Tonicity in cells refers to the concentration of solute in a solution outside of a cell, relative to
The solute concentration of the cytoplasm inside the cell.
The permeability of the cell membrane.
The swelling of the cell.
The number of cell fragments inside the cell.
The presence of a cell wall.
The Correct Answer is A
Choice A rationale: The solute concentration of the cytoplasm inside the cell is correct because tonicity is a measure of how the solution affects the movement of water across the cell membrane by osmosis. Osmosis is the process by which water moves from a region of high water concentration to a region of low water concentration. The water concentration of a solution is determined by the solute concentration of the solution. The higher the solute concentration, the lower the water concentration, and vice versa. Therefore, tonicity compares the solute concentration of the solution outside the cell to the solute concentration of the cytoplasm inside the cell.
Choice B rationale: The permeability of the cell membrane is incorrect because permeability is a property of the cell membrane that determines how easily molecules can pass through it, not a measure of tonicity. The cell membrane is selectively permeable, meaning that it allows some molecules to cross, but not others. The cell membrane is permeable to water, but not to most solutes.
Choice C rationale: The swelling of the cell is incorrect because swelling is a result of tonicity, not a measure of it. Swelling occurs when a cell is placed in a hypotonic solution, which has a higher concentration of water and lower concentration of solute than the cell. In a hypotonic solution, water moves into the cell and out of the solution by osmosis, causing the cell to swell.
Choice D rationale: The number of cell fragments inside the cell is incorrect because cell fragments are pieces of broken cells that have no relation to tonicity. Cell fragments can be produced by mechanical damage, apoptosis, or necrosis, but they do not affect the solute concentration of the cytoplasm or the solution.
Choice E rationale: The presence of a cell wall is incorrect because the cell wall is a structure that surrounds the cell membrane in some cells, such as plant cells, but it does not affect tonicity. The cell wall is made of cellulose, a polysaccharide that is resistant to water. The cell wall provides mechanical support and prevents the cell from bursting in a hypotonic solution, but it does not change the solute concentration of the cytoplasm or the solution.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is B
Explanation
Choice A rationale: Sudan IV is a stain used to stain lipids. It is a red powder that dissolves in lipids and stains them red, but does not react with sugars. ¹
Choice B rationale: Benedict's is a reagent used to test for reducing sugars. It is a blue solution of copper (II) sulfate, sodium carbonate, and sodium citrate that reduces the copper (II) ions to copper (I) ions when heated with a reducing sugar, forming a red, orange, or green precipitate of copper (I) oxide. ⁴
Choice C rationale: Biuret is a reagent used to test for proteins and polypeptides. It is a blue solution of copper (II) sulfate and sodium hydroxide that forms a violet or pink complex with the peptide bonds in proteins or peptides. ⁸
Choice D rationale: Phenol red is a pH indicator. It is a red solution that changes color from yellow to red over the pH range 6.8 to 8.2, and from pink to fuchsia over 8.2 to 10.0. It does not react with sugars. ¹¹
Choice E rationale: Iodine is a reagent used to test for starch. It is a brown solution of iodine and potassium iodide that forms a blue-black complex with the starch molecules. It does not react with simple sugars. ¹⁴
Correct Answer is A
Explanation
Choice A reason: Benedict's test is a test for the presence of reducing sugars, such as glucose or maltose, in a solution. The test involves adding Benedict's reagent, which is a blue solution of copper (II) sulfate, sodium carbonate, and sodium citrate, to the solution and heating it in a water bath. If reducing sugars are present, they reduce the copper (II) ions to copper (I) ions, which form a red, orange, or green precipitate of copper (I) oxide. The color and amount of the precipitate indicate the concentration of reducing sugars in the solution. ¹
Choice B reason: Brown paper test is a test for the presence of lipids, such as fats or oils, in a solution. The test involves placing a drop of the solution on a piece of brown paper and letting it dry. If lipids are present, they leave a translucent spot on the paper, which can be seen by holding the paper against a light source. The test is based on the fact that lipids are nonpolar and do not dissolve in water, but can dissolve in organic solvents and stain the paper. ²
Choice C reason: Biuret test is a test for the presence of proteins or peptides in a solution. The test involves adding Biuret reagent, which is a blue solution of copper (II) sulfate and sodium hydroxide, to the solution. If proteins or peptides are present, they form a complex with the copper (II) ions, which changes the color of the solution to violet or pink. The test is based on the fact that proteins and peptides have peptide bonds, which have nitrogen atoms that can coordinate with the copper (II) ions. ³
Choice D reason: Iodine test is a test for the presence of starch in a solution. The test involves adding iodine solution, which is a brown solution of iodine and potassium iodide, to the solution. If starch is present, it forms a complex with the iodine molecules, which changes the color of the solution to blue-black. The test is based on the fact that starch is a polysaccharide that has a helical structure, which can trap the iodine molecules inside. ⁴
Choice E reason: Wendelspecht test is a fictional test that does not exist in reality. It is a made-up name that has no meaning or relevance to the topic of this question. Therefore, it cannot be a valid answer.
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