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Specialized cells can have a lot of smooth endoplasmic reticulum and in these cells the smooth ER has many functions. [6] It synthesizes lipids, phospholipids, [19] [20] [21] and steroids. Cells which secrete these products, such as those in the testes, ovaries, and sebaceous glands have an abundance of smooth endoplasmic reticulum. [22]
The cells that synthesize these hormones are rich in smooth ER. [24] [27] Liver cells are another example of specialized cells that contain an abundance of smooth ER. These cells provide an example of the role of smooth ER in carbohydrate metabolism. Liver cells store carbohydrates in the form of glycogen.
The ER has two forms: the rough ER, which has ribosomes on its surface that secrete proteins into the ER, and the smooth ER, which lacks ribosomes. [2] The smooth ER plays a role in calcium sequestration and release and also helps in synthesis of lipid.
Smooth endoplasmic reticulum makes hormones and lipids, degrades toxins, and controls cellular levels of calcium. Though most control of cell division is present in the nucleus, the centrosomes present in the endoplasm assist with spindle formation. The endoplasm is the site of many activities necessary for the cell to maintain homeostasis. [2]
The eukaryotic cell cycle consists of four distinct phases: G 1 phase, S phase (synthesis), G 2 phase (collectively known as interphase) and M phase (mitosis and cytokinesis). M phase is itself composed of two tightly coupled processes: mitosis, in which the cell's nucleus divides, and cytokinesis, in which the cell's cytoplasm and cell membrane divides forming two daughter cells.
Cellular compartments in cell biology comprise all of the closed parts within the cytosol of a eukaryotic cell, usually surrounded by a single or double lipid layer membrane. These compartments are often, but not always, defined as membrane-bound organelles. The formation of cellular compartments is called compartmentalization.
The fraction of ER that co-purifies with mitochondria, the so-called Mitochondria-associated endoplasmic reticulum membrane (MAM) has been extensively studied during the last decade. In the " MAM hypothesis " it has been proposed that at the centre of the pathogenesis of Alzheimer's disease resides the disorder of ER-mitochondrial contact sites ...
The ER is an enclosed network of tubules and sacs, and its main functions include protein synthesis, and lipid metabolism. There are 2 types of ER, smooth and rough. The rough ER has ribosomes attached to it used for protein synthesis, while the smooth ER is used more for the processing of toxins and calcium regulation in the cell. [44]