Starch Hydrolysis by Amylase
Experiment 2: Starch Hydrolysis by Amylase
Theoretical Background
Polymers of carbohydrates are called polysaccharides, and make up some of the most important naturally occurring compounds [1]. They have thousands of monosaccharide units linked to each other by oxygen bridges. They include starch, glycogen, and cellulose, all three of which yield only glucose when completely hydrolyzed [2].
A
B
Figure 1. Starch (amylose) (A) and cellulose (B)
Starch occurs naturally in plants, which use it to storage glucose units for energy. It is often found in seeds and tubers (e.g., potatoes). It consists of two kinds of polymers of glucose. The simpler kind is called amylose, and it makes up about 20% of starch. It is basically a chain of glucose units linked by α – 1,4 – glycosidic bonds. During digestion, the oxygen bridges are hydrolyzed and the glucose units are broken up. 80% of starch is a water insoluble fraction called amylopectin [2], which is a branched chain polysaccharide with again α – 1,4 – glycosidic bonds. At approximately every 25 glucose units, a branching of glucose units, exists. Upon treatment with acid or under the influence of enzymes, the components of starch are hydrolyzed progressively to dextrins (mixture of low melting polysaccharides, made up of 3 – 8 glucose units), maltose and finally D-glucose [3].
Starch obtained by animals from plants is stored in the animal body in the form of glycogen. Digestive processes in both plants and animals convert starch to glucose, a source of energy. Starch is one of the major nutrients in the human died. Its presence in foods and other substances can be detected by the blue-black color produced when iodine solution is added to a sample of the material to be tested [5].
Starch + I2 blue-black color
Amylase enzyme
Proteins which catalyze the chemical reactions are called enzymes. Non-biological catalysts work at wide ranges of temperature and pH,
Theoretical Background
Polymers of carbohydrates are called polysaccharides, and make up some of the most important naturally occurring compounds [1]. They have thousands of monosaccharide units linked to each other by oxygen bridges. They include starch, glycogen, and cellulose, all three of which yield only glucose when completely hydrolyzed [2].
A
B
Figure 1. Starch (amylose) (A) and cellulose (B)
Starch occurs naturally in plants, which use it to storage glucose units for energy. It is often found in seeds and tubers (e.g., potatoes). It consists of two kinds of polymers of glucose. The simpler kind is called amylose, and it makes up about 20% of starch. It is basically a chain of glucose units linked by α – 1,4 – glycosidic bonds. During digestion, the oxygen bridges are hydrolyzed and the glucose units are broken up. 80% of starch is a water insoluble fraction called amylopectin [2], which is a branched chain polysaccharide with again α – 1,4 – glycosidic bonds. At approximately every 25 glucose units, a branching of glucose units, exists. Upon treatment with acid or under the influence of enzymes, the components of starch are hydrolyzed progressively to dextrins (mixture of low melting polysaccharides, made up of 3 – 8 glucose units), maltose and finally D-glucose [3].
Starch obtained by animals from plants is stored in the animal body in the form of glycogen. Digestive processes in both plants and animals convert starch to glucose, a source of energy. Starch is one of the major nutrients in the human died. Its presence in foods and other substances can be detected by the blue-black color produced when iodine solution is added to a sample of the material to be tested [5].
Starch + I2 blue-black color
Amylase enzyme
Proteins which catalyze the chemical reactions are called enzymes. Non-biological catalysts work at wide ranges of temperature and pH,
References: 1. Morrison, R.T., and Boyd, R.N., Organic Chemisty, 6th Ed., Prentice Hall, New Jersey, 1992 2 4. Perona, M., Analysis of Foods for Starch and Vitamin C, 2000 http://science.csustan.edu/perona/2000/Exp8/bkg.htm 5. Starch, The Columbia Electronic Encyclopedia, Columbia University Press, 2003 http://reference.allrefer.com/encyclopedia/S/starch.html 6. Amylase, GreenWood Health Inc., 2003 http://greenwoodhealth.net/np/amylase.htm