2). How are simple carbohydrates, like glucose, used to build starches?

Carbohydrates which include sugars and starches are the primary energy sources produced in plants and used by heterotrophic organisms.

Carbohydrates are composed of a basic chemical formula that typically contains a ratio of one Carbon atom for every two Hydrogen atoms and one Oxygen atom C1H2O1. Basically one carbon atom for every one water molecule Carbon + Water = Carbohydrate.

Monosaccharides or Single Carbon Chain Sugars include Glucose C6H12O6

Disaccharides or Double Carbon Chain Sugars include Sucrose C12H22O11

Combining monosaccharides and disaccharides create Polysaccharides which are complex sugars called starches.