Disakarida
Disakarida, also known as disaccharide, is a carbohydrate composed of two monosaccharide units linked by a glycosidic bond. They are typically formed by a dehydration reaction, in which a molecule of water is removed as the bond forms. The two monosaccharide units may be identical (homodisaccharides) such as maltose and trehalose, or different (heterodisaccharides) such as sucrose and lactose. The glycosidic linkage is described by the carbon atoms involved and the anomeric configuration (for example, alpha-1→4 or beta-1→4). Depending on the linkage, many disaccharides are reducing, meaning they can open to reveal a free aldehyde or ketone on a monosaccharide; others are non-reducing, such as sucrose, where both anomeric carbons participate in the bond and cannot open to form a reducing end.
- Sucrose: glucose and fructose linked by an alpha-1→2 bond; non-reducing, widely used as table sugar.
- Lactose: galactose and glucose linked by a beta-1→4 bond; reducing.
- Maltose: two glucose units linked by an alpha-1→4 bond; reducing.
- Trehalose: two glucose units linked by an alpha-1→1 bond; non-reducing.
Biological role and metabolism: disaccharides provide a rapid source of energy in the diet. They are hydrolyzed
Occurrence and uses: they occur in foods from plant and animal sources (sucrose in cane and beet;