🌿 Plastic Metabolism: Photosynthesis
How living organisms build complex molecules using light energy
Grade 9 Biology — Cell Biology🔬 Section 1: What Is Metabolism?
Metabolism encompasses all chemical reactions occurring inside a living cell. It is divided into two complementary branches:
⬆️ Anabolism (Plastic / Constructive Metabolism)
- Builds small molecules into larger, more complex organic molecules
- Requires energy input (usually ATP)
- Examples: photosynthesis, protein synthesis, DNA replication
Think: "building up" 🏗️
⬇️ Catabolism (Destructive Metabolism)
- Breaks larger molecules into smaller ones
- Releases energy (stored as ATP)
- Examples: cellular respiration, digestion of food
Think: "breaking down" 💥
Key Insight: Photosynthesis is the premier example of plastic (anabolic) metabolism — it forms substances like glucose from simple inorganic molecules (CO₂ and H₂O) using sunlight energy.
📊 Anabolism vs. Catabolism — Energy Comparison
Interactive visualization — available in the full lesson