Nursing Elites

1. Isotopes are variants of a single element that differ in:

• A. Having the same number of protons but varying numbers of neutrons
• B. Having the same number of neutrons but varying numbers of protons
• C. Having the same mass but different atomic numbers
• D. None of the above

Correct answer: A

Rationale: Isotopes are variants of a single element that have the same number of protons, the defining characteristic of an element. They differ in the number of neutrons they possess, leading to isotopes having different atomic masses while retaining the same chemical properties. Choice B is incorrect because isotopes have the same number of neutrons and differ in the number of protons. Choice C is incorrect because isotopes have different masses due to varying numbers of neutrons, not different atomic numbers. Choice D is incorrect as isotopes do differ in the number of neutrons they possess.

2. Which of the following correctly matches a category of protein with a physiological example?

• A. Keratin is a structural protein
• B. Antigens are hormonal proteins
• C. Channel proteins are marker proteins
• D. Actin is a transport protein

Correct answer: A

Rationale: Keratin is indeed a type of structural protein found in the skin, hair, and nails of animals. It provides strength and protection, helping to maintain the overall structure of these tissues. The other choices are incorrect as antigens are not hormonal proteins but rather are involved in immune response, channel proteins are involved in facilitating the transport of ions or molecules across cell membranes, and actin is primarily involved in cell structure and movement, not as a transport protein.

3. Molecular clocks utilize the accumulation of mutations in DNA sequences to estimate the evolutionary divergence time between species. This method relies on the assumption that:

• A. The rate of mutation is constant across all genes and all species.
• B. Species with more morphological similarities diverged more recently.
• C. Mutations are always beneficial and contribute to increased fitness.
• D. The fossil record provides the most accurate estimates of evolutionary relationships.

Correct answer: A

Rationale: A molecular clock is a method used to estimate the time of divergence between species by measuring the accumulation of mutations in DNA sequences. This method relies on the assumption that mutations occur at a relatively constant rate over time. If the rate of mutation were not constant, it would be challenging to accurately estimate the evolutionary divergence time between species. Therefore, option A is the most appropriate choice as it aligns with the fundamental principle underlying the molecular clock hypothesis. Option B is incorrect because the assumption that species with more morphological similarities diverged more recently does not directly relate to the concept of molecular clocks and the accumulation of mutations in DNA sequences. Option C is incorrect because mutations are not always beneficial and do not always contribute to increased fitness. Mutations can be neutral or deleterious as well, and their accumulation is what is used to estimate evolutionary di

4. What type of muscle is found in the walls of the heart?

• A. Smooth muscle
• B. Cardiac muscle
• C. Skeletal muscle
• D. Voluntary muscle

Correct answer: B

Rationale: The correct answer is B: Cardiac muscle. Cardiac muscle is the specialized muscle found in the walls of the heart. It contracts involuntarily to pump blood throughout the body, ensuring circulation. Smooth muscle is typically found in organs like the intestines and blood vessels, aiding in their functions. Skeletal muscle is attached to bones and plays a vital role in movement and posture. Voluntary muscle is a general term for skeletal muscles that are under conscious control, unlike cardiac muscle which contracts involuntarily to maintain the heart's continuous pumping action.

5. When human cells divide by meiosis, how many chromosomes do the resulting cells contain?

• A. 96
• B. 54
• C. 46
• D. 23

Correct answer: D

Rationale: When human cells divide by meiosis, the resulting cells contain 23 chromosomes. This is because meiosis is a cell division process that reduces the chromosome number by half, resulting in cells with a haploid number of chromosomes. In humans, the diploid number of chromosomes is 46. Therefore, after meiosis, the resulting cells have 23 chromosomes, ensuring the correct chromosome number is restored upon fertilization. Choices A, B, and C are incorrect as they do not represent the correct chromosome number resulting from meiosis in human cells.

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