Photosynthesis

Introduction

Photosynthesis is the process by which green plants and some organisms convert sunlight, carbon dioxide, and water into glucose and release oxygen.
It is the primary source of energy in the food chain and critical for oxygen balance on Earth.
In Bihar, agriculture-based livelihoods depend heavily on photosynthesis-driven crop productivity.

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Photosynthesis: Basic Definition

• Occurs in green leaves containing chlorophyll
• Converts light energy → chemical energy
• Takes place in chloroplasts of plant cells
• Equation:
  6CO₂ + 6H₂O + Sunlight → C₆H₁₂O₆ + 6O₂
  (Carbon dioxide + Water + Sunlight → Glucose + Oxygen)

📝 PYQ (BPSC): What is the end product of photosynthesis? → Glucose
📝 Expected MCQ: Which pigment is essential for photosynthesis? → Chlorophyll

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Raw Materials Required

• Carbon dioxide → from atmosphere (via stomata)
• Water → absorbed by roots from soil
• Sunlight → provides energy
• Chlorophyll → traps solar energy

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Key Steps of Photosynthesis

1. Light Reaction

• Occurs in grana (thylakoid membrane)
• Uses sunlight to:
  • Split water → Hydrogen + Oxygen (photolysis)
  • Generate ATP and NADPH (energy molecules)

2. Dark Reaction / Calvin Cycle

• Occurs in stroma of chloroplast
• Uses ATP & NADPH to convert CO₂ → Glucose
• Does not require light directly

📝 Expected MCQ: Where does photolysis of water occur? → Grana
📝 Expected MCQ: Which cycle fixes carbon in dark reaction? → Calvin cycle

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Importance of Photosynthesis

• Produces oxygen → essential for respiration
• Stores solar energy in plants as glucose
• Base of food chain
• Maintains CO₂-O₂ balance in atmosphere
• Boosts crop yield, critical for Bihar’s economy

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Factors Affecting Photosynthesis

• Light Intensity: More light → higher rate
• CO₂ concentration: More CO₂ → faster rate
• Temperature: Optimum range 25–35°C
• Water availability: Needed for photolysis
• Chlorophyll level: More pigment → more synthesis

📝 Expected MCQ: Which factor does not affect photosynthesis? → Sound

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Bihar-Specific Relevance

• Photosynthesis affects crop productivity in rice, wheat, maize
• Use of shaded vs open-field crops impacts yield
• Bihar agricultural universities research on CO₂ responsiveness in crops
• Nitrogen deficiency in soil reduces chlorophyll → photosynthesis drops
• MNREGA & Agriculture schemes encourage plantation to boost O₂

📝 Expected MCQ: In Bihar, photosynthesis in crops is reduced due to...? → Nitrogen deficiency

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Related Concepts

• Stomata → Pores in leaves for gas exchange
• Chloroplast → Organelle where photosynthesis occurs
• Photolysis → Splitting of water using light
• ATP (Adenosine Triphosphate) → Energy currency of cell
• C₃ and C₄ Plants:
  • C₃: Wheat, Rice
  • C₄: Maize, Sugarcane (more efficient in high sunlight)

📝 Expected MCQ: Site of photosynthesis in plant cell? → Chloroplast

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PYQs + Expected MCQs

📝 PYQ (BPSC): What is the main product of photosynthesis? → Glucose
📝 PYQ: Which gas is released during photosynthesis? → Oxygen
📝 Expected MCQ: Name the organelle responsible for photosynthesis → Chloroplast
📝 Expected MCQ: Which element is essential for chlorophyll? → Magnesium

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Quick Revision Points

• Photosynthesis → CO₂ + H₂O → Glucose + O₂
• Occurs in chloroplast using chlorophyll
• Light Reaction → ATP, NADPH, O₂
• Dark Reaction → Glucose via Calvin Cycle
• Affected by: Light, CO₂, Water, Chlorophyll
• Bihar crops: Rice, Wheat → rely on efficient photosynthesis
• Stomata → Gas exchange pores on leaves

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Sources Used

• NCERT Class 10 Science – Life Processes
• Lucent GK – Biology Section
• Drishti Quick Book – Science
• EduTeria & Ghatna Chakra PYQs – BPSC, CDPO
• Bihar Agriculture Department – Crop Productivity Reports
• ICAR & Dr. Rajendra Prasad Agricultural University (Bihar) Research Papers