Page 16 - E-Biology Sec.2 2024-2025 U1_Handy
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A)Chloroplast (Green plastid) structure:
It appears as homogeneous mass with a convex lens under light microscope
to collect large amount of light.
It consists of:
1- Double thin external membrane:
It is 10 nm thickness.
2- Matrix (Stroma) consists of colorless protein.
3- Starch granules:
They spread with large no. in the stroma.
They are small in size as they’ll change back into soluble sugar
translocated to other organs.
4- Grana:
They are disc-shaped arranged along of the plastid in the stroma
and linked together by thin membranes.
Granum diameter is 0.5 µm and its thickness is 0.7 µm.
Granum consists of 15 / more hollow discs are arranged above each
other, the margins of discs of a granum may extend to meet the margins
of discs of other granum to increase the surface area of grana to absorb
the light.
They are carrying the pigments that absorb the light.
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First Term
