Derrick has taught biology and chemistry at both the high school and college level. He has a master's degree in science education.
Definition of Endoplasmic Reticulum
Have you ever worked in or visited a large factory? If so, you probably noticed that the largest and most important area of the factory is the production space where the products are assembled. In a cell, this production space is the surface of the endoplasmic reticulum. This is where numerous chemical reactions and processes take place. Without it, production would be closed down, and the cell factory would be out of business.
Cells have many organelles that work together to help them complete their life functions. One of those organelles is the endoplasmic reticulum, which is an interconnected network of membranes used to make proteins, steroids, and lipids located near the nucleus. The surface of the endoplasmic reticulum is basically a workspace for the cell. To maximize the amount of surface area that is available the membranes are folded tightly, rather than being one flat surface.
The endoplasmic reticulum is composed of sac-like structures called cisternae that are folded and bound together. There are two types of endoplasmic reticulum: smooth endoplasmic reticulum, which has a smooth folded surface, and rough endoplasmic reticulum which has a surface studded with ribosomes, making it appear bumpy.
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Smooth Endoplasmic Reticulum
The smooth endoplasmic reticulum is a site for the creation of lipids, phospholipids, and steroids. Cells that secrete these products - such as cells in the testes, ovaries, and skin glands - have a lot of smooth endoplasmic reticulum. Smooth endoplasmic reticulum is also a site for the metabolism of carbohydrates, and in muscle cells it regulates the concentration of calcium. As you can imagine, if the endoplasmic reticulum was just one flat surface, there would not be a lot of area for these processes to take place. This is why the endoplasmic reticulum is made of a highly folded network of membranes to allow for more area.
Rough Endoplasmic Reticulum
The majority of our life processes depend on proteins. Proteins function because of their shape. They have to be specifically folded into a certain shape to fit where they belong and do their jobs. It helps to think of a protein like a key - it must be made just right to fit into a lock.
Ribosomes are responsible for correctly folding proteins. This makes the rough endoplasmic reticulum extremely important, as it has ribosomes covering its surface and provides a space for the proteins to be made. Once the proteins are formed, they are packed into a vesicle (like a little cell taxi) and shipped through the endoplasmic reticulum to the organelle known as the Golgi apparatus to be modified for final use.
The endoplasmic reticulum is a series of folded vesicles that provide a surface for many cellular activities, including the metabolism of carbohydrates and protein production in ribosomes. There are two types of endoplasmic reticulum, the smooth endoplasmic reticulum and the rough endoplasmic reticulum. The smooth endoplasmic reticulum is used in the storage and production of steroids and lipids; the rough, in the production and transport of proteins.
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Endoplasmic Reticulum: Definition & Functions
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