Textbook Question
Isomaltose, obtained from the breakdown of starch, has the following Haworth structure:
b. What are the monosaccharides in isomaltose?
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20. Carbohydrates
Disaccharides
1:51 minutesProblem 76
Textbook Question
The disaccharide trehalose found in mushrooms is composed of two α-D-glucose molecules joined by an α(1→1)−glycosidic bond. Draw the Haworth structure for trehalose.
Verified step by step guidance1
Understand the structure of α-D-glucose: Begin by recalling the Haworth structure of α-D-glucose. It is a six-membered ring (pyranose form) with the hydroxyl group (-OH) on carbon-1 pointing downward (α-anomer).
Identify the glycosidic bond: The problem states that the two α-D-glucose molecules are joined by an α(1→1)-glycosidic bond. This means the bond is formed between the anomeric carbons (carbon-1) of both glucose molecules, with the oxygen atom acting as the bridge.
Draw the first glucose molecule: Start by sketching the Haworth structure of the first α-D-glucose molecule. Label the carbons (1 through 6) and ensure the -OH group on carbon-1 is pointing downward.
Connect the second glucose molecule: Draw the second α-D-glucose molecule in its Haworth form. Rotate it slightly so that its carbon-1 aligns with the carbon-1 of the first glucose. Use an oxygen atom to connect the two carbon-1 atoms, forming the α(1→1)-glycosidic bond.
Complete the structure: Ensure all other hydroxyl groups (-OH) and hydrogen atoms are correctly positioned on the glucose rings. Verify that the glycosidic bond is labeled as α(1→1) and that the overall structure represents trehalose.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Disaccharides
Disaccharides are carbohydrates formed by the condensation of two monosaccharides, resulting in a glycosidic bond. In the case of trehalose, it consists of two α-d-glucose units linked together. Understanding disaccharides is essential for grasping how they function in biological systems and their structural properties.
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Glycosidic Bonds
A glycosidic bond is a type of covalent bond that connects a carbohydrate molecule to another group, which can be another carbohydrate. The specific type of glycosidic bond in trehalose is α(1→1), indicating the orientation and position of the bond between the glucose units. This bond is crucial for determining the properties and digestibility of the sugar.
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Haworth Structure
The Haworth structure is a way of representing the cyclic form of carbohydrates, showing the arrangement of atoms in a ring. For trehalose, drawing its Haworth structure involves illustrating the two glucose units in their cyclic forms, including the anomeric carbons and the orientation of hydroxyl groups. This representation is vital for understanding the molecule's chemical behavior and interactions.
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