🌱 Photosynthesis – Class 11 Notes for NEET & CBSE Students

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Introduction
Photosynthesis is one of the most important life processes on Earth. It is the process by which green plants, algae, and some bacteria use sunlight to prepare their own food. For students preparing for CBSE Class 11 or NEET 2025, photosynthesis is a high-weightage topic that requires clear understanding. In this blog, we will simplify the concept with definitions, diagrams, and important points.


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📌 What is Photosynthesis?

Photosynthesis is the process by which green plants convert carbon dioxide and water into glucose and oxygen in the presence of sunlight and chlorophyll.

Equation of Photosynthesis:

6CO_2 + 12H_2O \xrightarrow[\text{Chlorophyll}]{\text{Light}} C_6H_{12}O_6 + 6O_2 + 6H_2O

👉 This equation shows how plants make food (glucose) and release oxygen, which is essential for all living organisms.


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📌 Where Does Photosynthesis Take Place?

Site: Photosynthesis occurs in chloroplasts.

Pigments Involved: Chlorophyll a, Chlorophyll b, carotenoids, and xanthophylls.

Main Pigment: Chlorophyll a (essential for light absorption).



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📌 Stages of Photosynthesis

1. Light Reaction (Photochemical phase):

Takes place in the thylakoid membrane of chloroplast.

Involves light absorption, splitting of water (photolysis), release of oxygen, and formation of ATP and NADPH.



2. Dark Reaction (Biosynthetic phase/Calvin Cycle):

Takes place in the stroma of chloroplast.

Involves fixation of carbon dioxide into glucose.

Uses ATP and NADPH from light reaction.





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📌 Factors Affecting Photosynthesis

Light Intensity – More light = higher rate of photosynthesis (up to a limit).

Carbon Dioxide Concentration – More CO₂ increases photosynthesis up to saturation point.

Temperature – Photosynthesis is enzyme-dependent; optimum temperature is required.

Water Availability – Water stress reduces photosynthesis.



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📌 Importance of Photosynthesis

✅ Provides food (glucose) for plants and indirectly for all animals.
✅ Produces oxygen for respiration.
✅ Maintains balance of CO₂ and O₂ in the atmosphere.
✅ Forms the basis of life on Earth.


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📌 NEET/CBSE Exam Tip

Chlorophyll a is the main pigment in photosynthesis.

Light reaction occurs in grana, dark reaction in stroma.

Calvin cycle was discovered by Melvin Calvin.



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📌 Conclusion

Photosynthesis is not just a biological process; it is the reason life exists on Earth. For NEET and CBSE Class 11, mastering the concepts, equations, and factors of photosynthesis is very important. Keep revising with diagrams and previous year questions.

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