The macromolecule class of carbohydrates includes the extensive group of sugars and polymers of sugars. Monosaccharides are the monomers of carbohydrates that, joined together through a dehydration reaction and a covalent bond, form polysaccharides. The bond between carbohydrates is called a glycosidic linkage. When only two monosaccharides are joined together, the product is a disaccharide.
Some common examples of disaccharides include maltose, sucrose, and lactose (sugars generally end in “ose”). Maltose is composed of two glucose molecules bonded to each other. This disaccharide is commonly used in brewing beer. The way each molecule bonds is very specific to each disaccharide. In maltose, the number 1 carbon of one glucose bonds to the number 4 carbon of the other glucose. If the glucose molecules were bonded in a different, the resulting disaccharid would also have been different. One of the most common disaccharides is sucrose, a.k.a. table sugar. Sucrose is made of glucose and fructose bonded together by glycosidic links. In sucrose, the number 1 carbon in glucose bonds to the number 2 carbon in fructose. The disaccharide shown in the picture (or attempted to show..) is lactose. Lactose is the sugar naturally found in milk, unless, like the milk shown in the photo, it has been removed for health reasons. Lactose is composed of a glucose molecule joined to a galactose molecule by a glycosidic link. Because many people do not have the enzyme (lactase) necessary to break down lactose (this is known as lactose intolerance), different types of milk have been made to cater to these needs. This milk, for example, has added lactase, the enzyme used to break down lactose (enzymes generally end in “ase”). Other options include milk made from sources other than animals, such as almond milk, rice milk, and coconut milk.