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🥼organic chemistry review

α(1→4) Glycosidic Bond

Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025

Definition

The α(1→4) glycosidic bond is a type of covalent bond that connects two monosaccharide units, forming a disaccharide. This specific bond is found in important disaccharides like sucrose and starch, and it plays a crucial role in the structure and function of these carbohydrates.

5 Must Know Facts For Your Next Test

  1. The α(1→4) glycosidic bond is formed between the anomeric carbon (C1) of one monosaccharide and the hydroxyl group (OH) on the fourth carbon (C4) of another monosaccharide.
  2. This bond is found in the disaccharides sucrose (glucose and fructose) and maltose (two glucose units), as well as in the polysaccharide starch.
  3. The α configuration of the glycosidic bond means that the hydroxyl group on the anomeric carbon is in the axial position, which is important for the structural and functional properties of the disaccharide.
  4. The (1→4) linkage refers to the position of the glycosidic bond, where the first carbon of one monosaccharide is connected to the fourth carbon of the adjacent monosaccharide.
  5. The α(1→4) glycosidic bond is resistant to hydrolysis by human digestive enzymes, which is why starch, a polymer of α(1→4)-linked glucose units, is a source of complex carbohydrates in the human diet.

Review Questions

  • Explain the significance of the α(1→4) configuration in the glycosidic bond and how it affects the structure and function of disaccharides.
    • The α(1→4) configuration of the glycosidic bond means that the hydroxyl group on the anomeric carbon (C1) of one monosaccharide is in the axial position relative to the adjacent monosaccharide. This specific orientation is crucial for the structural and functional properties of disaccharides like sucrose and maltose. The α(1→4) bond allows for the formation of linear, helical structures, which is important for the storage and digestion of carbohydrates. Additionally, the α(1→4) linkage makes the bond resistant to hydrolysis by human digestive enzymes, allowing for the slow release of glucose from complex carbohydrates like starch.
  • Describe the role of the α(1→4) glycosidic bond in the structure and function of the disaccharide sucrose.
    • Sucrose, a disaccharide composed of glucose and fructose, is connected by an α(1→4) glycosidic bond. This specific bond orientation allows sucrose to adopt a linear structure, which is important for its storage and transport functions in plants. The α(1→4) linkage also makes sucrose resistant to hydrolysis by human digestive enzymes, meaning that it is broken down more slowly than other disaccharides. This slow release of glucose and fructose from sucrose helps to regulate blood sugar levels and provides a steady supply of energy to the body.
  • Analyze the relationship between the α(1→4) glycosidic bond and the structure and digestibility of the polysaccharide starch.
    • Starch, a polysaccharide composed of long chains of α(1→4)-linked glucose units, is an important source of complex carbohydrates in the human diet. The α(1→4) glycosidic bond allows starch to form a helical, crystalline structure that is resistant to hydrolysis by human digestive enzymes. This resistance to digestion means that starch is broken down more slowly, providing a sustained release of glucose into the bloodstream. The α(1→4) linkage is crucial for the storage and mobilization of glucose in plants, as well as the slow digestion and absorption of starch in the human body, which helps to regulate blood sugar levels and provide a steady supply of energy.