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You are watching: Which of the following statements about reducing sugars are true?

Organic Molecules These are complex, carbon-containing molecules linked via living organisms. Many additionally contain hydrogen and also oxygen. There are five significant types: carbohydrates, lipids, proteins, nucleic acids, and also vitamins. We spanned the first three types in lab. A testimonial of our carbohydrate test information is offered on this web page. Click the molecule kinds over to link to the associated testimonial material.

Benedict"s Reagent: A Test for Reducing Sugars Carbohydrates are split into 2 teams based on the complexity of their framework. Simple carbohydrates can create either a single ring framework (monosaccharides) or a double ring framework (disaccharides -- created once a pair of monosaccharides bond). Simple carbohydrates encompass acquainted sugars such the monosaccharides glucose (the fundamental fuel of cells) and also fructose (uncovered in fruits). Typical disaccharides include sucincreased (table sugar) and also lactose (the sugar in milk). Complex carbohydrates (polysaccharides) are chains of many bonded easy carbohydprices, and also are frequently offered for energy storage. These encompass starch, cellulose, and also glycogen. One test for the visibility of many kind of simple carbohydprices is to usage Benedict"s reagent. It transforms from turquoise to yellow or oarray once it reacts with reducing sugars. These are simple carbohydrates through unbound aldehyde or ketone groups. In lab, we supplied Benedict"s reagent to test for one particular reducing sugar: glucose.




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Interpreting Benedict"s Reagent Results Benedict"s reagent starts out aqua-blue. As it is heated in the visibility of reducing sugars, it transforms yellow to oarray. The "hotter" the last color of the reagent, the greater the concentration of reducing sugar. In basic, blue to blue-green or yellow-green is negative, yellowish to bideal yellow is a modeprice positive, and bideal ovariety is a very solid positive. (See below).
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Terminology review: Controls

Water plus Benedict"s reagent is a negative control for the sugar test. It demonstprices an unfavorable test result (no sugar present). See tube 1 above.

Glucose plus Benedict"s reagent is a positive control for the sugar test. It demonstrates what a strong positive result must look like. It likewise proves that our reagents haven"t gone bad (they are qualified of developing a positive result). See tube 4 above. The suggest of controls is twofold. They give you standards to compare against, and also they show that your reagents are functioning correctly.

Class Benedict"s Reagent Results Aside from our controls, we tested 3 services for glucose: starch, acid-treated starch, and also amylase-treated starch. As starch is a polysaccharide, it is unsurpincreasing that the starch solution tested negative for basic sugars. We mixed HCl (an acid) right into starch and re-tested for easy sugars. First, we had actually to adjust the pH of the services earlier to neutral before adding the Benedict"s reagent. We offered a pH indicator and NaOH (a base) for this. We then added the Benedict"s reagent. We got moderately positive results (orangish color). This is bereason HCl breaks starch back dvery own right into its component monosaccharides (glucose, in this case). Amylase is an enzyme that clears glucose molecules from starch. Both plants and animals use amylase once digesting starch. Unfortunately, amylase cannot break the beta-bonds which hold the glucose molecules together in cellulose. (If it can, we"d have the ability to eat hay). Based on this indevelopment, have the right to you number out what our outcomes should be if we tested amylase-treated starch and also amylase-treated cellulose solutions for reducing sugars?