Page 22 - EM BIOLOGY NOTES 10TH CLASS PSR DIGITAL BOOKS

T.S. OF CHLOROPLAST (TRANSVERSE SECTION OF CHLOROPLAST)

 Chlorophyll contains Mg. Chlorophyll means green leaf.
 Chlorophyll A - Blue - green in colour. Chlorophyll B - Yellow - green in colour.
Chloroplast Chlorophyll
1. It is an organelle present in plant cell. 1. It is a pigment present in chloroplast.
2. It is green in colour due to the presence 2. It is green in colour due to it reflects
of chlorophyll. the green light of the sunlight.
3. It is responsible for photosynthesis. 3. It is responsible for trapping the light
for photosynthesis.
4. The entire process of photosynthesis 4. The process of photosynthesis starts
occurs in chloroplast. with the help of cholorophyll.
 The upper surface of the leaf more greeny and shiny than the lower surface, because ...
 Upper surface of the leaves contains palisade parenchyma while lower surface contains
spongy parenchyma.
 Palisade parenchyma contains more chloroplasts than spongy parenchyma.
 Chloroplasts are green in colour due to the presense of chlorophyll. Chlorophyll reflects
the green light.
 Due to this reason, the upper surface of the leaf more greeny and shiny than the lower
surface.
Process of Photosynthesis

There are two major phases are found in photosynthesis.
The are : 1. Light reactions / photo chemical reactions
2. Dark reactions / Light independent reactions.
1. Light reactions : (Photo chemical phase)
 Some reactions of photosynthesis that occurs only in the presense of light are called Light
reactions.
 During this phase light energy converted into chemical energy. i.e., ATP and NADPH. So,
this phase is technically called as Photochemical phase.
 This phase of reactions takes place in the Grana of the chloroplast.
 Light reactions occur in several steps :
Step - I : When the light falls on the chlorophyll, it becomes activated by absorbing photons.
Step - II : Photolysis / Hill reaction
 This energy is used in splitting the water molecule into ions.

 H O  H  OH 
2
 This reaction is known as photolysis, which means splitting by light. It is discovered by the
scientist Hill. Hence, it is called as Hill’s reaction.

Step - III : The highly reactive ions H OH,   of water undergoes quick changes in two
different directions.

)
 OH ions produce water (H O and O through a series of steps.
2 2

d
 H ions undergo series of changes and formed ATP and NADPH. These are also called
assimilatory powers.
 The end products of light reactions are O , ATP and NADPH.
2

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