What is the primary function of chloroplasts in plant cells?

Chloroplasts are specialized organelles found in plant cells that play a critical role in the process of photosynthesis. This is the mechanism by which plants, along with some algae and bacteria, convert light energy, usually from the sun, into chemical energy stored in glucose, a sugar. The chloroplasts contain chlorophyll, the green pigment that captures light energy and facilitates the transformation of carbon dioxide and water into glucose and oxygen.

During photosynthesis, chloroplasts engage in two main stages: the light-dependent reactions, which occur in the thylakoid membranes, and the light-independent reactions, or Calvin cycle, which occur in the stroma. In the light-dependent reactions, sunlight is converted into energy-rich compounds, such as ATP and NADPH, which are then used in the Calvin cycle to produce glucose.

The primary function of chloroplasts is therefore essential for the survival of plants and forms the base of the food chain, directly linking them to the energy needs of almost all other living organisms on Earth. This process not only sustains the plant itself but also produces oxygen as a byproduct, contributing significantly to the planet's atmosphere.