Nursing Elites

1. Which enzyme plays a crucial role in DNA replication during the S phase of interphase?

• A. Helicase
• B. DNA polymerase
• C. Ligase
• D. Topoisomerase

Correct answer: B

Rationale: During the S phase of interphase, DNA replication takes place. DNA polymerase is the enzyme responsible for synthesizing new DNA strands by adding nucleotides in a complementary manner to the template strand. It plays a pivotal role in accurately replicating the entire genome. While helicase unwinds the double-stranded DNA for replication, topoisomerase relieves the tension in the DNA strands, and ligase joins the Okazaki fragments on the lagging strand. However, DNA polymerase directly participates in the synthesis of new DNA strands during replication, making it the correct answer.

2. What type of bond is present in salt?

• A. Ionic
• B. Nonpolar covalent
• C. Polar covalent
• D. Peptide

Correct answer: A

Rationale: The correct answer is 'Ionic.' Ionic bonds are formed in salts through the transfer of electrons between atoms, leading to the attraction between positively and negatively charged ions. This results in a stable ionic compound, such as common table salt (sodium chloride). Nonpolar covalent, polar covalent, and peptide bonds are not typically found in salts. Nonpolar covalent bonds involve the equal sharing of electrons, polar covalent bonds involve unequal sharing of electrons, and peptide bonds are specific to proteins, not salts.

3. Elements tend to gain or lose electrons to achieve stable electron configurations like those of noble gases. Their group number often indicates the number of electrons gained/lost and the resulting ionic charge, providing a good starting point for prediction.

• A. Ionic bonds involve electron sharing, while metallic bonds involve electron transfer.
• B. Ionic bonds are weak and directional, while metallic bonds are strong and non-directional.
• C. Ionic bonds exist between metals and non-metals, while metallic bonds exist only between metals.
• D. Ionic bonds form discrete molecules, while metallic bonds form extended structures.

Correct answer: C

Rationale: Ionic bonds typically form between metals and non-metals, where one atom donates electrons (cation) and the other accepts electrons (anion). This results in the transfer of electrons. Metallic bonds, on the other hand, occur between metal atoms where electrons are shared among a sea of delocalized electrons, leading to the characteristic properties of metals like malleability and conductivity. Choice A is incorrect because ionic bonds involve electron transfer, not sharing. Choice B is incorrect as ionic bonds are strong, not weak, and are non-directional, while metallic bonds are strong and non-directional. Choice D is incorrect as ionic bonds do not form discrete molecules but rather a lattice structure, whereas metallic bonds form extended structures.

4. What principle explains the relationship between pressure, volume, and temperature for ideal gases?

• A. Law of conservation of energy
• B. Newton's laws of motion
• C. Ideal gas law
• D. Archimedes' principle

Correct answer: C

Rationale: The correct answer is the Ideal Gas Law (Choice C). The ideal gas law, PV = nRT, describes the relationship between pressure (P), volume (V), temperature (T), and the number of moles of gas (n) for an ideal gas. It states that the product of pressure and volume is directly proportional to the absolute temperature of the gas when the number of moles is held constant. This law is a fundamental principle in understanding the behavior of ideal gases. Choices A, B, and D are incorrect. The Law of conservation of energy (Choice A) pertains to the principle that energy cannot be created or destroyed; Newton's laws of motion (Choice B) describe the relationship between the motion of an object and the forces acting on it; Archimedes' principle (Choice D) deals with the buoyant force exerted on an object immersed in a fluid. These principles are not directly related to the relationship between pressure, volume, and temperature for ideal gases.

5. From which type of tissue is the myelin sheath derived, a fatty substance that insulates nerve fibers?

• A. Epithelial tissue
• B. Muscle tissue
• C. Nervous tissue (glial cells)
• D. Connective tissue

Correct answer: C

Rationale: The myelin sheath, a fatty substance that insulates nerve fibers, is derived from nervous tissue, specifically glial cells. Glial cells, including oligodendrocytes in the central nervous system and Schwann cells in the peripheral nervous system, are responsible for producing the myelin sheath that surrounds and insulates nerve fibers, aiding in the conduction of nerve impulses. Epithelial tissue (Choice A), Muscle tissue (Choice B), and Connective tissue (Choice D) are not responsible for producing the myelin sheath; instead, nervous tissue (glial cells) plays this crucial role.

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