When testing tonicity in Elodea cells, once Elodea cells were placed in distilled water, what did you observe? Select all that apply.
Cell membranes pressed tightly against the cell walls.
Many of the cells had burst.
Full central vacuoles.
Many of the cells had become crenated.
Correct Answer : A,C
Choice A rationale: Cell membranes pressed tightly against the cell walls is correct because this is what happens when a plant cell is placed in a hypotonic solution. 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.
Choice B rationale: Many of the cells had burst is incorrect because plant cells do not burst in a hypotonic solution, unlike animal cells. Plant cells have a rigid cell wall that prevents them from bursting, even when they are full of water. The cell wall can withstand the pressure of water entering the cell.
Choice C rationale: Full central vacuoles is correct because this is also what happens when a plant cell is placed in a hypotonic solution. The central vacuole is a large organelle that stores water and other substances in the plant cell. When water enters the cell, the central vacuole expands and fills up the cell, increasing its turgor pressure.
Choice D rationale: Many of the cells had become crenated is incorrect because crenation is the opposite of what happens in a hypotonic solution. Crenation is the process by which a cell shrinks and becomes wrinkled due to water loss in a hypertonic solution. 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.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
Choice A rationale: Carbon dioxide is not a product of the light reaction, but a reactant of the dark reaction. The light reaction does not use carbon dioxide, but water and light energy to produce ATP, NADPH, and oxygen¹.
Choice B rationale: NADPH is a product of the light reaction. It is an electron carrier that is reduced by the electrons from water in photosystem I. NADPH provides electrons and hydrogen for the dark reaction².
Choice C rationale: ATP is a product of the light reaction. It is an energy molecule that is synthesized by the enzyme ATP synthase using the proton gradient created by the electron transport chain. ATP provides energy for the dark reaction³.
Choice D rationale: Oxygen is a product of the light reaction. It is released as a by-product of the splitting of water in photosystem II. Oxygen is either used for cellular respiration or released into the atmosphere⁴.
Choice E rationale: Energy intermediates are not a specific product of the light reaction, but a general term for molecules that store energy or electrons, such as ATP and NADPH. Therefore, this choice is not incorrect, but less specific than choice A⁵.
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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