Organic Chemistry MCAT Practice Exam

How does branching in glycogen occur?

1. Through beta-1,4-glycosidic bonds

2. Through alpha-1,6-glycosidic bonds

3. Through delta-1,6-glycosidic bonds

4. Through alpha-1,2-glycosidic bonds

The correct answer is: Through alpha-1,6-glycosidic bonds

Branching in glycogen occurs through alpha-1,6-glycosidic bonds. Glycogen is a highly branched polymer of glucose that serves as a key energy storage molecule in animals. The structure of glycogen consists of long chains of glucose units connected primarily by alpha-1,4-glycosidic bonds, which form the linear portions of the molecule. However, to create branches, glycogen utilizes alpha-1,6-glycosidic bonds. These bonds are formed when a glucose unit is linked to one of the existing chains at a position where it creates a side branch, resulting in a more compact and efficient structure for energy storage. The presence of these branches allows for rapid access to glucose units when energy is needed by the body, as enzymes can act on multiple non-reducing ends. This characteristic makes glycogen an effective energy reservoir in the liver and muscles, facilitating quick mobilization of glucose during periods of high energy demand.