Photosynthesis is the process by which green plants manufacture food.Photosynthesis takes place in two stages; the light and dark stages.
The light stage which occurs in the presence of light involves:
energization of the chlorophyll;the chlorophyll traps, absorbs and captures light energy.
photolysis of water;the energized chlorophyll supplies energy to split the water molecules into hydrogen ion and hydroxyl ion.
The hydroxyl ion is reconverted to water and oxygen is given out as a by product.
The hydrogen is accepted by a co-enzyme (NADP).
The energy not used in the photolysis is released to ADP to form ATP which is used in the dark reaction.
The dark stage which occurs in the absence of light involves the reduction of carbon dioxide with the hydrogen provided by the NADP to form sugar.
N:B. All reactions that take place in the light stage occur in the grana in the chloroplast while those of the dark stage occur in the stroma in the chloroplast.