Nursing Elites

1. Which of the following is an example of a decomposition reaction?

• A. 2H2 + O2 → 2H2O
• B. CaCO3 → CaO + CO2
• C. 2Na + Cl2 → 2NaCl
• D. N2 + 3H2 → 2NH3

Correct answer: B

Rationale: A decomposition reaction involves a single compound breaking down into two or more simpler substances. In option B, CaCO3 breaks down into CaO and CO2, making it an example of a decomposition reaction. Options A, C, and D involve different types of chemical reactions such as synthesis, combination, and combustion, respectively. Option A represents a synthesis reaction, where two elements combine to form a compound. Option C demonstrates a combination reaction, where two elements combine to form a compound. Option D is an example of a synthesis reaction, where two reactants combine to form a single compound. It is important to recognize the specific characteristics of each type of chemical reaction to identify the correct example of decomposition reaction, where a compound breaks down into simpler products.

2. Which of the following antibodies can cross the placenta?

• A. IgA
• B. IgD
• C. IgG
• D. IgM

Correct answer: C

Rationale: The correct answer is IgG. IgG is the only antibody that can cross the placenta, providing passive immunity to the developing fetus. IgA, IgD, and IgM do not cross the placenta. IgA is mainly found in mucosal secretions, IgD is involved in the activation of B cells, and IgM is the first antibody produced in response to an infection, but it does not cross the placental barrier.

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 the feedback mechanism in the endocrine system that helps maintain hormone balance?

• A. Positive feedback, where a hormone stimulates its own release
• B. Negative feedback, where a hormone suppresses its own release
• C. Cascade effect, where one hormone triggers the release of another
• D. Dual hormone system, where two hormones work together

Correct answer: B

Rationale: In the endocrine system, negative feedback is the mechanism by which hormone levels are regulated. When hormone levels reach a certain threshold, they signal the body to stop producing more of that hormone, thus maintaining a balance. Negative feedback (option B) is the correct answer as it helps in preventing overproduction of hormones by suppressing their own release. Positive feedback (option A) would lead to an excessive production of hormones, disrupting the balance. The cascade effect (option C) involves one hormone triggering the release of another but does not directly regulate hormone levels. The dual hormone system (option D) refers to two hormones working together but does not specifically address the feedback mechanism for maintaining hormone balance.

5. 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.

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