Cytoplasm is the colloidal, semi-fluid matter contained within the cell's plasma membrane, in which organelles are suspended. In contrast to the protoplasm, the cytoplasm does not include the cell nucleus, the interior of which is made up of nucleoplasm.
The aqueous component of the cytoplasm (making up 80 percent of it) is composed of ions and soluble macromolecules like enzymes, carbohydrates, different salts and proteins, as well as a great proportion of ARN. The cytoplasm's watery component is also known as hyaloplasm .
The watery component can be more or less gel-like or liquid depending on the milieu's conditions and the activity phases of the cell. In the first case, it is named cytogel and is a viscid solid mass. In the second case, called cytosol, is a liquid in movement. In general, margin regions of the cell are gel-like and the cell's interior is liquid.
The insoluble constituents of the cytoplasm are organelles (such as the mitochondria, the chloroplast, lysosomes, peroxysomes, ribosomes), several vacuoles, cytoskeletons as well as complex membrane structures (e.g. endoplasmic reticulums or the golgi apparatus).
While all cells possess a cytoplasm, cells from different biological domains can differ widely in the characteristics of their cytoplasms. In the animal kingdom, cytoplasm occupies nearly half the cell's volume while in vegetal cells, the cytoplasm occupies much less space because of the presences of vacuoles.
The cytoplasm plays a mechanical role, i.e. to maintain the shape, the consistency of the cell and to provide suspension to the organelles. It is also a storage place for chemical substances indispensable to life. Vital metabolic reactions take place here, for example anaerobic glycolysis and proteic synthesis.