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benedict's test for reducing sugars a level essay report
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Title : Comparison of Chemical Composition of Various Food Stuff
Introduction
Carbohydrate is a macromolecule that consists of atoms of carbon, hydrogen & oxygen. The carbohydrates or saccharides exists in 4 groups, monosaccharides, disaccharides, oligosaccharides and polysaccharides. Starch is among one of the polysaccharides and it consists of a large number of units of glucose molecules joined together by glycosidic bonds. Starch consists of two types of molecules , the linear and helical amylose and the branched amylopectin. Potatoes have large amount of starch as it is a staple food. The starch in potato can be tested by the iodine test. When starch is present, the iodine will turn purplish black in colour.
Benedict’s solution is used to test the presence of reducing sugar. All monosaccharides are reducing sugars since all of them have an active carboxyl group. The example of reducing sugars are glucose, fructose, lactose and maltose. Some disaccharides that are exposed to a carboxyl group are also reducing sugar, but less reactive than monosaccharides. By mixing the sugar solution solution with Benedict’s solution and heating them under water bath of 80℃, a redox reaction will occur. The copper(II) sulphate present in Benedict’s solution which exists as light blue in colour reacts with electron from aldehyde or ketose group of reducing sugars to form copper oxide, which is a brick-red precipitate.
The purpose of doing Benedict’s test is to detect the presence of reducing sugar in a substance. Benedict’s solution, which is the reagent for the test will detect the presence of aldehydes and alpha-hydroxy-ketones. If positive result is shown when Benedict’s test was conducted, the substance will change in colour from c...
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9. http://zoologistbd.blogspot.com/2012/04/benedicts-test-for-reducing-sugars.html
10. Omar Nahhas, Yahoo Contributor Network ( 22 July, 2009 ). Retrieved 15 May 2014, from http://voices.yahoo.com/the-chemical-constituents-living-matter-3856864.html
11. Retrieved 15 May 2014, from http://en.wikipedia.org/wiki/Protein
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13. Jones, M. & Taylor, D. (2007). AS Level and A Level Biology: Second Edition. Cambridge: Cambridge University Press.
14. Starch,retrieved 18th May 2014. http://en.wikipedia.org/wiki/Starch
15. Iodine test,retrieved 18th May 2014. http://en.wikipedia.org/wiki/Iodine_test
16. Retrieved 18th May 2014. http://www.elmhurst.edu/~chm/vchembook/547starch.html
17. Retrieved 18th May 2014. http://en.wikipedia.org/wiki/Carbohydrate
To uncover organic compounds like carbohydrates, lipids, proteins and nucleic acid, by using tests like Benedict, Lugol, Biuret and Beta Carotene. Each test was used to determine the presents of different organic molecules in substances. The substances that were tested for in each unknown sample were sugars, starches, fats, and oils. Moreover, carbohydrates are divided into two categories, simple and complex sugars. Additionally, for nonreducing sugars, according to Stanley R. Benedict, the bond is broken only by high heat to make make the molecules have a free aldehydes (Benedict). As for Lipids, there are two categories saturated and unsaturated fats. One of the difference is that saturated fats are mostly solids and have no double bond (Campbell Biology 73). The Beta Carotene test works by dissolving in a lipid, thus giving it color to make it visible. Moreover, proteins are made out of amino acids that are linked by a polypeptide bond (Campbell Biology 75). The purpose of this experiment was to determine whether an unknown class sample or food sample had any carbohydrates, lipids, or proteins in it. The expected result of the lab was that some substances would be present while other would be absent.
Cain, M. L., Urry, L. A., & Reece, J. B. (2010). Campbell Biology. Benjamin Cummings.
2)Campbell, Neil A., and Jane B. Reece. Biology. San Francisco, CA: Benjamin Cummings, 2008. Print.
