Cytoplasm

The term cytoplasm refers to the contents of a cell, excluding its nucleus. More specifically, cytoplasm refers to the jelly-like or semisolid fluid that is enclosed by the cell's plasma membrane. Before scientists had knowledge of what was contained in a eukaryotic cell (one with a nucleus and an outer membrane), the term cytoplasm was a convenient description for the cell's contents. Now it is known that cytoplasm contains the cell's organelles—the many tiny structures that each have a particular function to perform. The cytoplasm, along with the nucleus, make up what is called the protoplasm, or living material of a cell.

Cytoplasm is the fluid environment in which the cell's metabolism (the chemical processes that make a cell a living thing) takes place. Cytoplasm is a gel-like fluid rich in proteins, fats, carbohydrates, salts, and other chemicals. Unlike a common gelatin, however, cytoplasm is constantly moving and transporting materials from one place to another. This cytoplasmic movement can best be observed in slime molds, amoeba (uh-MEE-buh), and certain species of algae, in which an ordinary light microscope will reveal what appear to be streams of cytoplasm coursing through the interior of a cell.

In addition to these proteins and enzymes in fluid form, the cytoplasm contains a wide variety of organelles. Each of these tiny structures carries out a particular task that is important in maintaining the life of the cell. Some break down food while others move waste around and get it ready to be expelled. Others may store important materials. All organelles in the cytoplasm are surrounded by membranes. Some of the more important organelles found in a cell's cytoplasm are mitochondria (energy generators), ribosomes (assembly units for proteins), endoplasmic reticulum (material transporters), Golgi bodies (storage), and other components like the cell's coded plans and instructions that are carried in its ribonucleic acid (RNA). Plant cells have chloroplasts in their cytoplasm, enabling them to convert sunlight into food. Although animal cells do not have chloroplasts, they do have lysosomes which enable them to digest the food they take in.

[See alsoCell ]

cy·to·plasm / ˈsītəˌplazəm/ • n. Biol. the material or protoplasm within a living cell, excluding the nucleus.DERIVATIVES: cy·to·plas·mic / ˌsītəˈplazmik/ adj.

cytoplasm The material surrounding the nucleus of a cell. It consists of a matrix (see cytosol) in which the cell's organelles are suspended. The cytoplasm may be differentiated into dense outer ectoplasm, which is concerned primarily with cell movement, and less dense endoplasm, which contains most of the cell's structures.

cytoplasm Jelly-like matter inside a cell and surrounding the nucleus. Cytoplasm has a complex constituency and contains various bodies known as organelles, with specific metabolic functions. The proteins needed for cell growth and repair are produced in the cytoplasm.

cytoplasm The part of a cell that is enclosed by the plasma membrane, but excluding the nucleus.