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Life Processes — Science STD 10 — Question

CBSE BoardEnglish MediumSTD 10ScienceLife Processes5 Marks
Question
Mention the major events during photosynthesis.
✓

Answer

1. Photolysis: With the help of light energy, oxygen evolving Z-complex splits up water into its components- protons ( $H ^{+}$), electrons ( $e ^{-}$) and oxygen.
$2 H_2 O \xrightarrow[Mn, Ca, Cl]{OEC} O_2+4 H^{+}+4 e^{-}$
2. Absorption of Light Energy: Chlorophyll absorbs light energy.
3. Primary Reaction: Chlorophyll converts the absorbed light energy into chemical energy. It is called primary reaction of photosynthesis. It builds up ATP with the help of excited electrons.
4. Formation of Reducing Power: Coenzyme NADP ${ }^{+}$is changed to reduced form of NADPH.
$NADP^{+}+H^{+}+2 e^{-} \rightarrow NADPH$
5. Reduction of $CO _2$ : Carbon dioxide is reduced enzymatically with the help of NADPH and ATP to form carbohydrates.
$6 CO_2+12 NADPH+18 ATP \rightarrow C_6 H_{12} O_6+12 NADP^{+}+18 ADP+18 Pi$

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