Eukaryotes are organisms composed of cells that have their genetic material surrounded a nuclear membrane, the nucleus, as well as a number of other membrane-bound organelles that carry out cellular functions.
The eukaryotic cell's endomembrane system is a network of organelles (like little organs) involved in manufacturing and material transport, allowing the cell to make, move and break down cellular products.
Article Summary: A cell's endomembrane system consists of the rough and smooth endoplasmic reticulum, Golgi apparatus, vesicles and plasma membrane, all working together to transport cellular materials.
Endomembrane System of Eukaryotic Cells
Portions of this article originally appeared on Suite101 online magazine.
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The plasma membrane is the structure separating the inside from the outside of the cell. It consists of a phospholipid bilayer, a double membrane composed of a unique type of lipid that spontaneously organizes into two layers. The plasma membrane controls traffic of materials into and out of the cell.
Rough Endoplasmic Reticulum
Folding out of the nuclear envelope, the rough ER is a network of continuous sacs, studded with ribosomes. The rough ER manufactures, processes, and prepares proteins for transport.
Smooth Endoplasmic Reticulum
Similar in appearance to rough ER, the smooth endoplasmic reticulum is also a network of continuous sacs, but without ribosomes attached. This organelle is involved in the production of lipids, further processing of proteins, carbohydrate metabolism, and detoxification of drugs and poisons.
The Golgi apparatus modifies the proteins and lipids made by the endoplasmic reticulum and prepares these materials for export from the cell. This organelle also encloses digestive enzymes into membranes to form vesicles called lysosomes.
Vesicles are relatively small, enclosed compartments that have budded off from other parts of the endomembrane system. The contents of a vesicle are separated from the cytosol (internal fluid of the cell) by at least one lipid bilayer. Vesicles are like the trucks of the endomembrane system. They function to store, transport, or digest cellular products and waste.
Many vesicles are made by the Golgi apparatus, the endoplasmic reticulum, or parts of the plasma membrane. Vesicles made from the plasma membrane form when the cell takes in (endocytosis) or discharges (exocytosis) materials.
If vesicles are the trucks of the endomembrane system, lysosomes are specifically the garbage (or recycling) trucks. These single membrane bound structures contain digestive enzymes that break down cellular waste, debris and nutrients for use by the cell. They are the sites of cellular digestion.
Sources and Helpful Cell Biology Links
Bauman, R. (2005) Microbiology.
Park Talaro, K. (2008) Foundations in Microbiology.
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Watching the movement of colored wax blobs in a lava lamp is an excellent way to help students understand how organelles of the
The endomembrane system consists of the nuclear envelope, rough and smooth endoplasmic reticulum (ER), the Golgi apparatus as well as the cell's plasma membrane, and includes the vesicles that bud off these membranes for intracellular transport (moving stuff around inside the cell), exocytosis (stuff leaving the cell) and endocytosis (stuff coming into the cell).