Organelle

From EvoWiki

Organelle as its suffix intimates is a term used to describe the 'little' organs within cells. By analogy to the role of organs within the body, organelles are discrete structures within cells that perform specific functions and that are encapsulated by phospholipoprotein membranes. For example, the rough endoplasmic reticulum (RER) is the organelle where messenger RNA is translated into proteins by the ribsosomes attached to the RER. Smooth endoplasmic reticulum (SER) and the Golgi body are organelles which are involved in the post translational processing of proteins. Organelles are a feature of eukaryotic cells and the debate as to origin of such functional compartmentalization is a controversial part of evolutionary theory. For example, mitochondria are organelles which harness energy in the form of ATP. However, uniquely among organelles, they contain their own DNA and one suggestion as to their origin is that early bacteria were subsumed inside the cells of another. The nucleus is also an organelle.