Nursing Elites

1. Enzymes are typically _ _.

• A. Fats
• B. Proteins
• C. Sugars
• D. Neurons

Correct answer: B

Rationale: Enzymes are typically proteins that act as biological catalysts, speeding up chemical reactions in living organisms. While most enzymes are made of proteins, a few exceptions, known as ribozymes, are made of RNA. Proteins are composed of amino acids arranged in specific sequences that give enzymes their unique shape and functionality. Choice A, 'Fats,' is incorrect as enzymes are not typically composed of fats. Choice C, 'Sugars,' is incorrect as enzymes are not typically composed of sugars. Choice D, 'Neurons,' is incorrect as neurons are a type of cell in the nervous system, not typically associated with enzymes.

2. Tonicity refers to the movement of:

• A. Water
• B. Solute
• C. Cells
• D. None of the above

Correct answer: A

Rationale: Tonicity refers to the movement of water across a membrane in response to differences in solute concentration. In a hypertonic solution, where there is a higher concentration of solutes outside the cell, water will move out of the cell to try to reach equilibrium. In a hypotonic solution, where there is a lower concentration of solutes outside the cell, water will move into the cell to balance the concentrations. Cells and solutes themselves do not actively move in response to tonicity; it is the movement of water that helps achieve equilibrium. Therefore, the correct answer is water (Choice A). Choices B, C, and D are incorrect as tonicity specifically refers to water movement and not the movement of solutes, cells, or none of the above.

3. Why is DNA important for metabolic activities of the cell?

• A. It controls the synthesis of enzymes.
• B. It stabilizes the cell wall.
• C. It initiates cell division.
• D. It prevents diffusion of nutrients.

Correct answer: A

Rationale: The correct answer is A. DNA plays a crucial role in metabolic activities by controlling the synthesis of enzymes. Enzymes are the biological catalysts that regulate and facilitate metabolic reactions within the cell. Choice B is incorrect because DNA is not involved in stabilizing the cell wall; that role is usually associated with other components like the cell membrane. Choice C is incorrect as cell division is primarily regulated by different processes and molecules, not directly by DNA. Choice D is incorrect because DNA is not related to preventing the diffusion of nutrients; instead, it is involved in coding for proteins that aid in various cellular functions.

4. Which one of the following best describes the function of a cell membrane?

• A. It controls the substances entering and leaving the cell.
• B. It maintains the cell's shape.
• C. It controls the substances entering the cell.
• D. It supports the cell's structures.

Correct answer: A

Rationale: The correct answer is A. The function of a cell membrane is to control the substances entering and leaving the cell. The cell membrane is selectively permeable, allowing it to regulate the movement of ions and molecules in and out of the cell to maintain internal balance and proper function. Choice B is incorrect because while the cell membrane does provide some structural support, its primary function is not to maintain the cell's shape. Choice C is incorrect because the cell membrane controls both the substances entering and leaving the cell, not just those entering. Choice D is incorrect as the primary function of the cell membrane is not to support the cell's structures but to regulate the movement of substances.

5. How is the plasma membrane arranged?

• A. In a single layer made of proteins
• B. In a double layer made of proteins
• C. In a single layer of phospholipids
• D. In a double layer of phospholipids

Correct answer: D

Rationale: The plasma membrane is arranged in a double layer of phospholipids, known as a phospholipid bilayer. This structure consists of two layers of phospholipid molecules with hydrophilic heads facing the exterior and hydrophobic tails facing the interior, providing a semipermeable barrier for the cell. Choice A is incorrect because the plasma membrane is not made of a single layer of proteins. Choice B is incorrect as the double layer is composed of phospholipids, not proteins. Choice C is incorrect as the plasma membrane is not made of a single layer of phospholipids but rather a double layer.

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