy and the concept of the "magic bullet," targeting specific pathogens.
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What is the function of CD14 with respect to LPS recognition?
- A. It is an accessory protein that allows the transport of newly synthesized TLR-4 onto the cell membrane
- B. It is a cytosolic protein that binds LPS that has been internalized via TLR-4/MD-2
- C. It acts as an adaptor in the TLR-4 signaling pathway
- D. It is expressed on the cell membrane and shuttles LPS to the vicinity of TLR-4/MD-2
Correct Answer: D
Rationale: The correct answer is D because CD14 is a glycosylphosphatidylinositol (GPI)-anchored protein expressed on the cell membrane that binds to LPS and facilitates its delivery to the TLR-4/MD-2 complex for recognition. CD14 does not transport TLR-4 (Choice A), bind LPS internally (Choice B), or act as an adaptor in the signaling pathway (Choice C). The key role of CD14 is to shuttle LPS to TLR-4/MD-2, initiating the immune response.
Which complement protein is the main component of the Membrane Attack Complex (MAC)?
- A. C1
- B. C3
- C. C5b
- D. C4b
Correct Answer: C
Rationale: The correct answer is C: C5b. The Membrane Attack Complex (MAC) is formed by a sequence of complement proteins, with C5b playing a crucial role as the initiator. After C5b binds to the target cell membrane, it triggers the assembly of C6, C7, C8, and multiple C9 molecules to form the MAC pore. C1 (A) is the initiator of the classical pathway, not a component of the MAC. C3 (B) is involved in the formation of the C3 convertase and opsonization but is not the main component of the MAC. C4b (D) is part of the classical pathway and is involved in the formation of the C3 convertase, not the MAC.
What does the mechanism of chemotaxis accomplish?
- A. Causes the transformation of monocytes into macrophages
- B. Involves a pathway of chemical processes resulting in cellular lysis
- C. Attracts the accumulation of neutrophils and monocytes to an area of injury
- D. Slows the blood flow in a damaged area, allowing migration of leukocytes into tissue
Correct Answer: C
Rationale: Chemotaxis is the process by which immune cells such as neutrophils and monocytes are attracted to the site of injury or infection through chemical signals. These signals guide the cells to areas where they are needed most.
EcoRI restriction endonuclease reactions produce fragments with
- A. 3' cohesive ends
- B. blunt ends
- C. 5' cohesive ends
- D. none of the options are correct
Correct Answer: C
Rationale: EcoRI recognizes the palindromic sequence GAATTC and cuts between G and A on both strands, producing 5' cohesive ends. Cohesive ends can base-pair with complementary ends, facilitating DNA ligation. Blunt ends (choice B) are produced by enzymes that cut both DNA strands at the same position. Choice A is incorrect as EcoRI produces 5' cohesive ends, not 3' cohesive ends. Choice D is incorrect as EcoRI does produce cohesive ends.
Match the following:
- A. 1-c, 2-d, 3-b, 4-a
- B. 1-b, 2-d, 3-c, 4-a
- C. 1-b, 2-d, 3-a, 4-c
- D. 1-d, 2-c, 3-a, 4-b
Correct Answer: C
Rationale: The correct answer is C: 1-b, 2-d, 3-a, 4-c.
1. The first match should be b, as it aligns with the order given.
2. The second match should be d, as it aligns with the order given.
3. The third match should be a, as it aligns with the order given.
4. The fourth match should be c, as it aligns with the order given.
Therefore, option C is the correct match based on the given order. Other choices are incorrect because they do not align with the given order of matches.