Carbohydrates are important in cells as a useable energy source and form important parts of the cell wall in plants. Common carbohydrates are sugars and starch. The basic structure of all carbohydrates is the same. They are all made up of carbon and hydrogen.
Monosaccharides & Disaccharide's
"Know the difference between monosaccharides, disaccharides and polysaccharides"
Monosaccharides are sometimes referred to as simple sugars. They have the general formula (CH2O)n where n can be any number but is usually low.
Disaccharides are made up of two monosaccharides joined together by a glycosidic bond in a condensation reaction. These are sometimes referred to as the double sugars and have the general formula (C6H10O5)n
Hexose, Glucose & Pentose Ribose Structure
"Know the structure of the hexose glucose (alpha & beta) and the pentose ribose"
Glucose comes in two different forms known as alpha-glucose and beta-glucose. These two isomers are caused by the different arrangements of the atoms on the side chains of the molecule. The change is only very subtle but gives the molecules very different properties. For the exam it is important to know the exact structures of the molecules and the differences between each.
Formation & Properties of Disaccharides and Polysaccharides
"Understand how monosaccharides (glucose, fructose, galactose) join to form the disaccharides (sucrose, lactose, maltose) and the polysaccharides (starch formed from amylose and amylopectin; glycogen) through condensation reactions forming glycosidic bonds and how these can be split through hydrolysis reactions."
Disaccharides are formed when two monosaccharides join together in a condensation reaction to form a glycosidic bond. A condensation reaction involves the elimination of one molecule of H2O.
The use of numbers shows us which carbon atoms are involved in the glycosidic bond. eg: 1,4-glycosidic bond.
The following table shows us which monosaccharides join together to form each disaccharide: