Which molecule donates activated glucose units during glycogen synthesis?

### Why this is right Glycogen synthase transfers glucose from UDP-glucose to a glycogen chain, releasing uridine diphosphate. UDP-glucose is the activated glucose donor used in glycogen synthesis. ### The concept Glucose is first converted to glucose-1-phosphate, which reacts with uridine triphosphate to produce UDP-glucose. The activated sugar is then incorporated into glycogen. ### The other options - **Glucose-6-phosphate**: It is an intermediate that can be converted to glucose-1-phosphate, but it is not the direct donor to glycogen synthase. - **ATP**: It supplies energy in other reactions but does not donate glucose units. - **Fructose-1,6-bisphosphate**: This is a glycolytic intermediate, not a glycogen precursor donor. ### Terms - **UDP-glucose**: Activated glucose linked to uridine diphosphate. - **Glycogen synthase**: The enzyme that lengthens glycogen chains. ### Remember Glycogen synthase uses activated UDP-glucose, not free glucose.