Photosynthesis – CHEMASH Biology
Photosynthesis is the process by which green plants prepare their own food using sunlight, carbon dioxide and water in the presence of chlorophyll. This chapter is extremely important for Class 9, Class 11, Boards & NEET 2026.
Related Topics: Cell Organelles | Biomolecules | Enzymes & Metabolism
Table of Contents
- Definition & Equation
- Site of Photosynthesis
- Light Reaction
- Dark Reaction (Calvin Cycle)
- Factors Affecting Photosynthesis
- Importance
- MCQs
- FAQs
Definition & Equation
Photosynthesis converts light energy into chemical energy stored in glucose.
Balanced Equation:
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ (in presence of sunlight & chlorophyll)
Site of Photosynthesis
Photosynthesis occurs in chloroplast of plant cells. Chloroplast contains:
- Grana (site of light reaction)
- Stroma (site of dark reaction)
- Chlorophyll pigment
Light Reaction (Photochemical Phase)
Occurs in the grana. It requires sunlight.
- Splitting of water (Photolysis)
- Release of Oxygen
- Formation of ATP & NADPH
Important for NEET: Photolysis occurs in thylakoid membrane.
Dark Reaction (Calvin Cycle)
Occurs in stroma. Does not require direct sunlight.
- Uses ATP & NADPH from light reaction
- Fixes carbon dioxide
- Produces glucose
Scientist: Melvin Calvin (Nobel Prize)
Factors Affecting
- Light intensity
- Carbon dioxide concentration
- Temperature
- Water availability
Importance
- Produces oxygen
- Primary source of food
- Maintains carbon cycle
- Supports all life on Earth
MCQs with Explanation (2026)
1. Site of light reaction?
Answer: Grana
Explanation: Occurs in thylakoid membranes.
2. Calvin cycle occurs in:
Answer: Stroma
Explanation: Dark reaction takes place in stroma.
3. Oxygen released comes from:
Answer: Water
Explanation: Due to photolysis of water.
4. Photosynthesis converts:
Answer: Light energy into chemical energy.
FAQs
Q1. Does dark reaction occur at night?
A: Not necessarily. It does not require light but usually occurs during day.
Q2. Who discovered Calvin Cycle?
A: Melvin Calvin.
Official reference: NCERT Biology Textbook
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