How do plants store excess glucose?

Plants store excess glucose as starch in their cells.

Plants, like all living organisms, need energy to survive and grow. They obtain this energy through the process of photosynthesis, where they convert sunlight, carbon dioxide and water into glucose and oxygen. Glucose is a simple sugar that provides immediate energy for the plant's metabolic processes. However, not all the glucose produced is used straight away. Some of it is converted into a more complex carbohydrate called starch and stored for later use.

Starch is a polysaccharide, a large molecule made up of many glucose units linked together. It is insoluble in water, which makes it an ideal storage compound. If glucose, which is soluble, was stored directly, it would cause the plant cells to take in water by osmosis and potentially burst. By converting glucose to starch, plants avoid this problem.

The process of converting glucose to starch takes place in the chloroplasts, the same organelles where photosynthesis occurs. The glucose molecules are joined together by a series of enzymes, forming long chains that twist into a helix shape. This compact structure allows a large amount of glucose to be stored in a small space.

When the plant needs energy, for example during the night when photosynthesis cannot occur, it breaks down the stored starch back into glucose. This glucose is then used in cellular respiration to produce ATP, the energy currency of the cell. This process ensures that the plant has a constant supply of energy, even when conditions for photosynthesis are not ideal.

In summary, plants store excess glucose as starch, a complex carbohydrate that is insoluble in water. This process allows plants to maintain a steady supply of energy, even when they are not actively photosynthesising.