membrane

Definition

Target type: cellularcomponent

A lipid bilayer along with all the proteins and protein complexes embedded in it and attached to it. [GOC:dos, GOC:mah, ISBN:0815316194]

The cell membrane, also known as the plasma membrane, is a vital structure that encloses the cell and regulates the passage of molecules in and out. It is a phospholipid bilayer, meaning it consists of two layers of phospholipid molecules arranged with their hydrophilic (water-loving) heads facing the exterior and interior of the cell, and their hydrophobic (water-fearing) tails facing each other in the interior of the membrane. Embedded within this bilayer are various proteins that serve different functions, including transport, signaling, and adhesion.

The membrane is not a static structure but rather a dynamic fluid mosaic, with its components constantly moving and interacting.

Here are some of the key cellular components of the membrane:

* **Phospholipids:** These are the primary building blocks of the membrane. They consist of a glycerol molecule linked to a phosphate group (hydrophilic head) and two fatty acid chains (hydrophobic tails). The phospholipid bilayer acts as a barrier, preventing the free passage of most water-soluble molecules while allowing small, non-polar molecules to pass through.
* **Proteins:** Proteins are embedded within the phospholipid bilayer, performing various functions. Some proteins act as channels or carriers to facilitate the transport of molecules across the membrane. Others act as receptors that bind to signaling molecules, initiating intracellular signaling pathways. Still, other proteins serve as enzymes, catalyzing reactions within the membrane.
* **Cholesterol:** Cholesterol is a type of lipid found within the membrane. It helps to maintain the fluidity and integrity of the membrane by preventing it from becoming too rigid or too fluid.
* **Glycolipids and Glycoproteins:** These molecules are formed by the attachment of carbohydrates to lipids or proteins, respectively. They play important roles in cell recognition and signaling.
* **Cytoskeleton:** The cytoskeleton is a network of protein filaments that provides structural support to the cell. It is also involved in cell movement and division. The cytoskeleton interacts with the membrane, helping to maintain its shape and stability.
* **Extracellular Matrix:** The extracellular matrix (ECM) is a complex network of molecules that surrounds cells. It provides structural support and regulates cell behavior. The ECM interacts with the membrane through specialized proteins called integrins, which anchor the membrane to the matrix.

The membrane is a highly complex structure that plays a crucial role in the life of the cell. Its diverse components work together to regulate the passage of molecules, facilitate cell communication, and maintain the cell's shape and integrity.'
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Proteins (750)

Compounds (9,146)