Present by: FOO LI XUAN

LIEW CAI JUAN

YAP AI PING

LOW SHUN EN

THE MECHANISM OF PHOTOSYNTHESIS

Chloroplast - Organelle where photosynthesis takes place

*Chloroplast Structure* Grana - site of light reaction

(singular, granum) - contain the light-trapping pigment chloroplast

* Stroma - site of dark reaction

-the enzymes responsible for the dark reaction of

photosynthesis are found here

* Starch grains- acts as a temporary storage place for products of

photosynthesis

MECHANISMS OF PHOTOSYNTHESIS

*LIGHT REACTION*Chlorophyll absorbs light energy

*This light energy is used to split water molecules in the chloroplast into hydrogen ions and hydroxyl ions. This process is called photolysis of water

*The light reaction also raises the energy level of the chlorophyll and causes some excited electrons to leave the chlorophyll

*Hydrogen ions receive the electrons from the chlorophyll and form hydrogen atoms .The energy released from the excited electrons is used to form ATP

*The hydrogen atoms will enter the dark reaction to combine with carbon dioxide to become carbohydrates

*LIGHT REACTION *The hydrogen atoms will enter the dark reaction to combine with carbon

dioxide to become carbohydrates

*Then, hydroxyl ions release its electrons to the chlorophyll to neutralize them

*The hydroxyl group formed then combine to form water and oxygen

*Oxygen is released into the atmosphere

*DARK REACTION1. In the dark reaction, carbon dioxide which has diffused into

leaves combines with hydrogen from the light reaction .After a series of reaction catalyzed by enzymes, glucose is formed. The energy needed for this process is provided by ATP, which is formed during the light reaction

2. Combining all the equations above into a single equation , we get

24H2O + 6CO2 C6H12O6 + 18H2O +6O2

*Similarities & Differences

Light reaction Dark reaction

Differences

Similarities

*PHOTOSYNTHESIS

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