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Illustration of a eukaryotic cell membrane Comparison of a eukaryotic vs. a prokaryotic cell membrane. The cell membrane (also known as the plasma membrane or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of a cell from the outside environment (the extracellular space).
For example, the membrane around peroxisomes shields the rest of the cell from peroxides, chemicals that can be toxic to the cell, and the cell membrane separates a cell from its surrounding medium. Peroxisomes are one form of vacuole found in the cell that contain by-products of chemical reactions within the cell.
All of these sub-cellular compartments are surrounded by one or more lipid bilayers and, together, typically comprise the majority of the bilayer area present in the cell. In liver hepatocytes for example, the plasma membrane accounts for only two percent of the total bilayer area of the cell, whereas the endoplasmic reticulum contains more ...
A phospholipid bilayer is an example of a biological semipermeable membrane. It consists of two parallel, opposite-facing layers of uniformly arranged phospholipids. Each phospholipid is made of one phosphate head and two fatty acid tails. [3] The plasma membrane that surrounds all biological cells is an example of a phospholipid bilayer. [2]
For example, in human erythrocytes the cytosolic side (the side facing the cytosol) of the plasma membrane consists mainly of phosphatidylethanolamine, phosphatidylserine, and phosphatidylinositol. By contrast, the exoplasmic side (the side on the exterior of the cell) consists mainly of phosphatidylcholine and sphingomyelin , a type of ...
Membrane proteins fall into several broad categories depending on their location. Integral membrane proteins are a permanent part of a cell membrane and can either penetrate the membrane (transmembrane) or associate with one or the other side of a membrane (integral monotopic).
Membrane lipids are a group of compounds (structurally similar to fats and oils) which form the lipid bilayer of the cell membrane. The three major classes of membrane lipids are phospholipids, glycolipids, and cholesterol. Lipids are amphiphilic: they have one end that is soluble in water ('polar') and an ending that is soluble in fat ...
The membrane is represented in light yellow. A transmembrane protein is a type of integral membrane protein that spans the entirety of the cell membrane. Many transmembrane proteins function as gateways to permit the transport of specific substances across the membrane.