The substance of the * protoplast of cells. It is composed of about 90% water in highly active cells although the figure may be as low as 10% in dormant cells. Proteins and amino acids account for approximately 65% of the dry weight, lipid material about 16%, and simple sugars about 12%. There are also small quantities of a wide variety of other organic compounds and mineral salts. Physically protoplasm is a colloidal system of at least three phases; an aqueous solution of organic and inorganic compounds, a disperse phase consisting of oil droplets forming an emulsion, and a framework of protein molecules forming fine fibrils and tubules. Proteins are capable of changing form and so altering viscosity. In addition protein and phosphoglyceride molecules are organized into * cell membranes , which are the basis of the structure of all * organelles. The substance of the nucleus is termed nucleoplasm, while the remainder of the protoplasm is called * cytoplasm. |
