The endoplasmic reticulum is a cell organelle found both in plant and animal cells. The endoplasmic reticulum is of two types based on the basis of presence or absence of ribosomes on its surface. The endoplasmic reticulum having ribosomes on its surface is called the rough endoplasmic reticulum (RER) and the endoplasmic reticulum without ribosomes on its surface is called the smooth endoplasmic reticulum (SER).
The SER is mainly involved in the synthesis of lipids and cholesterol. The SER is present in a high percentage in cells that synthesize lipids such as sebaceous glands, testes, and ovaries.