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In cell biology, an organelle is a specialized subunit, usually within a cell, that has a specific function. The name organelle comes from the idea that these structures are parts of cells, as organs are to the body , hence organelle, the suffix -elle being a diminutive .
Most important among these is a cell nucleus, [2] an organelle that houses the cell's DNA. This nucleus gives the eukaryote its name, which means "true kernel (nucleus)". Some of the other differences are: The plasma membrane resembles that of prokaryotes in function, with minor differences in the setup. Cell walls may or may not be present.
Schematic of the eukaryotic flagellum. 1-axoneme, 2-cell membrane, 3-IFT (Intraflagellar transport), 4-Basal body, 5-Cross section of flagellum, 6-Triplets of microtubules of basal body. Longitudinal section through the flagella area in Chlamydomonas reinhardtii. In the cell apex is the basal body that is the anchoring site for a flagellum.
Some cell types, such as retinal photoreceptor cells, possess highly specialized primary cilia. [ 24 ] Although the primary cilium was discovered in 1898, it was largely ignored for a century and considered a vestigial organelle without important function.
A particular biosynthetic pathway may be located within a single cellular organelle (e.g., mitochondrial fatty acid synthesis pathways), while others involve enzymes that are located across an array of cellular organelles and structures (e.g., the biosynthesis of glycosylated cell surface proteins).
Vesicles can also fuse with other organelles within the cell. A vesicle released from the cell is known as an extracellular vesicle. Vesicles perform a variety of functions. Because it is separated from the cytosol, the inside of the vesicle can be made to be different from the cytosolic environment. For this reason, vesicles are a basic tool ...
Cell surface receptors (membrane receptors, transmembrane receptors) are receptors that are embedded in the plasma membrane of cells. [1] They act in cell signaling by receiving (binding to) extracellular molecules. They are specialized integral membrane proteins that allow communication between the cell and the extracellular space.
The bacterial cell wall differs from that of all other organisms by the presence of peptidoglycan (poly-N-acetylglucosamine and N-acetylmuramic acid), which is located immediately outside of the cytoplasmic membrane. Peptidoglycan is responsible for the rigidity of the bacterial cell wall and for the determination of cell shape. It is ...