Thus animals store surplus carbohydrate as glycogen; plants do so in form of starch. Starch is producing in the stroma of chloroplasts and stored there as starch grains. The Starch synthesis happens from CDP- glucose, ADP-glucose or GDP-glucose (but not UDP-glucose).  The pathway contain the conversion of glyceraldehyde 3-phosphate (from the Calvin cycle) to glucose 1-phosphate that in turn is used to synthesize the nucleotide sugar derivatives.