🌿 Photosynthesis in Higher Plants – NEET Summary & Practice

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🌞 Introduction

Photosynthesis is the biochemical process by which green plants convert solar energy into chemical energy. Understanding this chapter is crucial for NEET 2025, as it involves key concepts like light reactions, C3 and C4 cycles, and photorespiration.


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🌱 Key Concepts at a Glance

📌 1. Photosynthesis Equation

6CO₂ + 6H₂O + sunlight → C₆H₁₂O₆ + 6O₂

📌 2. Site of Photosynthesis

Occurs in chloroplasts

Thylakoids: Light reactions

Stroma: Dark reactions


📌 3. Pigments

Chlorophyll a (main pigment)

Accessory pigments: chlorophyll b, carotenoids, xanthophylls



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⚡ Light Reaction (Photochemical Phase)

Occurs in thylakoid membranes

Involves photolysis of water, ATP synthesis, and NADPH formation

Includes Photosystem I (PSI) and Photosystem II (PSII)


Major steps:

Non-cyclic photophosphorylation – both PSI & PSII involved

Cyclic photophosphorylation – only PSI used; no O₂ or NADPH formed



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🧪 Dark Reaction (Biosynthetic Phase)

Calvin Cycle (C₃ pathway)

First stable product: 3-PGA

Enzyme: RuBisCO


C₄ Cycle

First stable product: Oxaloacetic acid (OAA)

More efficient in high temperature




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🌬️ Photorespiration

Wasteful pathway

Involves oxygenation of RuBP

Occurs in C₃ plants

Not seen in C₄ plants due to spatial separation of Calvin cycle and initial CO₂ fixation



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📝 NEET Practice Questions

1. Which pigment is directly involved in light reactions?
A. Chlorophyll b
B. Carotene
C. Chlorophyll a
D. Xanthophyll
✅ Answer: C. Chlorophyll a

2. The first stable product of C4 cycle is:
A. PGA
B. Pyruvate
C. OAA
D. Malate
✅ Answer: C. OAA

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