What do chloroplasts primarily do in plant cells?

Chloroplasts are essential organelles found in plant cells that primarily function in the process of photosynthesis. During this process, chloroplasts absorb light energy from the sun, which is then converted into chemical energy stored in the form of high-energy molecules, primarily glucose. This transformation occurs through two main stages: the light-dependent reactions and the light-independent reactions (Calvin cycle). In the light-dependent reactions, chlorophyll and other pigments capture light energy, which is then used to generate ATP and NADPH. These high-energy molecules are essential for the synthesis of glucose during the Calvin cycle, where carbon dioxide is fixed and converted into carbohydrate using the energy stored in ATP and NADPH.

The other options refer to functions not associated with chloroplasts. Storing genetic information is primarily the role of the cell nucleus, while regulating water balance is generally handled by the vacuole and various transport proteins in the cell membrane. Lastly, the transport of proteins across membranes involves specific cellular mechanisms such as vesicles or channels, which are not functions of chloroplasts.