disaccharide

Examples of disaccharide in the following topics:

• Carbohydrate Molecules

  • Carbohydrates are classified into three subtypes: monosaccharides, disaccharides, and polysaccharides.
  • Common disaccharides include lactose, maltose, and sucrose.
  • Lactose is a disaccharide consisting of the monomers glucose and galactose.
  • Maltose, or malt sugar, is a disaccharide formed by a dehydration reaction between two glucose molecules.
  • The most common disaccharide is sucrose, or table sugar, which is composed of the monomers glucose and fructose.

• Types of Biological Macromolecules

  • Regular table sugar is the disaccharide sucrose (a polymer), which is composed of the monosaccharides fructose and glucose (which are monomers).
  • The carbohydrate monosaccharides (fructose and glucose) are joined to make the disaccharide sucrose.

• Importance of Carbohydrates

  • One major class of biological macromolecules are carbohydrates, which are further divided into three subtypes: monosaccharides, disaccharides, and polysaccharides .
  • Carbohydrates are biological macromolecules that are further divided into three subtypes: monosaccharides, disaccharides, and polysaccharides.

• Digestion and Absorption

  • The salivary enzyme amylase begins the breakdown of food starches into maltose, a disaccharide.
  • Pancreatic juices also contain amylase, which continues the breakdown of starch and glycogen into maltose and other disaccharides.
  • These disaccharides are then broken down into monosaccharides by enzymes called maltases, sucrases, and lactases.

• Hydrolysis

  • In the hydrolysis reaction shown here, the disaccharide maltose is broken down to form two glucose monomers with the addition of a water molecule.

• Connecting Other Sugars to Glucose Metabolism

  • Sucrose is a disaccharide with a molecule of glucose and a molecule of fructose bonded together with a glycosidic linkage.

• The lac Operon: An Inducer Operon

  • The lac operon encodes the genes necessary to acquire and process the lactose from the local environment, which includes the structural genes lacZ, lacY, and lacA. lacZ encodes β-galactosidase (LacZ), an intracellular enzyme that cleaves the disaccharide lactose into glucose and galactose. lacY encodes β-galactoside permease (LacY), a membrane-bound transport protein that pumps lactose into the cell. lacA encodes β-galactoside transacetylase (LacA), an enzyme that transfers an acetyl group from acetyl-CoA to β-galactosides.

• Digestive System: Mouth and Stomach

  • In addition, saliva contains an enzyme called salivary amylase that begins the process of converting starches in the food into a disaccharide called maltose.