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How do plants make their food by photosynthesis?

Class 10 ScienceNCERT chapter: Life Processesइसे हिंदी में पढ़ें

Exam-ready answer

Photosynthesis is the process by which green plants make food. In the presence of sunlight, chlorophyll in chloroplasts traps light energy and uses it to combine carbon dioxide and water to form glucose (food) and oxygen. The overall equation is: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ (in the presence of sunlight and chlorophyll).

Explanation

Green plants are autotrophs, meaning they make their own food. The process is called photosynthesis, where 'photo' means light and 'synthesis' means to make. It takes place in the green parts of the plant, mainly the leaves, inside cell organelles called chloroplasts. Chloroplasts contain the green pigment chlorophyll, which absorbs sunlight.

During photosynthesis, carbon dioxide from the air enters the leaf through tiny pores called stomata. Water and minerals absorbed by the roots are transported to the leaves through the xylem. Chlorophyll traps light energy and uses it to split water molecules into hydrogen and oxygen. The hydrogen combines with carbon dioxide to form glucose, which is the food. Oxygen is released as a by-product.

The glucose made is used by the plant for its growth and energy. Extra glucose is stored as starch in different parts such as leaves, stems, roots, fruits and seeds. The overall balanced chemical equation for photosynthesis is: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂. This process is the main source of food for all living organisms and also maintains the oxygen-carbon dioxide balance in the atmosphere.

Points to remember

  1. Photosynthesis: The process by which green plants prepare their own food using carbon dioxide, water and sunlight in the presence of chlorophyll.
  2. Site of photosynthesis: Chloroplasts in the leaf cells; chlorophyll is the green pigment that absorbs light energy.
  3. Raw materials: Carbon dioxide (from air through stomata), water (from soil through roots), and sunlight.
  4. Products: Glucose (C₆H₁₂O₆) as food and oxygen (O₂) as a by-product.
  5. Overall equation: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ (in the presence of sunlight and chlorophyll).

Exam tip

Write the balanced chemical equation of photosynthesis with conditions (sunlight and chlorophyll) and draw a labelled diagram of a leaf showing stomata and chloroplast if asked for 3 or 5 marks.

Questions students also ask

What are the raw materials required for photosynthesis?
The raw materials are carbon dioxide, water and sunlight. Carbon dioxide enters the leaf through stomata, water is absorbed by roots and transported through the xylem, and sunlight is absorbed by chlorophyll present in chloroplasts.
Why is photosynthesis important for life on Earth?
Photosynthesis is important because it produces food (glucose) for plants and indirectly for all other organisms. It also releases oxygen into the atmosphere, which is essential for respiration of most living beings, and removes carbon dioxide.
What is the role of stomata in photosynthesis?
Stomata are tiny pores on the surface of leaves. They allow the exchange of gases: carbon dioxide enters the leaf and oxygen (produced during photosynthesis) leaves the leaf. They also help in transpiration.

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