Photosynthesis — Grade 11 Explained

🔍 What is Photosynthesis?

Photosynthesis is the process by which green plants, algae, and some bacteria use sunlight to make their own food (glucose) from carbon dioxide and water.

👉 It happens mainly in the chloroplasts of plant cells.

🧪 The Photosynthesis Equation

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Meaning:

Carbon dioxide + water + light energy → glucose + oxygen

🌞 Two Main Stages of Photosynthesis

1. Light-Dependent Reactions (Light Stage)

📍 Happens in the thylakoids (inside chloroplasts)

What happens:

Sunlight is absorbed by chlorophyll

Water (H₂O) is split → releases oxygen (O₂)

Energy is stored as ATP and NADPH

👉 Oxygen you breathe comes from this stage!

2. Light-Independent Reactions (Calvin Cycle)

📍 Happens in the stroma (fluid inside chloroplast)

What happens:

Uses CO₂ from the air

Uses ATP & NADPH from the light stage

Produces glucose (C₆H₁₂O₆)

👉 This is where food (sugar) is actually made.

🍃 Structure of a Leaf (Important for Photosynthesis)

Chloroplasts → contain chlorophyll (green pigment)

Stomata → tiny pores for gas exchange (CO₂ in, O₂ out)

Xylem → transports water

Phloem → transports glucose

⚙️ Factors Affecting Photosynthesis

Light intensity ☀️

Carbon dioxide concentration 🌬️

Temperature 🌡️

Water availability 💧

👉 If one factor is low, photosynthesis slows down (limiting factor concept).

💡 Why Photosynthesis is Important

Produces oxygen for breathing

Provides food (glucose) for plants (and indirectly for animals)

Forms the base of food chains

Helps reduce carbon dioxide in the atmosphere

📌 Quick Summary

Occurs in chloroplasts

Has 2 stages: Light stage + Calvin cycle

Uses CO₂ + H₂O + light

Produces glucose + O₂