Why is smooth endoplasmic reticulum shaped different than rough?

Question

smooth endoplasmic reticulum is composed of tubules while rough endoplasmic reticulum are flat sheets. Why?

Answer 1

There are ribosomes attached to it.

Answer 2

Hi again. if you really want to know the gory details i can tell you... tubule form because there are proteins that help shape the high curvature in the ER membrane. These proteins are called DP1 and Reticulon 4A/NoGoA and then atleast some other proteins that play a role which are not identified yet. DP1 and reticulons form a hairpin structure that inserts in the outer leaflet of the ER membrane causing the curvature. these proteins are not found on the flat sheets of the rough ER and therefore they do cause the characteristic curvature. for more info read the link in sources.