Nursing Elites

1. Which valve prevents blood from entering the left atrium when the ventricles contract?

• A. Pulmonary valve
• B. Tricuspid valve
• C. Mitral valve
• D. Aortic valve

Correct answer: C

Rationale: The correct answer is the mitral valve, also known as the bicuspid valve. The mitral valve prevents blood from flowing back into the left atrium during ventricular contraction. The tricuspid valve is located between the right atrium and right ventricle, the pulmonary valve is between the right ventricle and the pulmonary artery, and the aortic valve is situated between the left ventricle and the aorta. Therefore, choices A, B, and D are incorrect as they are not related to preventing blood from entering the left atrium during ventricular contraction.

2. What property of a substance refers to its ability to be drawn into thin wires without breaking?

• A. Malleability
• B. Viscosity
• C. Ductility
• D. Conductivity

Correct answer: C

Rationale: Ductility is the property that allows a substance to be drawn into thin wires without breaking. Malleability, on the other hand, is the ability to be hammered or rolled into thin sheets. Viscosity is the measure of a fluid's resistance to flow. Conductivity, lastly, refers to a substance's ability to conduct electricity or heat. Therefore, in this context, the correct answer is ductility as it specifically relates to the ability of a substance to be drawn into thin wires without breaking.

3. How do vaccines stimulate the immune system to develop memory without causing full-blown illness? What type of molecule in a vaccine typically triggers the immune response?

• A. Toxins produced by the pathogen
• B. Live, attenuated (weakened) forms of the pathogen
• C. Inactivated (dead) forms of the pathogen
• D. Antigens (specific molecules) from the pathogen

Correct answer: D

Rationale: Vaccines work by triggering the immune system to develop memory without causing illness. They typically contain antigens, which are specific molecules from the pathogen. These antigens stimulate the immune system to produce a targeted immune response without causing full-blown sickness. By presenting these antigens, vaccines help the immune system create memory cells that remember the pathogen. This memory allows the immune system to respond more effectively if it encounters the pathogen in the future. Choices A, B, and C are incorrect because vaccines do not typically contain toxins, live pathogens, or inactivated forms of the pathogen. Instead, vaccines primarily rely on specific molecules (antigens) to induce an immune response.

4. What is hydroxyapatite?

• A. A mixture of minerals such as calcium and phosphorus that strengthen the collagen matrix of bone.
• B. The structural unit of a bone that runs the length of the bone.
• C. The covering of bones at the point of articulation to prevent grinding.
• D. The lightest portion of a long bone and concentrated at the ends.

Correct answer: A

Rationale: Hydroxyapatite is a mineral compound composed of calcium and phosphorus that plays a crucial role in strengthening the collagen matrix of bones, contributing to their structural integrity and hardness. It is a key component of bone tissue and provides the mineralization necessary for bone strength and density. Choice B is incorrect because the structural unit of a bone is the osteon or Haversian system, not hydroxyapatite. Choice C is incorrect as it describes cartilage, not hydroxyapatite. Choice D is incorrect as it refers to the epiphysis, which is not synonymous with hydroxyapatite.

5. Which of the following components is found in DNA?

• A. Uracil
• B. Deoxyribose
• C. Guanine
• D. Phosphate group

Correct answer: B

Rationale: The correct answer is B: Deoxyribose. DNA is composed of nucleotides containing deoxyribose sugar, phosphate group, and nitrogenous bases (adenine, thymine, guanine, and cytosine). Deoxyribose is the sugar component specific to DNA, while ribose is found in RNA. Guanine (choice C) is a nitrogenous base present in both DNA and RNA. Uracil (choice A) is a nitrogenous base specific to RNA, replacing thymine found in DNA. The phosphate group (choice D) is an essential part of nucleotides in both DNA and RNA, providing the backbone structure for the nucleic acid chains.

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