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.
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Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is D
Explanation
Choice A rationale: An isotonic solution has the same solute concentration as the plant cells, which means it has the same water potential. Water will move in and out of the plant cells at the same rate, causing them to remain unchanged in size and shape. This will not help the lettuce to become less wilted.
Choice B rationale: A hypertonic solution has a higher solute concentration than the plant cells, which means it has a lower water potential. Water will move out of the plant cells by osmosis, causing them to shrink and become plasmolysed. This will make the lettuce more wilted and not crisper.
Choice C rationale: Soaking the lettuce in water would have an effect, depending on the relative solute concentration of the water and the plant cells. Water will move across the cell membrane by osmosis, either into or out of the plant cells, causing them to change in size and shape.
Choice D rationale: A hypotonic solution has a lower solute concentration than the plant cells, which means it has a higher water potential. Water will move into the plant cells by osmosis, causing them to swell and become turgid. This will make the lettuce crisper and more appealing.
Choice E rationale: A hypotonic solution will cause the plant cells to gain water and become turgid, not more wilted. Wilted lettuce is caused by the loss of water from the plant cells, which makes them flaccid and soft.
Correct Answer is D
Explanation
Choice A rationale: Locates the specimen is incorrect because the fine adjustment knob does not help to find the specimen on the slide, but rather to adjust the focus of the specimen. The fine adjustment knob is a small knob that is located on the side of the microscope, next to the coarse adjustment knob. The fine adjustment knob is used to make small changes in the distance between the objective lens and the specimen, which improves the sharpness of the image.
Choice B rationale: All of the answer choices are correct is incorrect because only one of the answer choices is correct. The fine adjustment knob only fine-tunes the focus of the specimen, not locates the specimen or the focus plane.
Choice C rationale: Locates the focus plane is incorrect because the fine adjustment knob does not help to find the focus plane, but rather to adjust the focus of the specimen. The focus plane is the plane that is perpendicular to the optical axis of the microscope and passes through the focal point of the objective lens. The focus plane is where the specimen is in focus and the image is clear.
Choice D rationale: Fine-tunes the focus is correct because the fine adjustment knob is used to fine-tune the focus of the specimen, which means to make small adjustments in the focus to obtain the best image quality. The fine adjustment knob is used after the coarse adjustment knob, which is used to bring the specimen into approximate focus.
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