Starch





Starch 3453
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Starch is the chief storage form of carbohydrate in plants and the most important source of carbohydrate in human nutrition. A starch molecule is a polysaccharide assembled from the simple sugar glucose ; it can contain anywhere from five hundred to several hundred thousand glucose molecules joined by covalent bonds into a single structure. In addition to its importance in human nutrition, starch has many industrial applications: it is used in the manufacture of paper, textiles, pharmaceuticals, and biodegradable polymers, and it is an additive in foods.

Chemically, starch is composed of two different molecules, amylose and amylopectin. In amylose, the glucose molecules are linked in a "linear" fashion; however, the tetrahedral chemistry of carbon (and the bond angles that result from this chemistry) gives amylose an overall spiral shape. Amylopectin, on the other hand, has a linear arrangement of glucose molecules that includes, at regular intervals, a different kind of linkage between two adjacent glucoses. This different linkage results in the formation of a branched structure and an overall treelike shape for this molecule. Plant starch is typically 20 to 30 percent amylose and 70 to 80 percent amylopectin. The classic test for the presence of starch is reaction with iodine. If starch molecules are present in a substance, the addition of iodine yields a deep blue color, which results from I 2 being trapped inside the spiral structures of amylose molecules.

Starch molecules are broken down by enzymes known as amylases. The digestibility of a specific starch is influenced by its physical form. In plants starch is present in microscopic granules, which impair the enzymatic digestion of starch molecules obtained from plants. Cooking starch-containing items results in the hydration of starch molecules and the swelling of starch granules, increasing the rate and enhancing the enzymatic breakdown of starch. Amylases also convert starch to glucose.

SEE ALSO Carbohydrates ; Polysaccharides .

Matthew A. Fisher

Bibliography

Atkins, Peter W. (1987). Molecules. New York: W.H. Freeman.

Hancock, Robert D., and Tarbet, Bryon J. (2000). "The Other Double Helix—The Fascinating Chemistry of Starch." Journal of Chemical Education 77: 988–992.

Internet Resources

Department of Polymer Science, University of Southern Mississippi. Starch. Available from http://www.psrc.usm.edu/macrog/ .

Holmes, ZoeAnn. Oregon State University. Starch. Available from http://osu.orst.edu/instruct/ .



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Dec 9, 2010 @ 10:22 pm
i need some imformation about starch and i am study in 12th standard
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Nov 17, 2011 @ 3:03 am
What is the difference of esterified and oxidized starch in terms of chemical structure?
Innocent
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Jun 14, 2012 @ 2:14 pm
Hi, I have just discovered this book and have steratd on the no starch diet. i am in agony with I.B.S and ankylosing. I am in terrible pain and am in kind of a burnout because of it all. My urine is also burning so much and I am having difficulty in sleeping. I have been taken off all heavy medication and now not coping with pain. I have been on no starch for nearly a week. Can you tell me when will I get some release from this terrible pain? How long does it take to settle. Can't take pain relief for it burns my tummy. I just need so much encouragement. Thank you so much for opening my eyes to what has been going on. Anything else that you can give to me or help I will be so grateful,Many thanks, I would love to hear from someone. Trish Bussell.

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