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Cells are called as the fundamental component of life. The development of Cell Theory is credited to three scientists namely Theodor Schwann, Matthias Schleiden and Rudolph Virchow. According to cell Theory, every organism is composed of one or more cells and the derivatives of those cells. Each cell carries out life activities, grows, requires energy and attains a limited size. Novel cells arise only from the pre existing cells by the method of cell division. An Organelle in cell biology is one of numerous structures within the cell which has specialized function and is suspended in the cytoplasm.

There are also non membrane bound organelles that are huge assemblage of macromolecules in the cytoplasm that carry out specialized functions. Such cell structures include: cytoskeleton, ribosome, centriole, cilia and flagellum and proteasome.

The cytoskeleton renders support and movement for a cell and its organelles. It is composed of a network of protein filaments, fibers and tubules.

The Animal cell organelles that are not found in plant cell include cilia and flagella. Cilia and flagella are the organelles that are hair like which extend from the surface of several cells of animal. Both the structures are somewhat identical except that flagella are much longer and whip like and cilia are shorter structures. A cell contains usually a few flagella while cilia may be present over the entire cell surface. Flagella and cilia helps for locomotion in single celled organisms and for the movement of substances over cell surfaces in multi-cellular individuals.

Centrioles that are present in animal cells have paired structures near the nucleus that are composed of a cylinder of microtubule pairs that assists in the separation of chromosome pairs during cell division.

The protein complexes that are present within every Eukaryotes, Bacteria and Archaea are termed as proteosomes. They are situated in the nucleus and cytoplasm of the eukaryotes and functions to degrade damaged or unwanted proteins by proteolysis.