Mechanism of Photosynthesis

Light Reaction

Chlorophyll captures light energy
> excites the electron
> electron leave the chlorophyll molecules

Light energy(Photolysis of Water)
> split water molecules into hydrogen/hydroxyl ions
> hydrogen ions combine with electrons(chlorophyll) to form hydrogen atoms
> energy from the excited electron is used to form ATP
> hydroxyl ions loses electron to form hydoxyl group
> hydroxyl group combine to form water/oxygen
> ATP provide energy and hydrogen atoms provide reducing power for dark reaction

Dark Reaction(Calvin Cycle)

> light independent
> hydrogen atom are used to fix carbon dioxide
> Result: reduction of carbon dioxide into glucose
> glucose undergo condensation to form starch

Equation

6 CO₂ + 12 H₂O + light energy --> C₆H₁₂O₆ + 6 O₂ + 6 H₂O

Schematic Diagram

Comparison Light and Dark Reaction 

Light Reaction	Differences	Dark Reaction
Photolytic reaction	Type of reaction	Series of bio-chemical reactions
Day	Time of reaction	Day and night
Grana	Site of reaction	Stroma
Water	Substance required for reaction	Carbon dioxide
Oxygen and water	Products of reaction	Glucose and water
Occurs	Photolysis of water	Does not occur
Required	Light energy	Not required
Forms ATP and hydrogen atoms	ATP and hydrogen atoms	Uses ATP and hydrogen atoms