Monosaccharides containg an aldehyde group are called aldoses while those containing a keto group are called ketoses. The aldehyde group is usually present at `C_1` while the keto group is usually present at `C_2`. All monosaccharides containing five ans six carbon atoms have cyclic structures , furanose (five membered) and pyranose (six membered). During ring formation. `C_1` in aldoses and `C_2` in ketoses becomes chiral and hence all these monosaccharides exist in two steroismeric forms called the `alpha`-anomer and the `beta`-anomer while `C_1` and `C_2` are called glycosidic or anomeric carbon atoms. In contrast, steroisomers , which differ in configuration at any other chiral carbon other than the glycosidic carbon are called epimers. Two molecules of the same or different monosaccharides combine together through glycosidic linkage to form dissacharides. All monosaccharides (aldoses and ketoses) and disacchardies expect sucrose reduce Tollens' reagent and Fehling's solution , undergo mutarotation and form osazones.
In disaccharides , the linkage connecting monosaccharide units is called.

Options

A. glycoside linkage
B. nuclesoside linkage
C. glycogen linkage
D. peptide linkage.

Answer

To answer the question regarding the linkage connecting monosaccharide units in disaccharides, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Monosaccharides**: Begin by recognizing that monosaccharides are the simplest form of carbohydrates, consisting of single sugar units. They can be classified as aldoses (containing an aldehyde group) or ketoses (containing a keto group).

2. **Formation of Disaccharides**: Disaccharides are formed when two monosaccharides combine. This occurs through a chemical reaction where the hydroxyl (OH) group of one monosaccharide reacts with the hydroxyl group of another monosaccharide.

3. **Glycosidic Linkage**: The specific type of bond that forms between the two monosaccharides during this reaction is known as a glycosidic linkage. This linkage is formed when a water molecule is removed (a dehydration synthesis reaction), resulting in a covalent bond between the two sugar units.

4. **Example of Disaccharides**: For instance, when two glucose molecules combine, they form maltose through a glycosidic linkage. The linkage can be designated as α(1→4) or β(1→4) depending on the orientation of the hydroxyl group on the anomeric carbon.

5. **Conclusion**: Therefore, the linkage connecting monosaccharide units in disaccharides is called a glycosidic linkage.

### Final Answer:
The linkage connecting monosaccharide units in disaccharides is called a **glycosidic linkage**.

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