Photosynthesis in Higher Plants for NEET UG
Photosynthesis turns light energy into the chemical energy in sugar, and it feeds almost every food chain on Earth. Follow the light reactions, then the Calvin cycle, then the C₄ shortcut.
BiologyClass 1178 MCQs2 lessons13 flashcards3 memory tricks
Practise Photosynthesis in Higher Plants free
What you'll learn
- Light reactions
Describe where the light reactions happen and what they produce. - The Calvin cycle and the C₄ pathway
Explain carbon fixation in C₃ and C₄ plants, and why photorespiration matters.
Key formulas
| Overall equation | 6CO₂ + 12H₂O → C₆H₁₂O₆ + 6O₂ + 6H₂O (with light and chlorophyll) |
|---|---|
| To make one glucose | 6 turns of the cycle, 18 ATP, 12 NADPH |
Memory tricks
Light reactions in the thylakoids (grana) make ATP, NADPH and O₂. The Calvin cycle in the stroma uses them to fix CO₂.
In the Z-scheme, electrons go from water to PS II (P680) and then to PS I (P700) before reaching NADP⁺.
C₄ plants have Kranz anatomy and concentrate CO₂ round RuBisCO, so there is almost no photorespiration. C₃ plants lose carbon to photorespiration at high temperature.
Try 3 NEET-style questions
Q1. Cyclic photophosphorylation involves
- both photosystems and produces NADPH
- only PS II and releases O₂
- only PS I and makes ATP but not NADPH
- the Calvin cycle in the stroma
Show answer
Answer: (3) only PS I and makes ATP but not NADPH
In cyclic photophosphorylation only PS I works; the excited electron cycles back, so ATP is made but NADPH is not. It occurs in the stroma lamellae.
Q2. The oxygen released in photosynthesis comes from
- carbon dioxide
- glucose
- water
- chlorophyll
Show answer
Answer: (3) water
Photolysis of water releases O₂ (shown by isotope studies and Van Niel's work).
Q3. In the non-cyclic flow of electrons, the final acceptor of electrons is
- O₂
- water
- NADP⁺
- CO₂
Show answer
Answer: (3) NADP⁺
Electrons from PS I are passed to NADP⁺, which is reduced to NADPH + H⁺.
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