Organic Chemistry MCAT Practice Exam

What type of bond connects two sugars in a glycosidic linkage?

1. Amide bond

2. Glycogen bond

3. Acetal bond

4. Peptide bond

The correct answer is: Acetal bond

In a glycosidic linkage, the type of bond that connects two sugar molecules is indeed an acetal bond. When two monosaccharides join together to form a disaccharide, a condensation reaction occurs where a water molecule is released and a glycosidic bond is formed between the anomeric carbon of one sugar and a hydroxyl group of the other sugar. This bond can be viewed as a specific type of acetal formation, where the hydroxyl group forms an ether linkage, thereby creating a new acetal functional group between the two sugar units. The significance of the acetal bond in glycosidic linkage allows sugar molecules to form larger carbohydrate structures, including polysaccharides. This not only contributes to the formation of important biomolecules like starch and cellulose but also illustrates the versatility of sugar chemistry in biological systems. Understanding this reaction and the nature of the bond is crucial for grasping the biochemical pathways involving carbohydrates, their storage, and energy release in living organisms.