Which statementsare correct?

Options

A. Lactose is a disaccharide and is a reducing sugar.
B. `alpha`-D-glucopyranoside and `beta` - D-glucopyranose are anomers.
C. Methyl `-alpha`-D-glucopyranoside has an acetal structure and is a non-reducing sugar.
D. `alpha`-D-Glucopyranose has a hemiacetal structure and is a reducing sugar.

Answer

To determine which statements are correct regarding the biomolecules, we will analyze each statement step by step.

### Step 1: Analyze the first statement
**Statement:** Lactose is a disaccharide and is a reducing sugar.

- **Explanation:** Lactose is indeed a disaccharide composed of two monosaccharides: glucose and galactose. A reducing sugar is defined as a sugar that can be oxidized and can reduce other compounds. To confirm if lactose is a reducing sugar, we can perform tests using Tollen's reagent and Benedict's reagent (also known as the celling reagent). Lactose can reduce these reagents, indicating that it is a reducing sugar. Therefore, this statement is correct.

### Step 2: Analyze the second statement
**Statement:** Alpha-D-glucopyranoside and beta-D-glucopyranoside are anomers.

- **Explanation:** Anomers are a type of stereoisomer that differ in configuration at the anomeric carbon (the carbon that is derived from the carbonyl carbon during the formation of the cyclic structure). In the case of D-glucose, the alpha form has the hydroxyl group (OH) on the anomeric carbon below the plane of the ring, while in the beta form, the hydroxyl group is above the plane. Since these two forms differ only in the position of the OH group at the anomeric carbon, they are indeed anomers. Therefore, this statement is also correct.

### Step 3: Analyze the third statement
**Statement:** Methyl-D-glucopyranoside has an acetyl structure and is a non-reducing sugar.

- **Explanation:** Methyl-D-glucopyranoside is a derivative of glucose where the hydroxyl group at the anomeric carbon is replaced with a methoxy group (–OCH3). This modification prevents the sugar from participating in redox reactions, making it a non-reducing sugar. Additionally, any sugar that has an acetyl structure (which is a type of ether) is also non-reducing. Therefore, this statement is correct.

### Conclusion
After analyzing all three statements, we can conclude that:
- All statements are correct.