🌈 4 Pigments in Photosynthesis

Leaf colors come from four pigments working together:

  • ✨ Chlorophyll a: Bright blue-green (main pigment)
  • ✨ Chlorophyll b: Yellow-green
  • ✨ Xanthophylls: Yellow
  • ✨ Carotenoids: Yellow to yellow-orange

We find these using paper chromatography! 🧪

🔬 How Pigments Work

Chlorophyll a is the superstar 🌟:

  • Absorbs light best in blue and red regions (see graph 11.3a)
  • Photosynthesis peaks where chlorophyll a absorbs most light (graph 11.3b)

But the other pigments (accessory pigments) help too!

  • They capture light chlorophyll a misses 🌈
  • Pass energy to chlorophyll a → teamwork!
  • Protect chlorophyll a from damage 🛡️

Fun fact: More pigments = more shades of green in leaves! 🍃

⚡ Light Reaction (Photochemical Phase)

When light hits leaves, here’s what happens:

  1. Light absorption 🌞
  2. Water splitting 💧 → oxygen release 💨
  3. Creation of energy carriers: ATP and NADPH 🔋

🧩 Photosystems: Nature’s Light Factories

Pigments are organized into two teams:

  • Photosystem I (PS I) and Photosystem II (PS II)
  • Each has a Light Harvesting Complex (LHC) with hundreds of pigment molecules 🧪
  • LHC acts like an “antenna” catching light waves 📡

Every photosystem has:

  • Many pigments (chlorophyll b, xanthophylls, carotenoids) gathering light
  • ONE special chlorophyll a molecule as the reaction centre 🎯

🔋 Reaction Centres: The Energy Converters

  • In PS I: Chlorophyll a absorbs 700 nm light → called P700
  • In PS II: Chlorophyll a absorbs 680 nm light → called P680

These reaction centres turn light into chemical energy! ⚡

🔁 Electron Transport

Here’s the energy shuffle in PS II:

  1. Light hits P680 → electrons get excited and jump! 💥
  2. Electrons grabbed by electron acceptor
  3. Sent down an electron transport chain (like a slide!) 🎢
  4. This chain helps make ATP (energy currency)

💡 NEET Must-Knows

  1. 4 pigments: Chlorophyll a, b + xanthophylls + carotenoids
  2. Chlorophyll a is the primary pigment (absorbs blue/red light best)
  3. Accessory pigments extend light absorption + protect chlorophyll a
  4. Photosystems: PS I (P700) and PS II (P680) with antenna pigments + reaction centres
  5. Light reaction outputs: ATP, NADPH, and O2 from water splitting