Some well-arranged cisterns of RER of a regular shape #1, #2 with ribosomes gradiently change into smooth endoplasmic reticulum #1, #2, #3 with no ribosomes. In liver cells (hepatocytes) and some other cells, such cisterns of SER are actually forming a quite peculiar, irregular labyrinth that occupies a considerably large space in the cytoplasm. The SER membranes make up 10-15% of all membranes in hepatocytes. The SER prevails in cells that synthesize steroid hormones (adrenal cortex; gonadal cells). In hepatocytes, the SER is well-developed near the biliary poles of cells because the organelle is the main bile-producing machinery. This is also the site for bilirubin transformation from toxic into non-toxic conjugated form. The latter is excreted by the bile. The liver SER is its principal organelle to exert the function of detoxication.

Very-low-density lipoproteins (VLDL), which transport cholesterol and other lipids, are produced in both RER (protein component) and SER (lipids). Functional connection between the SER and granules of glycogen #1, #2, #3 is emphasized by their proximity; the SER participates in the metabolism of this polysaccharide. Glycogen is also the main source for energy production in the mitochondria #1, #2.