Chloroplasts are small, green, discoid or ellipsoid cytoplasmic organelles (plastids) of green plants. It is 4-6µ in length and 1-2µ in thickness and is bounded by two unit membranes (each of 40-60Å thick) and consisting of lipid and protein. The space enclosed by them is approximate 300Å. Internally the chloroplast is filled with a hydrophilic matrix called as stroma in which grana are embedded. Each granum consists of 5-25 disk shaped granum lamellae or thylakoids placed one above the other like the stack of coins. Some of the grana lamellae are connected with the grana lamellae of other granum by somewhat thinner stroma lamellae. The photosynthetic pigments are confined to grana. The stroma is aqueous and contains enzymes and minerals.
•Light reaction of photosynthesis takes place in grana and dark reaction takes place in the stroma.
• Synthesis of starch, protein and fatty acids also takes place in the chloroplast.
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