The unknown substance is probably a carbohydrate because it tested positive for starch which is a polysaccharide. This reaction also had very similar results as the Lugol’s test for potatoes which is a polysaccharide. Although the colors from the test for potatoes were not the same colors as the test for the unknown; the Biuret test had a slight color change and the Lugol’s test had a dramatic color change for both the unknown and potatoes. I am sure that the unknown was a starch, but the Benedict’s test for sugar was positive for the potatoes while the Benedict’s test for the unknown didn’t have a color change. The unknown probably did not have a color change for the Benedict’s test simply because there were not enough sugar present in the unknown for it to test positive. The Sudan IV Test for Lipids did not test positive for the unknown nor the potatoes because there isn’t a trace of lipids in starch. Based on my results, the unknown has a little protein, a lot of starch and no traces of lipids or
Iodine is used to distinguish starch from mono/di/polysaccharides. In the test only two of the six solutions showed any signs of starch being present. The potato juice turned a brownish color with a precipitate indicating a slight presence of starch. The stach solution turned a dark blue/black color indicating a very high presence of starch in the solution. The presence of starch in the potato juice indicates that it does not have as high an amount of carbohydrates as onion juice, but a higher concentration of starch.
Miller, K. R., & Levine, J. S. (2010). Miller & Levine biology. Boston, Mass.: Pearson.
One of the four molecules is carbohydrates. Carbohydrates are made out of CHO. The main building blocks are sugars (saccharides). What carbohydrates do for us is they store fuel for our cells. They are fast energy. Glucose, fructose, and galactose are examples of single or simple sugar molecules or monosaccharide. Maltose, sucrose, and lactose are examples of two sugar molecules linked, also known as disaccharide. Starch, glycogen, and cellulose are examples of many sugar molecules linked. They are also called polysaccharide. If you wanted to test if there were carbohydrates in something you could do the sugar or the starch test.
The purpose of the experiment is to test the specificity of the enzyme lactase. To test the specificity we used lactose and sucrose and checked for glucose in the solution. The next procedure in our experiment is to test for pH and environmental factors and their effects on lactase. We then tested lactase with lactose in contrasting environments and temperatures. The prediction made for specificity was that lactase was only specific to lactose. We also concluded that sucrose and lactose as well as sucrose and water solution would be the highest concentration for glucose.
5 Jones, M. , Fosbery, R. , Taylor, Dennis. , (2007), Biology 1, Cambridge University Press, Cambridge
Two unknown solutions were given to conduct a lab, to determine the macromolecules within them by conducting a series of macromolecule tests. The unknown solution which will be discussed is Solution #1 as shown in Table #2; this solution was known as Unknown #2. The solution was of a watery consistency; it was transparent yet had a pinkish hue to it. There were no visible grains in the solution, unlike other solutions that could not fully dissolve certain products. The Fats test, Protein test, Starch test and Glucose test were conducted to identify the types of macromolecules in the solution. The Fats test, Protein test, and Starch test all came out negative. This was concluded by following the negative observations of these tests from Table #1. The only test that came
Miller, K. R., & Levine, J. S. (2010). Miller & Levine biology. Boston, Mass: Pearson
3. Benedict’s test, which uses Benedict’s reagent, (usually used to test for the presence of reducing sugars) will show up positive in the presence of all monosaccharaides and some disaccharides. The test will also show a positive in the presence of aldehydes and alpha-hydroxy-ketones. Benedict’s test is not positive for sucrose because the glycosidic bond between the fructose and the glucose (the two monosaccharaides making up sucrose) prevents the isomerization of glucose into aldehydes and fructose into alpha-hydroxy-ketones. Therefore sucrose is a non-reducing sugar and these do not react with Benedict’s reagent. Since the test is designed for use with monosaccharaides glucose gives a positive result, as it is one. In conclusion glucose is a monosaccharaide sugar while sucrose is a disaccharide made of two monosaccharaide sugars.
3 Leicht B. G., McAllister B.F. 2014. Foundations of Biology 1411, 2nd edition. Southlake, TX: Fountainhead Press. Pp 137, 163-168, 177-180,
Michener, William K. and Haeuber, Richard A., Bioscience. American Institute of Biological Science. Sep98. Vol. 48. Issue 9. p677.
Campbell, N. A. & J. B. Reece, 8th eds. (2008). Biology. San Francisco: Pearson Benjamin Cummings.