Nokea
Which molecule released by NK cells is responsible for inducing apoptosis?
- A. Perforin
- B. Granzyme
- C. Cytokines
- D. Antibodies
Correct Answer: B
Rationale: The correct answer is B: Granzyme. Granzyme is the molecule released by NK cells that induces apoptosis in target cells. It enters the target cell through perforin, which creates pores in the target cell membrane. Cytokines are signaling molecules released by various immune cells but do not directly induce apoptosis. Antibodies are produced by B cells and do not induce apoptosis. Perforin aids in the delivery of granzyme but is not responsible for inducing apoptosis itself. Therefore, Granzyme is the correct choice for inducing apoptosis by NK cells.
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What did Paul Ehrlich predict in immunology?
- A. Existence of antibodies and their ability to bind toxins
- B. Discovery of germ theory
- C. Smallpox eradication
- D. Development of vaccines
Correct Answer: A
Rationale: Paul Ehrlich predicted the existence of antibodies and their ability to bind toxins. He introduced the concept of the side-chain theory, proposing that cells have specific receptors (later known as antibodies) that can bind to toxins and neutralize them. This groundbreaking idea laid the foundation for modern immunology. Ehrlich's work was instrumental in understanding the immune response and paved the way for advancements in vaccine development and disease treatment.
Choice B (Discovery of germ theory) is incorrect because it was proposed by Louis Pasteur and Robert Koch, not Paul Ehrlich. Choice C (Smallpox eradication) is incorrect as Ehrlich did not predict smallpox eradication. Choice D (Development of vaccines) is incorrect because while Ehrlich's work contributed to vaccine development, his specific prediction was about antibodies and their toxin-binding ability, not vaccines in general.
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.
What stimulates aldosterone secretion from the adrenal cortex?
- A. Excessive water intake
- B. Increased serum osmolality
- C. Decreased serum potassium
- D. Decreased sodium and water
Correct Answer: D
Rationale: Aldosterone secretion is stimulated by decreased sodium and water levels (renin-angiotensin-aldosterone system activation) and low blood pressure.
The basic structure of an antibody molecule is
- A. One light chain and one heavy chain that are covalently linked and form one antigen binding site
- B. Two identical heavy chains and two identical light chains that are covalently linked and form two antigen binding sites
- C. Two identical heavy chains and two identical light chains covalently linked to form one antigen binding site
- D. Two identical light chains that form the antigen binding site and two identical heavy chains that mediate the effector functions of antibodies
Correct Answer: B
Rationale: Rationale for Answer B:
1. Antibody structure consists of two identical heavy chains and two identical light chains.
2. These chains are covalently linked to form the Y-shaped structure of an antibody.
3. Each chain contributes to the formation of antigen-binding sites.
4. Therefore, two identical heavy chains and two identical light chains form two antigen-binding sites.
Summary of Incorrect Choices:
A: Incorrect because it describes only one antigen-binding site formed by one light chain and one heavy chain.
C: Incorrect because it describes one antigen-binding site formed by two identical heavy chains and two identical light chains.
D: Incorrect because it incorrectly describes the roles of light and heavy chains in antibody structure.
Rolling circle replication refers to:
- A. DNA replication in every prokaryotic cell division
- B. DNA transfer during conjugation
- C. mitosis
- D. meiosis
Correct Answer: B
Rationale: Rolling circle replication is a mechanism commonly observed in DNA transfer during bacterial conjugation. The process involves the transfer of a single strand of DNA that acts as a template for the synthesis of a complementary strand in the recipient cell. This results in the formation of a circular DNA molecule in the recipient cell. This mechanism is distinct from the semiconservative replication seen in prokaryotic cell division (Choice A), the cell division process of mitosis (Choice C), and the reduction division of meiosis (Choice D). Rolling circle replication is specific to the transfer of genetic material between bacterial cells during conjugation, making Choice B the correct answer.