Early cytologists believed that the interior of the living cell was filled with a homogeneous and viscous fluid, into which the core was plunged.
This fluid was named cytoplasm (from the Greek kytos, cell, and plasma, what shapes, shapes).
It is now known that the space between the plasma membrane and the nucleus is quite different than those pioneer cytologists imagined. In addition to the fluid part, the cytoplasm contains membranous pouches and channels and cytoplasmic organelles or organelles, which perform specific functions in eukaryotic cell metabolism.
Cytoplasmic fluid is mainly composed of water, proteins, minerals and sugars. In cytosol, most of the vital chemical reactions occur, including the fabrication of molecules that will make up the cellular structures. It is also in cytosol that many animal cell reserve substances, such as fats and glycogen, are stored.
On the periphery of the cytoplasm, cytosol is more viscous, having a soft gelatin consistency. This region is called ectoplasm (from the Greek, ectos, outside). In the most central part of the cell is the endoplasm (from the Greek, endos, inside), of more fluid consistency.
Cytosol is in continuous motion, driven by the rhythmic contraction of certain strands of protein present in the cytoplasm, in a process similar to what makes our muscles move. Cytosol flows constitute what biologists call cyclose. In some cells, cyclosis is so intense that there are true internal circulatory currents. Its speed increases with increasing temperature and decreases at low temperatures as well as lack of oxygen.