When Elodea leaves were placed in 10% NaCl, what was the result?
The cell membrane did not change at all because of the protection of the cell wall.
The cells burst because the solution was hypotonic.
The cell membrane shrank, but the central vacuole remained full.
The cell membrane shrank away from the cell wall because the solution was hypertonic.
The cell became turgid.
The Correct Answer is D
Choice A rationale: The cell membrane did not change at all because of the protection of the cell wall is incorrect because the cell wall does not prevent the movement of water across the cell membrane. The cell wall only provides mechanical support and prevents the cell from bursting in a hypotonic solution.
Choice B rationale: The cells burst because the solution was hypotonic is incorrect because the solution was hypertonic, not hypotonic. A hypertonic solution has a lower concentration of water than the cell, so water moves out of the cell and into the solution by osmosis, causing the cell to shrink.
Choice C rationale: The cell membrane shrank, but the central vacuole remained full is incorrect because the central vacuole also loses water in a hypertonic solution. The central vacuole is a large organelle that stores water and other substances in the plant cell. When water leaves the cell, the central vacuole shrinks and the cell loses its turgor pressure.
Choice D rationale: The cell membrane shrank away from the cell wall because the solution was hypertonic is correct because this is what happens when a plant cell is placed in a hypertonic solution. The cell membrane and the cytoplasm contract and pull away from the cell wall, creating a gap between them. This is called plasmolysis and it can damage the cell.
Choice E rationale: The cell became turgid is incorrect because the cell becomes turgid in a hypotonic solution, not a hypertonic one. A hypotonic solution has a higher concentration of water than the cell, so water moves into the cell and out of the solution by osmosis, causing the cell to swell and press against the cell wall. This is called turgor and it helps the cell maintain its shape and rigidity.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
Choice A rationale: A hypertonic solution has a higher solute concentration than the potato cell, which means it has a lower water potential. Water will move out of the potato cell by osmosis, causing it to shrink and become soft and limp.
Choice B rationale: A hypotonic solution has a lower solute concentration than the potato cell, which means it has a higher water potential. Water will move into the potato cell by osmosis, causing it to swell and become turgid and firm.
Choice C rationale: An isotonic solution has the same solute concentration as the potato cell, which means it has the same water potential. Water will move in and out of the potato cell at the same rate, causing it to remain unchanged in size and shape.
Choice D rationale: Tonic is not a valid term to describe the solute concentration of a solution. The correct terms are hypertonic, hypotonic, or isotonic.
Choice E rationale: I cannot determine anything without comparing multiple solutions is incorrect because the appearance of the potato slice after soaking in the solution provides enough information to determine the relative solute concentration of the solution.
Correct Answer is C
Explanation
Choice A rationale: Sudan IV is not a reagent for protein detection, but a reagent for lipid detection. Sudan IV is a red dye that binds to non-polar molecules, such as fats and oils. Sudan IV stains lipids red, while leaving water-soluble molecules, such as proteins, unstained¹.
Choice B rationale: Benedict's is not a reagent for protein detection, but a reagent for sugar detection. Benedict's is a blue solution that contains copper sulfate, sodium carbonate, and sodium citrate. Benedict's reacts with reducing sugars, such as glucose and fructose, and reduces the copper ions from blue to orange-red².
Choice C rationale: Biuret is a reagent for protein detection. Biuret is a blue solution that contains copper sulfate and sodium hydroxide. Biuret reacts with peptide bonds, which are the bonds that link amino acids in proteins. Biuret changes color from blue to violet when it binds to protein molecules³.
Choice D rationale: Iodine is not a reagent for protein detection, but a reagent for starch detection. Iodine is a brown solution that forms a complex with starch, a polysaccharide composed of glucose units. Iodine changes color from brown to blue-black when it interacts with starch molecules⁴.
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