Read an Academic Passage

The Vital Process of Photosynthesis

Photosynthesis is the fundamental biological process by which green plants, algae, and some bacteria convert light energy into chemical energy. This process is essential for nearly all life on Earth, as it produces the oxygen we breathe and the energy that fuels most ecosystems. The overall chemical reaction involves taking in carbon dioxide from the atmosphere and water from the soil. Using energy from sunlight, these raw materials are transformed into glucose, a type of sugar that stores energy for the plant, and oxygen, which is released as a byproduct. This remarkable conversion takes place within specialized organelles called chloroplasts.

The process of photosynthesis is typically divided into two main stages: the light-dependent reactions and the light-independent reactions (also known as the Calvin cycle). The light-dependent reactions occur in the thylakoid membranes of the chloroplasts and, as the name suggests, require sunlight. During this stage, light energy is captured by chlorophyll, a green pigment, and used to split water molecules. This reaction releases oxygen and creates energy-carrying molecules. These molecules, ATP and NADPH, are then used to power the next stage of the process.

The light-independent reactions take place in the stroma of the chloroplasts and do not directly require light. In this stage, the chemical energy captured during the light-dependent reactions is used to convert carbon dioxide into glucose. This cycle of reactions effectively "fixes" carbon from the air into an organic molecule that the plant can use for growth and metabolism. This stored energy is then passed through the food chain as animals eat plants, making photosynthesis the ultimate source of energy for most living organisms.