The biuret test would indicate a positive result for proteins in which of the following solutions?
Starch solution
Olive oil
Albumin solution
Distilled water
Glucose solution
The Correct Answer is C
Choice A rationale: Starch solution is not a protein solution, but a carbohydrate solution. Starch is a polysaccharide, which is a polymer of glucose molecules. Starch does not contain peptide bonds, which are the bonds that link amino acids in proteins. Therefore, starch solution would not react with the biuret reagent and would not produce a violet color.
Choice B rationale: Olive oil is not a protein solution, but a lipid solution. Olive oil is mainly composed of triglycerides, which are esters of glycerol and fatty acids. Olive oil does not contain peptide bonds, which are the bonds that link amino acids in proteins. Therefore, olive oil would not react with the biuret reagent and would not produce a violet color.
Choice C rationale: Albumin solution is a protein solution. Albumin is a globular protein that is found in blood plasma and egg white. Albumin contains many peptide bonds, which are the bonds that link amino acids in proteins. Therefore, albumin solution would react with the biuret reagent and would produce a violet color.
Choice D rationale: Distilled water is not a protein solution, but a pure solvent. Distilled water is water that has been purified by boiling and condensing. Distilled water does not contain any solutes, such as proteins, carbohydrates, or lipids. Therefore, distilled water would not react with the biuret reagent and would not produce a violet color.
Choice E rationale: Glucose solution is not a protein solution, but a carbohydrate solution. Glucose is a monosaccharide, which is a simple sugar. Glucose does not contain peptide bonds, which are the bonds that link amino acids in proteins. Therefore, glucose solution would not react with the biuret reagent and would not produce a violet color.
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 rationale: Movable is correct because motile is an adjective that describes the ability of an organism or a cell to move by itself, using some form of locomotion, such as flagella, cilia, or pseudopodia. For example, some bacteria, protists, and sperm cells are motile.
Choice B rationale: Fixed is incorrect because fixed is the opposite of motile. Fixed is an adjective that describes the inability of an organism or a cell to move by itself, due to being attached to a substrate or a surface. For example, some plants, fungi, and coral are fixed.
Choice C rationale: Magnification is incorrect because magnification is not related to motility. Magnification is a measure of how much larger an image appears compared to the actual size of the object. Magnification is used in microscopy to observe small objects, such as cells.
Choice D rationale: Solid is incorrect because solid is not related to motility. Solid is a state of matter that has a definite shape and volume, due to the strong attraction between the molecules. Solid is contrasted with liquid and gas, which have no definite shape and can flow.
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