Class 11 NEET Biology Photosynthesis in Higher Plants

(c) : Photosynthesis is actually oxidation reduction process in which water is oxidised and CO2 is reduced to carbohydrates. The reduction of CO2 to carbohydrates needs assimilatory powers, i.e., ATP and NADPH ‌2. The process of photosynthesis involves two steps-
(i) Light dependent phase or photochemical reaction.
(ii) Light independent phase or dark reaction.
In Calvin cycle, CO2 acceptor molecule is RuBP or RuBP. The enzyme catalyzing this reaction is RuBPcarboxylase\/oxygenase (RuBisCO). As Calvin cycle takes in only one carbon (as CO2 ) at a time, so it takes six turns of the cycle to produce a net gain of six carbons ( i.e., hexose or glucose). In this cycle, for formation of one mole of hexose sugar (Glucose), 18 ATP and 12 NADPH ‌2 are used. For 6 molecules of CO2 it needs 18 ATP and 12 NADPH molecules so for assimilation of one molecule of CO2 it needs 3 ATP and 2 NADPH ‌2 molecules.