Protoplasm

Protoplasm has been defined as the ‘material basis of life’. The term deutoplasm is used to describe the substances formed by the protoplasm. Protoplasm is divided into nucleoplasm or protoplasm of the nucleus and cytoplasm or extra-nuclear protoplasm. Protoplasm is made of oxygen, carbon, hydrogen and nitrogen, which make up 95% by weight of the body. It also has a group of minerals.

Colloidal nature of protoplasm

Protoplasm has several properties of colloids.

(1) Colloidal particles are in a constant state of motion. The movement, which can be seen under the microscope, is called Brownian movement, after its discoverer Robert Brown.

(2) Colloidal particles have the property of scattering light. When a beam of light passed through colloidal solution it becomes visible. A colloidal solution of proteins in water shows a typical Tyndall cone.

(3) Sol and gel states. Colloidal systems have the property of under going changes in consistency or rigidity. A colloidal suspension can be watery at one time and jelly-like at another.





(4) Electrical Charge. Protein molecules repulse each other because their overall charge is similar. All molecules are either positively charged or negatively charged. However, if the molecules approach one another close enough so that valency forces can act, then they be attracted to each other.

(5) Proteins do not pass through natural membranes, while crystalloids can do so. Thus, proteins can be separated from crystalloids by dialysis. If both substances are placed in cellophane membrane tubing immersed in distilled water, the crystalloids will pass from the tubing into water, but proteins will be retained.

(6) Dry proteins absorb water, and thus undergo hydration. The phenomenon of imbibitions depends upon this property.

(7) Viscosity. The viscosity of the ground substance of the cell varies greatly. It may be as low as that of water, or may be very high in the gelatin cytoplasm of pseudopodia of Amoeba.