what are events occur during photosynthesis?
The process of photosynthesis occurs in two phases – the light reactions and the dark reactions.
Light reactions – As the name suggests, this reaction takes place in the presence of light. Light energy is absorbed by chlorophyll molecules and is utilized for splitting water molecules into hydrogen and oxygen. Additionally in this phase, assimilatory power in the form of ATP and NADPH2 are produced.
Light reactions occur in the membranes of thylakoids.
Events occurring during light reactions:
Absorption of light energy by chlorophyll molecules
Splitting of water molecules into hydrogen and oxygen atoms
Formation of ATP and NADPH2
Dark reactions – This reaction does not require direct light and occurs in the stroma of chloroplasts. During this phase, ATP and NADPH2 (formed during light reactions) are utilized for the reduction of CO2 to carbohydrates (food).
Event occurring during dark reaction:
Reduction of CO2 to form carbohydrates
THE MAIN EVENTS OF PHOTOSYNTHESIS
1. Light is absorbed by the leaf’s chloroplasts.
2. The light energy is used to split water molecules.
3. The break up of water releases oxygen, electrons and protons (H+, H ions)
a. The electrons go to the chlorophyll.
b. The protons are stored in the chloroplast.
c. The oxygen passes from the chloroplast. Some will be used by the mitochondria for aerobic respiration and the remainder will be passed into the atmosphere.
4. Some of the light energy is carried to the chlorophyll to form high energy electrons.
5. The high energy electrons and the stored protons combine with carbon dioxide to form glucose. (C6H12O6)
This diagram represents the 5 events listed above: