6 . Benedict\'s solution contains Copper, which can accept electrons from reduci

Question

6 . Benedict's solution contains Copper, which can accept electrons from reducing sugars and consequently change color. A positive Benedict's sugar test will produce an orange to brick-red color. Reducing sugars have either a free aldehyde functional group or a free ketone functional group as part of their molecular structure; starches and other polysaccharides lack these functional groups. If Benedict's test changes color ( pos. reaction ) polysaccharides must be hydrolyzed

Benedict's test uses a chemical which will react with reducing sugars (like glucose and fructose) to produce a precipitate. Since sucrose and starch are not reducing sugars, Benedict's test will be negative for them. However, the hydrolysis of sucrose produces glucose and fructose, both reducing sugars. So, if sucrose has been hydrolyzed, there will be reducing sugars present which will react with Benedict's reagent to give you a positive test. Similarly, hydrolysis of starch produces glucose which will react with Benedict's reagent

7.  Iodine reacts or forms a complex with native unhydrolyzed starch molecule giving you a characteristic blue color. If starch is completely hydrolyzed, the color will disappear, Alternatively it will fade to different degrees depending upon the rate/degree of starch hydrolysis.

I do not recall the exact nature of benedicts test, If it is meant for estimating reducing sugars, it will give you a positive test, since glucose, which is a reducing sugar will be release upon starch hydrolysis. Remember, even small oligosaccharides from hydrolysis will also give you a positive test since they will have a reducing end.

Explanation / Answer

E. Hydrolysis of disaccharides and polysaccharides Result Sucrose + H20 Sucrose + HCl Starch + H20 Sucrose + HCI 1. Iodine 2. Benedict's test 3. Hydrolysis Yes/No Questions and Problems Q6. How do the results of Benedict's test indicate that hydrolysis of sucrose and starch occurred? Its of the iodine test indicate that hydrolysis of starch occurred?

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