Nursing Elites

1. Which of the following enzymes unwinds the double-stranded DNA during replication?

• A. Helicase
• B. Ligase
• C. Nuclease
• D. Polymerase

Correct answer: A

Rationale: Helicase is the enzyme responsible for unwinding the double-stranded DNA during replication by breaking the hydrogen bonds between the base pairs. This process creates the replication fork where DNA polymerase can then synthesize new DNA strands. Ligase functions to join Okazaki fragments on the lagging strand, not unwind DNA. Nuclease is involved in DNA repair by removing damaged DNA segments. Polymerase is responsible for synthesizing new DNA strands based on the existing template strands, not for unwinding the DNA.

2. How do isotopes affect the atomic mass of an element?

• A. Isotopes have no effect on the atomic mass of an element.
• B. Isotopes cause the atomic mass of an element to vary slightly.
• C. Isotopes cause the atomic mass of an element to be exactly the same for all isotopes of that element.
• D. Isotopes cause the atomic mass of an element to vary greatly.

Correct answer: B

Rationale: Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons. Since the atomic mass of an element is the weighted average of the masses of its isotopes, the presence of isotopes causes the atomic mass of an element to vary slightly. This variation occurs because different isotopes have different masses due to their varying numbers of neutrons. The atomic mass is affected by the abundance of each isotope, leading to a slight fluctuation in the overall atomic mass of the element. Choice A is incorrect because isotopes do influence the atomic mass. Choice C is incorrect because isotopes have different masses, affecting the overall atomic mass. Choice D is incorrect as isotopes typically do not cause a significant variation in atomic mass, but rather a slight fluctuation.

3. Which of the following is NOT an element of the respiratory system?

• A. Ribs
• B. Trachea
• C. Diaphragm
• D. Alveoli

Correct answer: A

Rationale: The correct answer is A: Ribs. The ribs are part of the skeletal system, providing structure and protection to the thoracic cavity. The trachea, diaphragm, and alveoli are all essential components of the respiratory system. The trachea carries air to and from the lungs, the diaphragm aids in breathing by contracting and relaxing to change the volume of the thoracic cavity, and the alveoli are tiny air sacs where gas exchange occurs in the lungs. Therefore, ribs do not play a direct role in the respiratory process and are not considered a part of the respiratory system.

4. Which of the following correctly lists the normal blood flow through the heart?

• A. Left ventricle, left atrium, body, right ventricle, right atrium, lungs
• B. Left atrium, left ventricle, lungs, right atrium, right ventricle, body
• C. Right atrium, right ventricle, lungs, left atrium, left ventricle, body
• D. Right ventricle, right atrium, body, left atrium, left ventricle, lungs

Correct answer: B

Rationale: The correct order of normal blood flow through the heart is as follows: from the body, blood flows into the right atrium, then to the right ventricle, followed by the lungs through the pulmonary artery for oxygenation. Oxygenated blood then returns to the heart through the pulmonary veins into the left atrium, then moves into the left ventricle before being pumped out to the body. Choice B correctly depicts this sequential flow of blood through the heart. Choices A, C, and D are incorrect as they do not follow the typical path of blood flow through the heart.

5. Which of the following is NOT a common route of transmission for a sexually transmitted infection (STI)?

• A. Unprotected sexual contact
• B. Sharing contaminated needles
• C. Deep kissing
• D. Mother to child during childbirth

Correct answer: C

Rationale: A) Unprotected sexual contact is a common route of transmission for sexually transmitted infections (STIs) as many STIs are spread through genital, anal, or oral sex without the use of barrier protection such as condoms. B) Sharing contaminated needles can also transmit STIs such as HIV and hepatitis B and C, especially among individuals who inject drugs. C) Deep kissing, while it can transmit certain infections like herpes simplex virus (HSV-1) or cytomegalovirus (CMV), is not a common route of transmission for most STIs. Although some STIs can be transmitted through saliva, deep kissing is not a primary mode of transmission for most STIs. D) Mother to child transmission during childbirth can occur with certain STIs such as HIV, syphilis, and herpes, where the infection can be passed from the mother to the baby during delivery. Therefore, deep kissing (option C) is the correct answer as it is not a typical route of transmission for most STIs.

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