Whats the purpose of an endoplasmic reticulum

The endoplasmic reticulum can either be smooth or rough, and in general its function is to produce proteins for the rest of the cell to function. The rough endoplasmic reticulum has on it ribosomes, which are small, round organelles whose function it is to make those proteins.

meteorologists would compare a new weather map with one 24 h old to see how fast a front is moving.