Cytoplasm

The cell is filled with a ground substance called the cytoplasmic matrix, or cytosol. This colloidal, jelly-like material is not static -- it shows a streaming movement within the cell known as cyclosis. The cytoplasm's major component is water, along with a mix of organic and inorganic molecules such as sugars, amino acids, vitamins, enzymes, nucleotides, minerals, and waste products.

The cytoplasm also houses the cell's various organelles -- the endoplasmic reticulum, Golgi complex, mitochondria, plastids, nucleus, microbodies, and cytoskeletal elements such as microtubules. It acts both as a source of raw materials for the cell's activities and as the seat where many of the cell's metabolic reactions actually take place, and it helps distribute and exchange materials between the different organelles.

Cell organelles themselves are best thought of as compartments within the cell, each carrying out a specific function; some of them coordinate with one another to complete particular tasks. The nuclear membrane, endoplasmic reticulum, Golgi complex, lysosomes, and the various vesicles and vacuoles form one such coordinated group, together considered the endomembrane system of the cell, while organelles with their own distinct, self-contained functions -- such as mitochondria or chloroplasts, which carry out specific kinds of energy conversion -- are not included in that group. …