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Starch is a polysaccharide 1.Is starch positive in Bial‘s test？（what color ？） 2.Is starch positive in （Seliwanoff‘s）ketohexoses test？（what color would it be if negative）

Starch is a polysaccharide 1.Is starch positive in Bial‘s test？（what color ？） 2.Is starch positive in （Seliwanoff‘s）ketohexoses test？（what color would it be if negative）

Biochemistry
Biochemistry
9th Edition
ISBN:9781319114671
Author:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.
Publisher:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.
Chapter1: Biochemistry: An Evolving Science
Section: Chapter Questions
Problem 1P
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Starch is a polysaccharide 1.Is starch positive in Bial‘s test？（what color ？） 2.Is starch positive in （Seliwanoff‘s）ketohexoses test？（what color would it be if negative）
**Testing for Sugars: Bial’s and Resorcinol (Selivanoff's) Tests** **1. Bial’s Test (Distinguishing between Pentoses and Hexoses):** - Used to identify pentoses. - Procedure: - Add 0.5 mL of a 1% carbohydrate solution in water to 1 mL of Bial's reagent. - Use a glass Pasteur pipette and avoid mechanical pipetting. - Place in a boiling water bath for 2 minutes. - Results: - A blue-green colored product indicates the presence of pentoses. - A yellow-green color indicates hexoses, nucleotides, or disaccharides. **2. Resorcinol (Selivanoff's) Test (Ketoses):** - Used to test for ketoxoses. - Procedure: - Add 0.1 mL of a 1% carbohydrate solution in water to 1 mL of the reagent. - Heat the solution in a boiling water bath for 5 minutes. - Results: - A deep red colored precipitate within 5 minutes indicates ketoxoses. - Sucrose gives a positive ketoxose test due to partial hydrolysis into glucose and fructose. - Other sugars turn red upon prolonged heating. **Annotations on the Document:** - Handwritten notes mention "Structure of the product the resorcinol & ketoxes give red color upon unknown why blue." - Chemical structure depicted: "H-C=CH-O". These tests help in distinguishing between different types of sugars by observing color changes under specific conditions.
Transcribed Image Text:**Testing for Sugars: Bial’s and Resorcinol (Selivanoff's) Tests** **1. Bial’s Test (Distinguishing between Pentoses and Hexoses):** - Used to identify pentoses. - Procedure: - Add 0.5 mL of a 1% carbohydrate solution in water to 1 mL of Bial's reagent. - Use a glass Pasteur pipette and avoid mechanical pipetting. - Place in a boiling water bath for 2 minutes. - Results: - A blue-green colored product indicates the presence of pentoses. - A yellow-green color indicates hexoses, nucleotides, or disaccharides. **2. Resorcinol (Selivanoff's) Test (Ketoses):** - Used to test for ketoxoses. - Procedure: - Add 0.1 mL of a 1% carbohydrate solution in water to 1 mL of the reagent. - Heat the solution in a boiling water bath for 5 minutes. - Results: - A deep red colored precipitate within 5 minutes indicates ketoxoses. - Sucrose gives a positive ketoxose test due to partial hydrolysis into glucose and fructose. - Other sugars turn red upon prolonged heating. **Annotations on the Document:** - Handwritten notes mention "Structure of the product the resorcinol & ketoxes give red color upon unknown why blue." - Chemical structure depicted: "H-C=CH-O". These tests help in distinguishing between different types of sugars by observing color changes under specific conditions.
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