organelle
(OR-guh-NEL)
A small structure in a cell that is surrounded by a membrane and has a specific function. Examples of organelles are the nucleus (a structure that contains the cell’s chromosomes and is where RNA is made), mitochondria (structures that make energy for the cell), and lysosomes (sac-like containers filled with enzymes that digest and help recycle molecules in the cell).
Enlarge this image in new windowParts of a cell. A cell is surrounded by a membrane, which has receptors on the surface. A cell has several small structures inside it, including the nucleus, mitochondria, endoplasmic reticulum, and Golgi complex. These all have specific functions in the cell.