{"id":100,"date":"2023-04-20T13:19:35","date_gmt":"2023-04-20T13:19:35","guid":{"rendered":"https:\/\/test-hcc-press-wp-multisite.pantheonsite.io\/bsc2010l\/?post_type=chapter&p=100"},"modified":"2025-10-29T16:34:00","modified_gmt":"2025-10-29T16:34:00","slug":"analysis-of-carbohydrates","status":"publish","type":"chapter","link":"https:\/\/pressbooks.hcfl.edu\/Bio1LabManual\/chapter\/analysis-of-carbohydrates\/","title":{"raw":"Chapter 4 - Analysis of Carbohydrates","rendered":"Chapter 4 – Analysis of Carbohydrates"},"content":{"raw":"
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Analysis of Carbohydrates<\/h2>\r\n

BACKGROUND<\/h3>\r\n[pb_glossary id=\"236\"]Carbohydrates[\/pb_glossary] are one of the major groups of organic molecules that make up the cell, along with proteins, lipids and nucleic acids. They are primarily responsible for the storage of energy within the cell, but they also aid in the structural support of tissues. They are commonly referred to as sugars, starches, or fibers. Carbohydrates include monosaccharides, disaccharides, and polysaccharides.<\/span>\r\n\r\n<\/div>\r\n
\r\n\r\n[pb_glossary id=\"237\"]Monosaccharides[\/pb_glossary]<\/strong> are the most basic unit of carbohydrates. They are the simplest of the sugars and consist of a single sugar unit called a [pb_glossary id=\"238\"]monomer[\/pb_glossary]<\/strong>. The functional group characteristic of monosaccharides is the aldehyde group (H-C=O). Aldehydes tend to become [pb_glossary id=\"239\"]oxidized<\/strong> [\/pb_glossary](lose an electron through donation of a hydrogen) and cause the [pb_glossary id=\"240\"]reduction[\/pb_glossary] of another molecule. Monosaccharides are usually colorless, water-soluble, crystalline solids. Some have a sweet taste. Examples include glucose (dextrose), fructose, and galactose. Monosaccharides are the building blocks of disaccharides (sucrose) and polysaccharides (cellulose and starch).\r\n\r\n[pb_glossary id=\"241\"]Disaccharides[\/pb_glossary]<\/strong> are two monosaccharides chemically bonded together. They are formed when two monomers are joined together by a [pb_glossary id=\"242\"]dehydration reaction[\/pb_glossary] (also called a condensation reaction) and a molecule of water is removed. Examples include lactose (made from glucose and galactose) and sucrose (made from glucose and fructose).\r\n\r\n[pb_glossary id=\"243\"]Polysaccharides[\/pb_glossary]<\/strong> are [pb_glossary id=\"244\"]polymers[\/pb_glossary]<\/strong> composed of many monosaccharides chemically bonded together. [pb_glossary id=\"245\"]Starch[\/pb_glossary] and [pb_glossary id=\"246\"]glycogen[\/pb_glossary] are polysaccharides that usually consist of several hundred to several thousand glucose units. Glycogen is the storage form of energy in the animal body. Plants and other organisms store their energy in the form of starch. The chains of glucose units are highly branched in glycogen compared to starch. Both starch and glycogen must be broken down into individua* glucose molecule to become available as an energy source in the cells. [pb_glossary id=\"247\"]Cellulose[\/pb_glossary] is also a polysaccharide composed of glucose subunits and is classified as a fiber. It is the primary constituent of plant cells, present in vegetables, fruits, and legumes. Cellulose differs from starch in the orientation of the bonds between the subunits of glucose.\r\n\r\n \r\n\r\n<\/div>\r\nDigestion of carbohydrates begins in the mouth with the secretion of the enzyme amylase from the serous cells of the salivary gland. Amylase breaks starch and glycogen into disaccharides. The salivary glands are grouped into three categories: parotid, submandibular, and sublingual. The stomach works to mix and churn the food, which aids in further breakdown, but has no enzyme for the digestion of carbohydrates. The majority of the digestion of carbohydrates takes place in the small intestine. As the food moves into the duodenum, an enzyme called pancreatic [pb_glossary id=\"250\"]amylase[\/pb_glossary] is released through the pancreatic duct which reduces starch and glycogen into disaccharides. Specific enzymes then work to finish the job. [pb_glossary id=\"251\"]Maltase[\/pb_glossary]<\/strong> breaks maltose into two units of glucose, sucrase breaks sucrose into glucose and fructose, and [pb_glossary id=\"252\"]lactase[\/pb_glossary]<\/strong> breaks lactose into glucose and galactose. Only fibers remain to move into the large intestine. Fibers attract water which softens stool. Some bacteria ferment some fibers, releasing water, gas, and short-chain fatty acids. The liver can change glycogen to glucose to increase blood glucose levels or convert glucose to glycogen to decrease blood glucose. The liver also converts other non-carbohydrates into glucose when needed.\r\n\r\n \r\n\r\n[pb_glossary id=\"253\"]Simple sugars[\/pb_glossary]<\/strong> exist in equilibrium between their ring structure form and their straight chain form. Solutions of monosaccharides and certain disaccharides, such as maltose and lactose, contain [pb_glossary id=\"254\"]free aldehyde[\/pb_glossary]<\/strong> functional groups. The term 'free' means that the aldehyde is exposed at the end of the straight chain form rather than being bonded to other parts of the molecule on both ends in ring form. The free aldehyde functional group can [pb_glossary id=\"259\"]reduce[\/pb_glossary]<\/strong> other molecules by donating an electron to another molecule via loss of a hydrogen. Due to this ability, simple sugars are calked [pb_glossary id=\"256\"]reducing sugars[\/pb_glossary]<\/strong>. One of the molecules that can be reduced by the free aldehyde is Benedict's solution. When the [pb_glossary id=\"255\"]Benedict's solution[\/pb_glossary]<\/strong> is reduced, it changes color. A very small amount of reducing sugar will turn the Benedict's solution a greenish yellow; greater amounts of reducing sugar will be indicated by color changes from yellow through orange to brick red. A rust color indicates that a large number of reducing sugars are present.\r\n\r\nBoth starch and cellulose are polysaccharide carbohydrates composed of many subunits of the monosaccharide glucose joined in long chains. However, the orientation of the bond between the glucose monomers is different in the two polysaccharides. Cellulose bonds are oriented so that the bonds are resistant to human digestive enzymes. Starch bonds are oriented so that human digestive enzymes can hydrolyze the bond and break down the starch molecule. The bond orientation in starch also causes starch to react with [pb_glossary id=\"257\"]iodine[\/pb_glossary]<\/strong> solution to display a dark blue\/black color.\r\n
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Key Terms<\/h4>\r\n<\/header>\r\n
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