Nursing Elites

1. Homologous structures are similar structures in different organisms that have a common evolutionary origin. An example is:

• A. Butterfly wings and bird wings (analogous structures with different origins)
• B. The arm of a human, the wing of a bat, and the flipper of a whale
• C. The eyes of an octopus and a human (convergent evolution with different origins)
• D. The stinger of a bee and the barb of a cactus (unrelated structures)

Correct answer: B

Rationale: Homologous structures are similar structures found in different organisms that share a common evolutionary origin. The arm of a human, the wing of a bat, and the flipper of a whale are all examples of homologous structures. Despite serving different functions, they share a common underlying structure due to their evolutionary relationship, evidencing a shared ancestry. These structures are modified over time to suit the specific needs of each species. Option A (Butterfly wings and bird wings) refers to analogous structures with different origins. Option C (The eyes of an octopus and a human) describes convergent evolution where traits evolve independently. Option D (The stinger of a bee and the barb of a cactus) are unrelated structures.

2. What enzyme plays a key role in breaking down carbohydrates in the small intestine?

• A. Pepsin
• B. Lipase
• C. Amylase
• D. Trypsin

Correct answer: C

Rationale: Amylase is the enzyme responsible for breaking down carbohydrates in the small intestine. It specifically targets starches and sugars, breaking them down into smaller molecules like maltose and glucose that can be absorbed by the body. Pepsin is an enzyme that breaks down proteins in the stomach, not the small intestine. Lipase is responsible for breaking down fats, not carbohydrates. Trypsin is an enzyme that breaks down proteins in the small intestine, not carbohydrates.

3. Which of the following is a common property of both acids and bases?

• A. React with metals to produce hydrogen gas
• B. Taste sour
• C. Turn blue litmus paper red
• D. Conduct electricity when dissolved in water

Correct answer: D

Rationale: The correct answer is D. Both acids and bases can conduct electricity when dissolved in water. Acids ionize in water to produce H+ ions, which can carry an electric current, while bases ionize to produce OH- ions, which also conduct electricity. The other options are not common properties of both acids and bases. Reacting with metals to produce hydrogen gas is characteristic of acids, tasting sour is a property of acids, and turning blue litmus paper red is a property of bases, not a common property shared by both.

4. Which of the following is the base that will bind with cytosine?

• A. Adenine
• B. Cytosine
• C. Guanine
• D. Thymine

Correct answer: A

Rationale: Adenine is the correct answer as it is the base that binds with cytosine through hydrogen bonding in DNA, forming the A-T base pair. Cytosine always pairs with guanine to form the G-C base pair. Thymine pairs with adenine in DNA, not with cytosine.

5. Where are most of the body's immune cells located?

• A. Blood
• B. Brain
• C. Skin
• D. Large intestine

Correct answer: A

Rationale: - The majority of the body's immune cells are located in the blood. Immune cells, such as white blood cells (leukocytes), circulate throughout the body via the bloodstream to detect and fight off infections and foreign invaders. - While immune cells are also present in other parts of the body like the lymph nodes, spleen, and bone marrow, the blood serves as a primary conduit for immune cells to travel to different tissues and organs to carry out their functions. - The brain (option B) is protected by the blood-brain barrier, which limits the entry of immune cells into the brain to prevent inflammation and damage. - The skin (option C) contains immune cells like Langerhans cells that help protect against pathogens, but the largest concentration of immune cells is found in the blood. - The large intestine (option D) also houses a significant amount of immune cells due to its role in interacting with the external environment through the gut-associated lymphoid tissue, but the primary location for most of the body's immune cells is the blood.

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