Cytoplasm

The cytoplasm is the material that fills a cell between the plasma membrane and, in eukaryotes, the nuclear envelope. It has two parts: the cytosol, a thick watery gel, and everything held within it, including organelles such as mitochondria and the endoplasmic reticulum, the protein fibers of the cytoskeleton, and ribosomes. Bacteria and archaea have no nucleus, so their cytoplasm takes up the whole interior and also contains the cell's DNA, gathered in a region called the nucleoid.

Although it is mostly water, the cytoplasm feels semi-solid because it is crowded with proteins. Sugars, amino acids, nucleotides, fatty acids and ions such as potassium and sodium are dissolved in it, and many of the cell's chemical reactions happen there, including glycolysis and the making of proteins on free ribosomes. The cytoskeleton gives the cytoplasm structure and carries organelles and vesicles from place to place, and in many plant cells the cytoplasm visibly streams around the central vacuole.

Students often mix up cytoplasm and cytosol. The cytosol is only the fluid, while the cytoplasm includes the organelles floating in it. The comparable material inside the nucleus has its own name, nucleoplasm.