Reducing and non-reducing sugars tests.
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REDUCING and NON-REDUCING sugars tests. Aim: To distinguish which of the four unknown given substances are sucrose, maltose, glucose and water. Apparatus: Safety: For this experiment I made sure all the glassware was away from the edge of the table to avoid knocking them off and smashing them. Also I was careful whilst boiling the solutions and I was careful carrying to and from the water bath. I wore safety goggles throughout the experiment. Method: NON-REDUCING sugar. * Add 2cm of one of the unknown solutions into a test tube * Add 2cm of benedict's solution * Repeat this with each of the unknown solutions * Heat all the solutions in the water bath for 2 minutes Look at the colour of the solution if it remains the original blue colour of the benedict's solution then proceed with the test for REDUCING sugars.
A and C and then proceeded to the REDUCING sugars test the results were as following: SOLUTION COLOUR AFTER NON-REDUCING SUGAR AND REDUCING SUGAR TESTS A RED C BLUE From my results I can tell: SOLUTION NAME A SUCROSE B GLUCOSE C WATER D MALTOSE Conclusion: Reducing or non-reducing refers to whether a carbohydrate gives a positive or negative test towards the weakly oxidizing Cu in benedict's solution. All reducing sugars contain free or potentially free aldehde. Only sugars that can't open to the carbonyl form are non-reducing. The Benedict's test allows us to detect the presence of reducing sugars (sugars with a free aldehyde or ketone group). All monosaccharides (carbohydrates that can't be hydrolysed to simpler compounds)
We know that sucrose is made up of one glucose molecule and one fructose molecule glycosidicaly bonded. After hydrolysing to break the glycosidic bond to its constituent monosaccharides it then gave a positive test for reducing sugars (benedict's test). Solution B was glucose as it formed a red precipitate, which showed it was a monosaccharide solution. Solution C was water it also remained its original blue colour however after hydrolysing it still gave a negative test for reducing sugars (benedict's test). Finally, solution D was maltose as it left a green precipitate. Maltose is also a disaccharide, as previously explained not all disaccharides are non-reducing; however they are not as reducing as monosaccharides. My final conclusion is that the reducing sugars include all monosaccharides, glucose and fructose and some disaccharides, maltose. Tegan Gowlland
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The author has a sound understanding of the biochemistry behind this straightforward experiment. However, muddling up the tests for reducing and non-reducing sugars suggests that the finished write up was not checked. Greater attention to detail generally would have improved the quality.
Marked by teacher Adam Roberts 05/09/2013
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