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What are the steps included in photosynthesis? |
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Answer» Very nice answer Photosynthesis comprises two phases.Light-dependent reaction (or) Light reaction: Photosynthesis begins with the light reaction which is carried out only during the day in the presence of sunlight. In plants, the light-dependent reaction takes place in the thylakoid membranes of chloroplasts. The Grana, membrane-bound sacs like structures present inside the thylakoids functions by gathering light and is called as photosystems. These photosystems have large complexes of pigment and proteins molecules present within the plant cells which plays the primary role during the process of light reactions. There are two types of photosystems: photosystem I and photosystem II.Under the light-dependent reactions, the light energy is converted to ATP and NADPH which are used in the second phase of photosynthesis. During the light reactions, ATP and NADPH are generated by two electron transport chains, water is used and oxygen is produced.The chemical equation in the light reaction can be reduced to:\t2H2O + 2NADP+ + 3ADP + 3Pi → O2 + 2NADPH + 3ATP\tLight-independent reaction (or) Dark reaction.Dark reaction is also called carbon-fixing reaction. It is a light-independent process in which sugar molecules are formed from the water and carbon dioxide molecules. The dark reaction occurs in the stroma of the chloroplast where they utilize the NADPH and ATP products of the light reaction. Plants capture the carbon dioxide from the atmosphere through stomata and proceed to the Calvin cycle. In the Calvin cycle, the ATP and NADPH formed during light reaction drive the reaction and convert 6 molecules of carbon dioxide into one sugar molecule or glucose.The chemical equation for the dark reaction can be reduced to:\t3CO2 + 6 NADPH + 5H2O + 9ATP → G3P + 2H+ + 6 NADP+ + 9 ADP + 8 Pi\t 4 steps... absorption of light energy by chlorophyll, conversion of light energy into chemical energy, splitting of water molecules into hydrogen and oxygen, reduction of carbon dioxide to carbohydrates... |
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