The endoplasmic reticulum performs several functions in the cell including:

• Production and synthesis of proteins
• Transportation of proteins to another organelle such as the Golgi apparatus, plasma membrane or lysosomes
• Formation of nuclear membrane during cell division
• Synthesis of lipids, glycogen and steroids such as progesterone and testosterone
• Increasing surface area for cellular reactions

There are two types of endoplasmic reticulum – smooth and rough. Both have slightly different function. The smooth endoplasmic reticulum is responsible for:

• Synthesis of essential lipids such as cholesterol and phospholipids
• Maintenance of calcium homeostasis
• Metabolism of carbohydrates
• Production and secretion of steroid hormones

The rough endoplasmic reticulum is responsible for:

• Synthesis of proteins and enzymes
• Protein folding
• Protein sorting – Quality control
• Formation of lysosomes