Endoplasmic Reticulum (ER)
- It is a network of membranes that form flattened interconnected sacs called as Cisternae are tubular in structure, and form a three-dimensional polygonal network.
- They are frequently associated with ribosomes and special proteins called translocons that are necessary for protein translation within the RER.
- The phospholipid membrane encloses a space, the lumen from the cytosol, which is continuous with the perinuclear space.
- The surface of the rough endoplasmic reticulum is studded with the protein manufacturing ribosome, which gives it a rough appearance. Hence it is referred as a rough endoplasmic reticulum.
- The smooth endoplasmic reticulum consists of tubules, which are located near the cell periphery. This network increases the surface area for the storage of key enzymes and the products of these enzymes.
- Rough endoplasmic reticulum synthesizes proteins, while smooth endoplasmic reticulum synthesizes lipids and steroids. It also metabolizes carbohydrates and regulates calcium concentration, drug detoxification, and attachment of receptors on cell membrane proteins.
- Endoplasmic reticulum varies extensive extending from the cell membrane through the cytoplasm and forming a continuous connection with the nuclear envelope.
- They play a vital role in the synthesis of proteins, lipids, glycogen and other steroids like cholesterol, progesterone, testosterone, etc.
- They provide the increased surface area for cellular reactions.
- They help in the formation of nuclear membrane during cell division.
- They play a vital role in the formation of the skeletal framework.
Figure 4- Endoplasmic Reticulum