Which reagent is used to detect the presence of protein?
Sudan IV
Benedict's
Biuret
Iodine
The Correct Answer is C
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.
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 B
Explanation
Choice A rationale: Hypotonic is incorrect because hypotonic is a type of solution that has a higher concentration of water and lower concentration of solute than the cell placed in the solution. In a hypotonic solution, water moves into the cell and out of the solution by osmosis, causing the cell to swell.
Choice B rationale: Isotonic is correct because isotonic is a type of solution that has the same concentration of water and solute as the cell placed in the solution. In an isotonic solution, there is no net movement of water across the cell membrane.
Choice C rationale: Diffusive is incorrect because diffusive is an adjective that describes the movement of molecules from a region of high concentration to a region of low concentration, not a type of solution. Diffusion is the process by which molecules move across a membrane or a space due to their random motion.
Choice D rationale: Osmotic is incorrect because osmotic is an adjective that describes the movement of water across a semipermeable membrane, not a type of solution. Osmosis is the process by which water moves from a region of high water concentration to a region of low water concentration.
Choice E rationale: Hypertonic is incorrect because hypertonic is a type of solution that has a lower concentration of water and higher concentration of solute than the cell placed in the solution. In a hypertonic solution, water moves out of the cell and into the solution by osmosis, causing the cell to shrink.
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