Introduction

Photosynthesis is the process by which green plants convert light energy into chemical energy, producing glucose and oxygen from carbon dioxide and water. This process is crucial for life on Earth, as it provides food and oxygen.

In NEET, questions often cover light and dark reactions, Calvin cycle, C3 and C4 pathways, photosynthetic pigments, and stoichiometric formulas.

Direct Links to Download 2025-26 Formula Biology (PDF)

► Click “Download Now” next to your subject to access the free PDF.

♦ The Living World ⇒ Download Now

♦ Biological Classification ⇒ Download Now

♦ Plant Kingdom ⇒ Download Now

♦ Animal kingdom ⇒ Download Now

♦ Morphology of Flowering Plants ⇒ Download Now

♦ Anatomy of Flowerng Plants ⇒ Download Now

♦ Structural Organisation in Animals ⇒ Download Now

♦ Cell-The Unit of Life ⇒ Download Now

♦ Cell Cycle and Cell Division ⇒ Download Now

♦ Photosynthesis in Higher Plants ⇒ Download Now

♦ Respiration in Plants ⇒ Download Now

♦ Plant, Growth and Development ⇒ Download Now

♦ Sexual Reproduction in Flowering Plants ⇒ Download Now

♦ Human Reproduction ⇒ Download Now

♦ Reproductive Health ⇒ Download Now

♦ Principles of Inheritance and Variation ⇒ Download Now

♦ Molecular Basis of Inheritance ⇒ Download Now

♦ Human Health and Diseases ⇒ Download Now

♦ Strategies for Enhancement in Food Production ⇒ Download Now

♦ Microbes in Human Welfare ⇒ Download Now

♦ Biotechnology - Principles and Processes ⇒ Download Now

♦ Biotechnology and its Application⇒ Download Now

♦ Organisms and Populations ⇒ Download Now

♦ Ecosystem ⇒ Download Now

♦ Biodiversity and its Conservation ⇒ Download Now

♦ Environmental Issues ⇒ Download Now

♦ Body Fluid and Circulation ⇒ Download Now

♦ Excretory Products and Their Elimination ⇒ Download Now

♦ Locomotion and Movement ⇒ Download Now

♦ Neural Control and Coordination ⇒ Download Now

♦ Chemical Coordination and Intergration ⇒ Download Now

♦ Breathing and Exchange of Gases ⇒ Download Now

1. Site of Photosynthesis

• Chloroplasts are the primary site in higher plants.

• Key structures: Thylakoids (grana) – light reaction, stroma – dark reaction (Calvin cycle).

• Pigments involved:

  • Chlorophyll a (main pigment)

  • Chlorophyll b (accessory)

  • Carotenoids (accessory, photoprotection)

NEET Tip:

• Thylakoid membranes → Light reaction → ATP, NADPH

• Stroma → Dark reaction → Glucose

2. General Photosynthesis Equation

6CO2+12H2O+Light⟶C6H12O6+6O2+6H2O6CO_2 + 12H_2O + Light \longrightarrow C_6H_{12}O_6 + 6O_2 + 6H_2O6CO2​+12H2​O+Light⟶C6​H12​O6​+6O2​+6H2​O

Simplified Formula for NEET:

• Carbon fixation: 6 CO₂ → 1 glucose (C₆H₁₂O₆)

• Oxygen evolution: From water splitting

3. Light Reaction (Photochemical Phase)

• Occurs in thylakoid membranes

• Requires light, water, ADP, NADP⁺

• Main events:

  • Photolysis of water: H₂O → 2H⁺ + ½O₂ + 2e⁻

  • ATP synthesis: Via photophosphorylation

  • NADPH formation: Light energy reduces NADP⁺

NEET Formula Shortcut:

• Light + H₂O + ADP + NADP⁺ → ATP + NADPH + O₂

Key Points for NEET:

• Oxygen released → Splitting of water (photolysis)

• Light is absorbed by chlorophyll a

4. Dark Reaction (Calvin Cycle / Carbon Fixation)

• Occurs in stroma of chloroplasts

• Does not require light directly

• Uses ATP and NADPH from light reaction

• Main stages:

  1. Carbon fixation: CO₂ + Ribulose-1,5-bisphosphate (RuBP) → 3-phosphoglycerate (3-PGA)

  2. Reduction: 3-PGA → G3P using ATP and NADPH

  3. Regeneration of RuBP: G3P used to regenerate RuBP for cycle continuation

NEET Shortcut Formula:

• 3 CO₂ + 9 ATP + 6 NADPH → 1 G3P (triose phosphate)

Glucose Formation:

• 2 G3P → 1 Glucose (C₆H₁₂O₆)

5. C3, C4, and CAM Pathways

C3 Plants:

• Fix CO₂ directly via Calvin cycle → 3-PGA

• Examples: Rice, Wheat, Soybean

• NEET Tip: Most common photosynthetic pathway

C4 Plants:

• Initial CO₂ fixation → Oxaloacetate (4C compound)

• Occurs in mesophyll cells → bundle sheath cells

• Examples: Maize, Sugarcane, Sorghum

• Advantage: Efficient in hot, dry conditions (reduces photorespiration)

CAM Plants:

• CO₂ fixed at night, used in Calvin cycle during the day

• Example: Cactus, Pineapple

• Adaptation to arid conditions

6. Factors Affecting Photosynthesis

1. Light: Intensity and wavelength (red and blue most effective)
2. CO₂ Concentration: Rate increases with CO₂ up to saturation
3. Temperature: Optimal 25–35°C for most plants
4. Water Availability: Water stress reduces photolysis
5. Chlorophyll Content: Less chlorophyll → slower photosynthesis

NEET Tip:

• Questions often ask about limiting factors and adaptations

7. NEET Important Formulas / Stoichiometry

1. Light reaction: H₂O + Light → O₂ + ATP + NADPH

2. Calvin cycle: 3 CO₂ + 9 ATP + 6 NADPH → G3P → ½ Glucose

3. Overall photosynthesis: 6 CO₂ + 12 H₂O → C₆H₁₂O₆ + 6 O₂ + 6 H₂O

4. C3 pathway → 3-PGA, C4 pathway → Oxaloacetate, CAM → Night CO₂ fixation

Mnemonic for Photosynthetic Pigments:
“Chl a is Active, Chl b is Backup, Carotenoids Protect”

8. Special NEET Points

• Photophosphorylation types:

  • Cyclic → Only ATP

  • Non-cyclic → ATP + NADPH + O₂

• Limiting factor → The factor at which photosynthesis is blocked first

• Photorespiration → Loss of fixed CO₂ in C3 plants

9. NEET Exam Tips

• Draw chloroplast with grana and stroma, label light and dark reactions

• Memorize light → ATP/NADPH/O₂, dark → glucose via Calvin cycle

• Focus on C3, C4, and CAM plants differences

• Use formulas for quick numerical MCQs

Conclusion

Photosynthesis in higher plants is a high-yield topic in NEET Biology. Mastery of light and dark reactions, Calvin cycle, and C3/C4 pathways is essential for scoring in MCQs and diagram-based questions.

With this StudentBro.in guide, students can efficiently revise photosynthesis formulas, stages, and adaptations, enhancing speed and accuracy during NEET exams.

Remember: Linking site → pigment → reaction → product is the key to mastering Photosynthesis in Higher Plants.