Starch grows through synthesis within plastids (amyloplasts and chloroplasts) in plant cells.
Here's a breakdown of the starch growth process:
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Location: Starch synthesis occurs specifically inside plastids. In photosynthetic tissues like leaves, these are chloroplasts. In non-photosynthetic tissues like roots and storage organs, they are amyloplasts.
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Precursor: The starting point is glucose 1-phosphate.
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Key Enzyme: The enzyme glucose-1-phosphate adenylyltransferase is crucial. It converts glucose 1-phosphate into ADP-glucose.
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ADP-Glucose Formation: ADP-glucose is the immediate precursor that adds glucose units to the growing starch molecule.
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Energy Requirement: The conversion of glucose 1-phosphate to ADP-glucose requires energy, supplied by ATP (adenosine triphosphate).
In simpler terms, imagine starch as a long chain of glucose molecules. To make this chain longer, glucose units, activated by being attached to ADP, are added to the existing starch molecule inside the plastid. This requires energy.
