Microsomes - From where do they arise?

Microsomes are small spherical membranous vesicles with attached ribosomes. They sediment, during differential sedimentation, only in the late stages of a preparation when very high centrifugal velocities are used. They don’t appear in electronmicrographs of a cell. From where do they arise?
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1 Answer

Answer :

Fragments of endoplasmic reticulum are transformed from lipid bilayer sheets, with attached ribosomes, into spherical vesicles. This is a result of the homogenization used in preparing the samples and also the tendency of lipid bilayers to spontaneously reseal. 
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