exterior. The cisternal space is continuous with the perinuclear space. bled into two unequal subunits. The subunits can be separated by their
Structurally, the channel system can be divided into rough or granu- sedimentation coefficients (S) in an ultracentrifuge into larger 60S and
lar endoplasmic reticulum (RER), which has ribosomes attached to its smaller 40S components. These are associated with 73 different pro-
outer, cytosolic surface, and smooth or agranular endoplasmic reticu- teins (40 in the large subunit and 33 in the small), which have structural
lum (SER), which lacks ribosomes. The functions of the endoplasmic and enzymatic functions. Three small, highly convoluted rRNA strands
reticulum vary greatly and include: the synthesis, folding and transport (28S, 5.8S and 5S) make up the large subunit, and one strand (18S) is
of proteins; synthesis and transport of phospholipids and steroids; and in the small subunit.