Nokea
How does RNA polymerase differ from DNA polymerase?
- A. Both enzymes are identical in function and structure.
- B. RNA polymerase does not require a primer to initiate RNA synthesis.
- C. RNA polymerase can synthesize both RNA and DNA.
- D. RNA polymerase can only synthesize RNA, unlike DNA polymerase.
Correct Answer: B
Rationale: Rationale:
A) This statement is incorrect. RNA polymerase and DNA polymerase are not identical in function and structure. They have different roles in the cell.
B) This statement is correct. Unlike DNA polymerase, RNA polymerase does not require a primer to initiate RNA synthesis. RNA polymerase can start the synthesis of RNA de novo.
C) This statement is incorrect. RNA polymerase is specialized for synthesizing RNA, not DNA. DNA polymerase is responsible for synthesizing DNA.
D) This statement is correct. RNA polymerase can only synthesize RNA, while DNA polymerase is responsible for synthesizing DNA.
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Which of the following is an example of a chemical property of matter?
- A. Boiling point
- B. Flammability
- C. Density
- D. Conductivity
Correct Answer: B
Rationale: Flammability is an example of a chemical property of matter because it describes how a substance reacts with oxygen in the air to produce heat and light. Chemical properties involve the ability of a substance to undergo a chemical change or reaction, such as burning. Boiling point, density, and conductivity are examples of physical properties, not chemical properties. Boiling point is the temperature at which a substance changes from a liquid to a gas, density is the mass of a substance per unit volume, and conductivity is the ability to conduct electricity. Therefore, flammability best exemplifies a chemical property as it pertains to the substance's reaction with oxygen, while the other options are physical properties that describe characteristics without changing the substance's chemical composition.
What is the name of the growth plates in children's bones where new bone tissue is formed?
- A. Epiphyses
- B. Diaphysis
- C. Periosteum
- D. Medullary cavity
Correct Answer: A
Rationale: The correct answer is A: Epiphyses. Epiphyses are cartilaginous areas found at the ends of long bones, enabling growth and bone lengthening during childhood and adolescence. The diaphysis refers to the main shaft of a long bone. The periosteum is the outer bone layer responsible for nourishment and aiding in bone repair. The medullary cavity is the central cavity within the diaphysis that contains bone marrow but is not involved in new bone tissue formation.
Which of the following is the main organ responsible for producing antibodies?
- A. Thymus gland
- B. Spleen
- C. Bone marrow
- D. Lymph nodes
Correct Answer: C
Rationale: Antibodies are proteins produced by specialized white blood cells called B lymphocytes (B cells). These B cells mature in the bone marrow, where they undergo a process of differentiation and maturation to become plasma cells that secrete antibodies. The bone marrow is the primary site for the production of B cells and antibodies in the immune system. The thymus gland is responsible for the maturation of T lymphocytes (T cells), not antibody production. The spleen and lymph nodes play roles in filtering and trapping pathogens but are not the main organs responsible for producing antibodies.
What is the primary purpose of control rods within a nuclear reactor?
- A. Reflecting neutrons back into the core
- B. Absorbing excess neutrons to control criticality
- C. Moderating the velocity of neutrons
- D. All of the above
Correct Answer: B
Rationale: The primary purpose of control rods in a nuclear reactor is to absorb excess neutrons to control criticality. When inserted into the reactor core, control rods absorb neutrons, reducing the number available for sustaining the fission chain reaction. This action allows operators to manage the reactor power levels and prevent overheating or runaway reactions. Reflecting neutrons back into the core and moderating neutron velocity are not the primary functions of control rods in a nuclear reactor. Choice A is incorrect because control rods do not reflect neutrons back into the core but absorb them. Choice C is incorrect as the moderation of neutron velocity is typically achieved by other materials like a moderator (e.g., water, graphite) rather than control rods. Choice D is incorrect as control rods do not reflect neutrons or moderate neutron velocity, making it an incorrect option.
Which hormone stimulates the release of calcium from bones and increases blood calcium levels?
- A. Parathyroid hormone (PTH)
- B. Calcitonin
- C. Growth hormone
- D. Testosterone
Correct Answer: A
Rationale: Parathyroid hormone (PTH) is the correct answer. PTH stimulates the release of calcium from bones, leading to increased blood calcium levels. It acts on the bones to release calcium into the bloodstream, facilitates the kidneys' reabsorption of calcium, and triggers vitamin D activation to boost calcium absorption from the intestines.
Choice B, Calcitonin, is incorrect as it works in opposition to PTH by decreasing blood calcium levels through inhibiting calcium release from bones. Choices C and D, Growth hormone and Testosterone, are not directly involved in calcium homeostasis and do not regulate blood calcium levels through bone calcium release mechanisms.