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granule science definition
- A rock or mineral fragment larger than a sand grain and smaller than a pebble. Granules have a diameter between 2 and 4 mm (0.08 and 0.16 in) and are often rounded.
- Any of the small, transient convective cells within the Sun's photosphere where hot gases rise and quickly dissipate. Granules are generally between a few hundred and 1,500 km in width. They completely cover the Sun's surface, giving it its characteristic grainy or stippled look, and form and break up within a matter of minutes.
- An aggregate of enclosed grainy matter found in a cell. Granulocytes, mast cells and other cells contain granules in their cytoplasm, which differ in size and can often be identified by a characteristic laboratory stain based on their composition. Granules produce and store biologically active substances, the release of which is called degranulation. The granules of granulocytes contain mostly multiple enzymes and other proteins; those of mast cells contain histamine and other chemical mediators.
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