Photosynthesis is the process by which green plants prepare their own food using sunlight. Plants that make their own food are called autotrophs, and this is a key exam topic.
The Process
Plants use carbon dioxide, water and sunlight to produce glucose and release oxygen. The green pigment chlorophyll traps sunlight. The reaction takes place in the chloroplast.
Word Equation
Carbon dioxide + Water → (in sunlight and chlorophyll) → Glucose + Oxygen.
Requirements
- Sunlight: source of energy.
- Chlorophyll: traps light.
- Carbon dioxide: taken in through stomata.
- Water: absorbed by the roots.
Stomata
Stomata are tiny pores on the surface of leaves. They allow exchange of gases and release water vapour during transpiration. Each stoma is guarded by two guard cells.
Plant Nutrition
Plants need nutrients like nitrogen, phosphorus and potassium from the soil. Insectivorous plants like the pitcher plant trap insects to get nitrogen. The food made in photosynthesis is stored as starch.
Quick Revision Points
- Photosynthesis takes place in the chloroplast.
- Chlorophyll traps sunlight.
- Products are glucose and oxygen.
- Stomata allow gas exchange in leaves.
- Plants are called autotrophs.
- Food is stored as starch.
- Raw materials are CO2 and water.