Which of the following sugars are reducing sugars? Which ones would undergo mutarotation?
(c) 6-O-(β-D-galactopyranosyl)-D-glucopyranose

검증된 단계별 안내

Step 1: Understand the structure of the given sugar, 6-O-(β-D-galactopyranosyl)-D-glucopyranose. This is a disaccharide where a β-D-galactopyranose unit is linked to a D-glucopyranose unit through an oxygen atom at the 6th position of the glucose ring.

Step 2: Recall the definition of a reducing sugar. A sugar is considered reducing if it has a free anomeric carbon (a carbon attached to a hydroxyl group and double-bonded to an oxygen atom) that can open up to form an aldehyde or ketone group in solution.

Step 3: Analyze the structure to determine if either of the two sugar units has a free anomeric carbon. In this case, the anomeric carbon of the β-D-galactopyranose is involved in the glycosidic bond, so it is not free. However, the anomeric carbon of the D-glucopyranose is free, making this sugar a reducing sugar.

Step 4: Recall the concept of mutarotation. Mutarotation occurs when a sugar with a free anomeric carbon interconverts between its α and β anomers in solution. Since the D-glucopyranose unit has a free anomeric carbon, it can undergo mutarotation.

Step 5: Conclude that 6-O-(β-D-galactopyranosyl)-D-glucopyranose is a reducing sugar because it has a free anomeric carbon on the D-glucopyranose unit, and it can undergo mutarotation for the same reason.

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11m

주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Reducing Sugars

Reducing sugars are carbohydrates that can donate electrons to other molecules, typically due to the presence of a free aldehyde or ketone group. Common examples include glucose and fructose. These sugars can reduce metal ions, which is a key characteristic used in various biochemical tests.

Mutarotation

Mutarotation is the change in optical rotation that occurs when an anomeric carbon in a sugar ring opens and closes, interconverting between its alpha and beta forms. This process is significant in sugars like glucose and galactose, where the anomeric carbon can exist in two different configurations, affecting their reactivity and properties.

Glycosidic Bonds

Glycosidic bonds are covalent linkages formed between the anomeric carbon of a sugar and another molecule, which can be another sugar or a different type of compound. In the case of disaccharides or oligosaccharides, the presence of a glycosidic bond can prevent mutarotation and the reducing ability of the sugar, as it locks the anomeric carbon in a specific configuration.

Which of the following sugars are reducing sugars? Which ones would undergo mutarotation?(c) 6-O-(β-D-galactopyranosyl)-D-glucopyranose