Explain why the ultimate chemical nature of protoplasm cannot be determined.
Protoplasm is a complex material comprised of two categories of substances. It is because of the complexity of physical properties and chemical properties that the ultimate chemical nature of protoplasm can not be determined.
The first substance is that which is enclosed within the cell membrane. The second substance is the cell membrane itself. Protoplasm is called the "living substance" of the cell. The differentiation of the two categories are cytoplasm and the nucleus; these comprise the protoplasm.
Protoplasm's physical properties vary and range from near-liquid gelatinousness to near-solid gelatinousness. At one end of the range it is near-liquid resembling the white of an egg, while at the other end of the range, it is near-solid resembling jelly. The former near-liquid state is called sol, while the latter near-solid state is called gel.
Chemical properties of protoplasm are divided between inorganic substances and organic substances (organic as in living organisms). The components of the inorganic properties of protoplasm are: water, 90% of protoplasm; mineral salts; gasses (e.g., oxygen and carbon dioxide). The components of the organic properties of protoplasm include enzymes, lipids, carbohydrates, nucleic acids, and proteins.
[For more information, see "Protoplasm," Biology Department, The University of the Western Cape, South Africa.