Aug 21, 2010

Photosynthesis (SPM level)

Photosynthesis – takes place in the chloroplast.
Light reaction (occurs in grana; splitting up water molecules – photolysis of water)
Dark reaction (occurs in stroma; fixation of carbon dioxide)

Light reaction - occurs in the grana (contained chlorophyll) - takes place in the presence of sunlight and chlorophyll - chlorophyll absorbs light; then it becomes activated and this energy is used to :
i) produce energy in the form of – ATP (used for dark reaction)
ii) split up water molecules (photolysis) into hydroxyl ions(OH-) and hydrogen ions (H+) - oxygen is released; but hydrogen enters dark reaction.

Dark reaction (Light independent reaction) - takes place in the stroma -ATP combined with hydrogen atoms (from the light reaction) are used to reduce carbon dioxide to form glucose.

Glucose produced –
i) converted to starch (stored),
ii) transformed - sucrose ; transported to other parts
iii) synthesis of cellulose
iv) converted to a. acids and fatty acids.