The living substance in a cell is called:

Protoplasm is the living content of a cell that is surrounded by the plasma membrane.

The living substance in a cell is called protoplasm. It is surrounded by a plasma membrane. It's a general term for a cytoplasm. Protoplasm is composed of many small molecules such as ions, amino acids, proteins, lipids, polysaccharides, nucleic acids, monosaccharides and water.