How is glycogen formed?

• A. By breaking down glucose to produce energy
• B. By converting glycogen into amino acids
• C. By oxidizing glucose to carbon dioxide
• D. By linking together large numbers of glucose molecules

Answer: (D)

Glycogen is formed by assembling glucose units into a branched polymer, a process called glycogenesis. Glucose is activated to UDP-glucose and then glycogen synthase adds these glucose units to a growing chain, creating mainly alpha-1,4 bonds, with branching enzyme forming alpha-1,6 linkages to produce a highly branched molecule. This structure stores glucose for quick release when energy is needed, especially in liver and muscle. The other ideas describe breaking down glucose to release energy, converting glycogen to amino acids, or oxidizing glucose to CO2—none of which describe forming glycogen. So linking together large numbers of glucose molecules is how glycogen is formed.