Photosystems & Light-Harvesting Complexes — NEET Biology
✅ Asked in NEET 2026Light reactions or the 'Photochemical' phase include light absorption, water splitting, oxygen release, and the formation of high-energy chemical intermediates, ATP and NADPH. Several protein complexes are involved in the process. The pigments are organised into two discrete photochemical light harvesting complexes (LHC) within the Photosystem I (PS I) and Photosystem II (PS II). These are named in the sequence of their discovery, and not in the sequence in which they function during the light reaction. The LHC are made up of hundreds of pigment molecules bound to proteins. Each photosystem has all the pigments (except one molecule of chlorophyll a) forming a light harvesting system also called antennae. These pigments help to make photosynthesis more efficient by absorbing different wavelengths of light. The single chlorophyll a molecule forms the reaction centre. The reaction centre is different in both the photosystems. In PS I the reaction centre chlorophyll a has an absorption peak at 700 nm, hence is called P700, while in PS II it has absorption maxima at 680 nm, and is called P680.
NTA tests your understanding of how PS I and PS II work, particularly the distinction between light-harvesting antennae (hundreds of pigments) and the reaction centre (single P680 or P700 chlorophyll a). Students often confuse the naming: PS II is named second but functions first during light reactions—this reversal trips many up. The key trap is mixing up P680 (PS II, 680 nm) with P700 (PS I, 700 nm). Remember: antennae absorb various wavelengths to maximize efficiency, but only the reaction centre chlorophyll a actually initiates charge separation. This concept appears because it connects structure to function in photosynthesis.
This paragraph was tested 3 times in NEET.
Find the incorrect statements about photosynthesis: A. Water splitting complex is associated with PS I. B. C4 plants use C3 pathway as main biosynthetic pathway. C. In C4 plants, photorespiration does not occur. D. C3 plants exhibit Kranz anatomy. E. ATP synthesis in chloroplast occurs through chemiosmosis.
Which of the following are required for the light reaction of photosynthesis? (NEET 2024) A. CO₂ B. O₂ C. H₂O D. Chlorophyll E. Light
(NEET 2024) The photochemical phase of photosynthesis includes: A. Oxygen release B. Formation of NADPH C. Use of ATP D. Water splitting E. Carboxylation
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