Question

Which one of the following compounds contains \(\beta\)-C\(_1\)-C\(_4\) glycosidic linkage?

• A. Lactose
• B. Amylose
• C. Sucrose
• D. Maltose

Hint:

Milk sugar (Lactose) is unique among common dietary disaccharides for having a \(\beta\)-linkage that requires the specific enzyme lactase for digestion.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Glycosidic linkages are the oxygen bridges connecting monosaccharide units in disaccharides or polysaccharides. The \(\alpha\) or \(\beta\) prefix refers to the stereochemistry at the anomeric carbon (C\(_1\)).
Step 2: Detailed Explanation:
- Lactose: Composed of \(\beta\)-D-galactose and \(\beta\)-D-glucose. The linkage is between C\(_1\) of galactose and C\(_4\) of glucose in a \(\beta\) configuration (\(\beta\)-1,4-linkage).
- Amylose: A linear polymer of \(\alpha\)-D-glucose units joined by C\(_1\)-C\(_4\) glycosidic linkages in an \(\alpha\) configuration.
- Sucrose: Composed of \(\alpha\)-D-glucose and \(\beta\)-D-fructose joined by a glycosidic linkage between C\(_1\) of glucose and C\(_2\) of fructose (\(\alpha\)-1,2-linkage).
- Maltose: Composed of two \(\alpha\)-D-glucose units joined by a C\(_1\)-C\(_4\) glycosidic linkage in an \(\alpha\) configuration.
Step 3: Final Answer:
Only lactose contains the \(\beta\)-C\(_1\)-C\(_4\) glycosidic linkage.