Edexcel iGCSE Biology-2.18 Process of Photosynthesis- Study Notes- New Syllabus

Photosynthesis – Conversion of Light Energy to Chemical Energy

📝 Introduction

Plants, algae, and some bacteria can make their own food → autotrophs.
They do this by photosynthesis: a process where light energy is converted into chemical energy (glucose).
This chemical energy can later be stored or used in respiration.

🔑 Definition of Photosynthesis

👉 Photosynthesis is the process by which green plants use chlorophyll to absorb light energy and convert carbon dioxide + water into glucose, releasing oxygen as a by-product.

Equation (word):
Carbon dioxide + Water → Glucose + Oxygen
(light energy + chlorophyll)

Equation (symbols):
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

☀️ Role of Light Energy

• Chlorophyll (in chloroplasts) absorbs sunlight.
• Light energy is transformed into chemical bonds in glucose molecules.
• This energy is now in a form that both plants and animals can use.

🎯 Importance of Photosynthesis

• Source of Food
  Produces glucose → used in respiration, stored as starch, or converted into cellulose, proteins, fats.
• Source of Energy for Life
  Chemical energy in glucose passes through food chains (plants → herbivores → carnivores).
• Produces Oxygen
  Essential for aerobic respiration in most living organisms.
• Removes Carbon Dioxide
  Helps regulate atmospheric CO₂ and reduce greenhouse gases.

👉 Without photosynthesis → no food, no oxygen, no life.

📊 Summary Table

⚡ Quick Recap 
Definition: Light energy → chemical energy (glucose) using chlorophyll.
Equation: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂.
Importance: Produces food, energy, oxygen, reduces CO₂.
Chlorophyll = key for capturing sunlight.
👉 Mnemonic: “Photosynthesis = Light → Life” 🌍