Plants do not store carbohydrate as glucose but do so as starch because glucose?

Answer 1

Glucose formed during photosynthesis is used as a short-term energy source in plants. However, as glucose is water-soluble, it cannot be used for long-term storage of energy. The glucose molecules are bonded together to form long-chains of insoluble starch molecules, which are more readily stored in cell amyloplasts and cannot be leached from the cell by water

Starch, being insoluble in water, does not affect the movement of solutes within cells. If energy was stored in the form of glucose, the solute concentration in cell cytoplasm would fluctuate wildly resulting in changes in water movement which the cell would be unable to withstand. Metabolic utilisation would then be seriously compromised.

Starch molecules, whether in the form of amylose or amylopectin, are too large to move out of the amyloplasts, unlike glucose, which readily moves between cells and is therefore of little use for long-term storage of energy.

Hydrolysis of starch into glucose is readily accomplished when necessary. In plants, the hydrolysis occurs within the cells. In animals, enzymes hydrolyse the starch of plant material into sugars.

There are a number of more complex reasons as well but I think the above should be enough for your homework!