THE BEECHMONT CREST GUIDE TO BIOLOGICAL TERMS
ENDOPLASMIC RETICULUM
The endoplasmic reticulum is the largest membrane inside a eukaryotic cell. It consists of lipid bilayers, which contain embedded proteins.
The endoplasmic reticulum (ER) is actually a network of membranes within the cell. Its primary functions are protein and lipid synthesis.
The endoplasmic reticulum is generally divided into two major sections: the rough endoplasmic reticulum and the smooth endoplasmic reticulum.
The rough endoplasmic reticulum contains many ribosomes, giving it a “rough” appearance under the microscope. Proteins are synthesized on the rough portion of the ER, which are eventually exported out of the cell.
The smooth endoplasmic reticulum has few ribosomes. However, the smooth ER does contain numerous enzymes, which are used in the synthesis of carbohydrates and lipids.
Cells that perform a lot of lipid synthesis (those of the intestines, for example) have large smooth ERs.