The process by which green plants make their own food by using sunlight, water and carbon dioxide is called photosynthesis.

Photosynthesis:

Photosynthesis is a vital biological process that occurs in plants, algae, and some bacteria. It is the process by which organisms convert light energy from the sun into chemical energy in the form of glucose (a sugar molecule), while also releasing oxygen. This process plays a crucial role in maintaining the balance of oxygen and carbon dioxide in the atmosphere, as well as providing a source of energy for living organisms.

Process of Photosynthesis:

Photosynthesis can be divided into two stages: the light-dependent reactions and the light-independent reactions.

1. Light-Dependent Reactions:
- Takes place in the thylakoid membranes of chloroplasts.
- It requires light energy to occur.
- Chlorophyll, a pigment present in chloroplasts, absorbs light energy from the sun.
- This energy is used to split water molecules into oxygen, hydrogen ions, and electrons.
- The released oxygen is released into the atmosphere.
- The electrons and hydrogen ions are used in the next stage.

2. Light-Independent Reactions (Calvin Cycle):
- Takes place in the stroma of chloroplasts.
- It does not require direct light energy.
- The electrons and hydrogen ions obtained from the light-dependent reactions are used to convert carbon dioxide into glucose.
- This process is called carbon fixation.
- The glucose produced is used by plants as a source of energy for growth and reproduction.

Importance of Photosynthesis:

Photosynthesis is a vital process for several reasons:

1. Oxygen Production:
- Photosynthesis is responsible for the production of oxygen, which is essential for the survival of living organisms.
- Plants release oxygen into the atmosphere as a byproduct of photosynthesis, allowing animals and humans to breathe.

2. Carbon Dioxide Absorption:
- Photosynthesis helps in reducing the amount of carbon dioxide in the atmosphere.
- Carbon dioxide is a greenhouse gas that contributes to global warming, and plants absorb it during photosynthesis.

3. Energy Source:
- The glucose produced during photosynthesis serves as a primary source of energy for plants, which is used for growth, reproduction, and metabolism.
- Other organisms, including humans, indirectly rely on this energy by consuming plants or plant-eating animals.

4. Food Production:
- Photosynthesis is the basis for food production in plants, which is essential for sustaining life on Earth.
- Through photosynthesis, plants convert sunlight, water, and carbon dioxide into glucose, which is used to produce fruits, vegetables, grains, and other plant-based food sources.

In conclusion, photosynthesis is a complex process that converts light energy into chemical energy, producing glucose and oxygen. It plays a critical role in maintaining the balance of atmospheric gases, providing energy, and supporting food production in the natural world.