membrane-bounded organelle

Definition

Target type: cellularcomponent

Organized structure of distinctive morphology and function, bounded by a single or double lipid bilayer membrane. Includes the nucleus, mitochondria, plastids, vacuoles, and vesicles. Excludes the plasma membrane. [GOC:go_curators]

Membrane-bounded organelles are structures within eukaryotic cells that are enclosed by one or more phospholipid bilayer membranes. These membranes serve as selective barriers, regulating the passage of molecules in and out of the organelle. The cellular component of membrane-bounded organelles can be divided into three primary parts: the membrane itself, the enclosed lumen or internal space, and the associated proteins.

The membrane is composed of a phospholipid bilayer, which is a double layer of phospholipid molecules. Each phospholipid molecule has a hydrophilic head that faces the aqueous environment inside and outside the organelle, and a hydrophobic tail that points towards the interior of the membrane. This arrangement creates a barrier that is impermeable to most polar molecules, but allows for the passage of small, nonpolar molecules.

The lumen is the internal space enclosed by the membrane. The composition and function of the lumen vary depending on the specific organelle. For example, the lumen of the endoplasmic reticulum (ER) is involved in protein folding and modification, while the lumen of the Golgi apparatus is involved in the sorting and packaging of proteins.

Associated proteins are embedded within the membrane or attached to its surface. These proteins play a variety of roles in the function of the organelle. Some proteins serve as channels or transporters, facilitating the movement of molecules across the membrane. Others act as enzymes, catalyzing specific biochemical reactions within the organelle. Still others play structural roles, helping to maintain the shape and integrity of the organelle.'
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Proteins (1)

Compounds (3)