organeller

Organeller (organelles in English) are specialized subcellular structures within eukaryotic cells that perform defined functions essential for cellular life. They are mostly enclosed by lipid membranes, creating distinct internal environments, although some structures, such as ribosomes, are not membrane-bound. The nucleus houses genetic material and coordinates gene expression; the nuclear envelope contains pores that regulate traffic with the cytoplasm. Mitochondria generate most cellular ATP through respiration and house their own circular DNA and ribosomes. In plant and algal cells, chloroplasts capture light energy and carry out photosynthesis, and they also contain their own DNA.

The endoplasmic reticulum manufactures proteins and lipids; ribosomes studded on the rough ER synthesize proteins destined for secretion or membranes, while the smooth ER is involved in lipid synthesis and detoxification. The Golgi apparatus processes and sorts proteins and lipids for delivery to different destinations. Lysosomes and, in plant and fungal cells, vacuoles store substances and degrade macromolecules; lysosomal enzymes recycle cellular components via autophagy. Peroxisomes break down fatty acids and detoxify reactive molecules. Vesicles and endosomes mediate transport within the cell and between compartments.

Many organeller, notably mitochondria and chloroplasts, are believed to have originated from ancestral bacteria through endosymbiosis, as they contain their own DNA and ribosomes and replicate independently. The term encompasses a broad set of structures that enable compartmentalization, metabolism, signaling, and the maintenance of cellular homeostasis.