Question

During light reaction in photosynthesis the following are formed.

• A. $ATP$ and sugar
• B. hydrogen, $O_{2}$ and sugar
• C. $ATP$, hydrogen donor and $O_{2}$
• D. $ATP$, hydrogen and $O_{2}$ donor

Answer 1

Answer: (C)

$ATP$, hydrogen donor and $O_{2}$

Answer 2

Light reactions occur inside thylakoids. It is dependent upon light. It involves photolysis of water (breaking of water into $H_{2}$ and $O_{2}$) and production of assimilatory power ($NADPH$ and $ATP$). Electron released during photolysis of water are picked up by Peso photocentre of photosystem $II$. From here electrons passes over series of carrier which include $PQ$, cytochrome $b-f$ complex and $PC$. While passing over cytochrome complex, the electron losses sufficient energy for creation of proton gradient and $ATP$ from $ADP$ and inorganic phosphate. From $PC$ electron is picked by the trap centre $P_{700}$ of photosystem $I$, which pushes out electron after absorbing light energy. Electron passes over carriers $FeS$, ferredoxin and $NADP$-reductase which gives electron to $NADP^{+}$ for combining with $H^{+}$ to produce $NADPH$. $NADP^{+} + 2e^{-} + H^{+} {->[][NADP{\text{reductase}}]}NADPH$