Lab Report: #1 Identifying Carbohydrates
To determine whether a substance contains reducing sugars and/or polysaccharides (two types of carbohydrates) by using Benedict's reagent and iodine stain.
Carbohydrates are essential to living organisms, and the principal role of carbohydrates is the production of energy. Carbohydrates are groups of sugars that contain carbon, oxygen, and hydrogen in a 1:2:1 ratio. Three main units of carbohydrates are monosaccharides, disaccharides, and polysaccharides.
A monsaccharide contains one sugar unit, and has three to seven carbon atoms. Monosaccharides have a hydroxyl group bonded to each carbon atom; expect one, which is bonded to an oxygen atom thus forming a carbonyl group. If the carbonyl group is at the end of the chain then is it an aldehyde; therefore, if it is located in any other position it is a ketone. Common monosaccharides are ribose, deoxyribose, glucose, fructose, and galatose.
Two monosaccharides can be joined by dehydration synthesis to form a disaccharide. The hydroxide ions on carbon-1 of one molecule and the hydroxide ions on carbon-4 of another molecule give up two hydrogen atoms and one oxygen atom to form water, and then are joined together by the remaining oxygen atom. Common disaccharides are maltose, sucrose, and lactose.
Polysaccharides are the most abundant carbohydrate in the biosphere. Polysaccharides are long chains of monosaccharides, usually glucose, that are all hooked together by 1-4 glycosidic linkages formed through dehydration synthesis. There are two main categories of polysaccharides, storage polysaccharides and structural polysaccharides. Storage polysaccharides include starches and glycogen. The starches are bonded by carbon 1 of one glucose is linked to carbon 4 of the next glucose. Structural polysaccharides include cellulose. Cellulose is found in plant cell walls and is the most abundant organic compoun