Photosynthesis
(Photo means light & synthesis means preparation food)
Photosynthesis is the process used by the plants to synthesis their own food with the help of carbon dioxide, water & chlorophyll in the presence of sunlight.
Site of Photosynthesis
Chloroplast:-
- All green parts of plant including green stems & unripened fruit have chloroplast . But the leaves are major site of photosynthesis in plant.
- Chloroplast are found in the cells of the mesophyll. ( Tissue in the interior of the leaf)
- Carbon Dioxide enter leaf & oxygen exits excrete through microscopic pore called stomata.
- Water absorbed by roots and delivered to leaves in veins (xylem).
- Sugar which synthesize in leaves also export to roots & other non photosynthetic parts of the plants through phloem.
Mechanism of Photosynthesis
Photosynthesis occurs in two phases :
1. Light Reaction
2. Dark Reaction
Light Reaction
Solar energy is trapped by chlorophyll and stored in the form of chemical energy (ATP) and as reducing power (NADPH).
This photochemical reaction is also known as Hill reaction in which water splits by the excited pigments in presence of sunlight resulting in release of oxygen, hydrogen & electron. These electrons carried by a number of electron carriers and ultimately accepted by NADP. Also accepting proton, NADP gets reduced to NADPH2 which is highly reducing substance that reduces carbon dioxide during dark reaction. During flow of electrons some amount of energy is released which couples ADP and inorganic phosphate into ATP by the process known as photophosphorylation.
Thylakoids perform the light reaction as they possess both pigments system and ATPase of light energy falls on pigment molecule , they become excited and exit light energy. All these emitted light energy pass from pigment system and ultimately trapped by the special pigment known as trapping centre.
Dark Reaction
Reducing capacity of NADPH and the energy of ATP are utilised in the conversion of carbon dioxide to carbohydrates.
ATP and NADPH produced during light reaction are utilised in dark reaction to reduce carbon dioxide to carbohydrates by a process called carbon fixation. It occurs in stroma . The process comprises a series of reaction and is called Calvin cycle. The whole reaction have 3 parts.
(a) Carboxylation
(b) Glycolytic reversal
(c) Regeneration of RuBP
1. Light Reaction
2. Dark Reaction
Light Reaction
Solar energy is trapped by chlorophyll and stored in the form of chemical energy (ATP) and as reducing power (NADPH).
This photochemical reaction is also known as Hill reaction in which water splits by the excited pigments in presence of sunlight resulting in release of oxygen, hydrogen & electron. These electrons carried by a number of electron carriers and ultimately accepted by NADP. Also accepting proton, NADP gets reduced to NADPH2 which is highly reducing substance that reduces carbon dioxide during dark reaction. During flow of electrons some amount of energy is released which couples ADP and inorganic phosphate into ATP by the process known as photophosphorylation.
Thylakoids perform the light reaction as they possess both pigments system and ATPase of light energy falls on pigment molecule , they become excited and exit light energy. All these emitted light energy pass from pigment system and ultimately trapped by the special pigment known as trapping centre.
Dark Reaction
Reducing capacity of NADPH and the energy of ATP are utilised in the conversion of carbon dioxide to carbohydrates.
ATP and NADPH produced during light reaction are utilised in dark reaction to reduce carbon dioxide to carbohydrates by a process called carbon fixation. It occurs in stroma . The process comprises a series of reaction and is called Calvin cycle. The whole reaction have 3 parts.
(a) Carboxylation
(b) Glycolytic reversal
(c) Regeneration of RuBP
Ncy concept
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