Key Points — Core Concepts — Summary

Overall equation: $6CO_{2}$ + 12 $H_{2}O$ → $C_{6}H_{12}O_{6}$ + 6 $H_{2}O$ + $6O_{2}$ (12 $H_{2}O$ confirmed by Van Niel; $O_{2}$ from water)
Location: Light reactions = thylakoid membranes (grana); Calvin cycle = stroma; Cyclic photophosphorylation = stroma lamellae
Primary pigment: Chlorophyll a (P680 in PS II, P700 in PS I); all others are accessory pigments
PS I vs PS II: PS II acts FIRST (splits water, P680, 680 nm); PS I acts SECOND (makes NADPH, P700, 700 nm) — numbering reflects discovery order, not function
Hill reaction: Photolysis of water at PS II: 2 $H_{2}O$ → 4 $H^{+}$ + 4 $e^{-}$ + $O_{2}$
Z-scheme order: PS II → PQ → Cyt b6f → PC → PS I → Fd → NA $DP^{+}$ reductase → NADPH
Non-cyclic photophosphorylation: Both PS I + PS II → ATP + NADPH + $O_{2}$ (grana)
Cyclic photophosphorylation: PS I only → ATP only (stroma lamellae) — no NADPH, no $O_{2}$
Chemiosmosis: $H^{+}$ (from photolysis + PQ shuttle) accumulates in thylakoid lumen → $CF_{0}$ - $CF_{1}$ ATP synthase → ATP
Calvin cycle (CRR): Carboxylation (C $O_{2}$ + RuBP → 2×3-PGA, RuBisCO) → Reduction (3-PGA → G3P, ATP+NADPH) → Regeneration (G3P → RuBP, ATP)
Calvin cycle stoichiometry: 6 turns = 1 glucose = 18 ATP + 12 NADPH (18 not 12 ATP — NEET trap)
C4 plants: Kranz anatomy; PEP carboxylase (mesophyll) → OAA (4C, first product) → malate → bundle sheath → Calvin cycle (RuBisCO); no photorespiration; examples: maize, sugarcane, sorghum
CAM plants: Temporal separation; PEP carboxylase (night) → malic acid (stored in vacuole); Calvin cycle (day, stomata closed); examples: cacti, Bryophyllum, pineapple
Photorespiration: RuBisCO oxygenase activity → phosphoglycolate → C2 cycle → C $O_{2}$ released, no ATP; absent in C4/CAM
Blackman's law: Rate = limited by factor in minimum supply (light, C $O_{2}$ , temperature)