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| Points to Remember |
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 Equation of photosynthesis |
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Rate of photosynthesis is high in red and blue light. |
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Chlorophyll pigments - chl.a - porphyrin head with CH3 group and phytol chain. Chl.b - porphyrin head with CHO group and phytol chain. |
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| Accessory pigment - which pass electrons to primary pigments. |
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Photon - unit of light energy. |
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Light reaction (grana) Trapping of solar energy by chlorophyll and its storage as ATP and NADPH. |
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Photophoshorylation - Synthesis of ATP from ADP and Pi in light. |
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Photolysis of water: Splitting of water into 2H + 2e- and ½ O2 in the presence of sunlight. |
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Cyclic photophosphorylation - electron emitted by PS-I comes back to it after passing through ETC. |
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Non - cyclic photophosphorylation - electrons released by PS-II (P680) do not come back to it but accepted by PS-I (P700) after passing through ETC. ATP, NADPH and O2 are produced. |
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Dark reaction - Conversion of CO2 into carbohydrates using NADPH and ATP |
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| Steps |
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| - Carboxylation |
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| - Glycolytic reversal |
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| - Regeneration of RUBP |
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Photorespiration |
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| Light dependent up take of O2 by cells and release of CO2 without producing ATP and NADPH. |
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| During high conc. of O2 and high temperature. |
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| RUBISCO act as RUBP oxygenase. RUBP splits into PGA and phosphoglycolate. |
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Drawbacks: 50% of CO2 fixed is lost. |
| - ATP and NADH not produced |
| - Undoes the work of photosynthesis |
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C4 pathway (Sorghum, Sugarcane, Maize) |
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| C4 cycle |
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| Concentration of CO2 increases in bundle sheath cells. Rubisco acts as carboxylase enzyme. Calvin cycle starts and glucose is synthesised. |
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Advantage of C4 pathway |
| - Photorespiration does not occur |
| - Glucose is synthesized even when concentration of CO2 is low. |
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Molecules of ATP used during |
| - C3 pathway - 18 ATP for synthesis of one molecule of glucose |
| - C4 pathway - 30 ATP |
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Autotropic and heterotropic nutrition |
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Heterotropic nutrition consists of parasitic, symbiotic, saprophytic nutrition. |
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Insectivorous plants are autotrophs but depend on insects for animal nitrogen. |
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