Principles of Biochemistry

1.1.3.2 Cytoplasm

The cytoplasm is the part of a cell that is enclosed within the cell membrane. In the cells of prokaryote organisms, which lack a nucleus, the contents of are contained within the cytoplasm. In the cells of eukaryote organisms the contents of the cell nucleus are separated from the cytoplasm, and are there called the nucleoplasm.

The cytoplasm contains organelles, which are filled with liquid that is kept separate from the rest of the cytoplasm by biological membranes. It is within the cytoplasm that most cellular activities occur, such as many metabolic pathways including glycolysis, and processes such as cell division. The inner, granular mass is called the endoplasm and the outer, clear and glassy layer is called the ectoplasm.

The part of the cytoplasm that is not held within organelles is called the cytosol. The cytosol is a complex mixture of cytoskeleton filaments, dissolved molecules, and water that fills much of the volume of a cell.