Question

Explain the mechanism of photosynthesis.

Answer 1

Photosynthesis:

1. 'Photo' means ‘light’ and ‘synthesis’ means ‘making something’.
2. Photosynthesis is the process by which green plants make their food in presence of sunlight.
3. Through this process, light energy is converted into chemical energy.
4. During photosynthesis, carbon dioxide and water are utilized to form carbohydrates.
5. Oxygen is liberated as a by-product after photosynthesis.

Site of photosynthesis:

1. The leaves of plants contain some small cellular organelles called chloroplasts.
2. Chloroplasts are present only within the mesophyll cells of plant leaves.
3. Chloroplasts are the sites of photosynthesis.
4. Each chloroplast contains a green-colored pigment called chlorophyll.
5. So, all green parts of the plant can execute photosynthesis.

Steps of photosynthesis:

1. During photosynthesis, light energy from the sun is absorbed by chlorophyll.
2. Water from the soil is absorbed by the root hairs and is carried to the leaves.
3. Carbon dioxide from the air enters through the stomata of the leaves.
4. In the meantime, water molecules are split into hydrogen and oxygen.
5. This hydrogen and carbon dioxide then combine to form carbohydrates (glucose).
6. Glucose is the source of energy that provides growth and development.
7. Later, it is converted into starch and is stored in different plant organs.

Types of photosynthesis:

• Oxygenic photosynthesis:

1. It is more common.
2. Plants, algae, and cyanobacteria execute oxygenic photosynthesis.
3. In this type, electrons are transferred from water to carbon dioxide by light energy.
4. Carbon dioxide is taken and oxygen is expelled in this process.

• Anoxygenic photosynthesis:

1. Certain bacteria (green sulphur bacteria, purple bacteria) execute this type of photosynthesis.
2. Oxygen is not produced.

Significance of photosynthesis:

1. Maintains oxygen balance in the atmosphere.
2. Provides nutrients to the plants.
3. It is a great energy reserve.