History:
Dujardin (1835) – discovered the protoplasm and named as “sarcode”.
J.E. Purkinje (1839) – first introduced the term ‘Protoplasm’.
J.S. Huxley (1868) – defined protoplasm as ‘the physical basis of life’.
O. Hertwig (1892) – proposed “Protoplasmic Theory” which states that all living matter, of which animals and plants are formed, is protoplasm.
Protoplasm (Gr. Protos = first, plasma = form) is the general term used for the living substance of cells which is enclosed by the plasma membrane. It may be defined as the complex polyphasic crystallo-colloidal complex that possesses all the properties of life and is found inside the living cells. However, not everything found in the protoplasm is alive, for it contains many living materials. In eukaryotic cells, protoplasm is differentiated into nucleoplasm (inside nucleus) and cytoplasm. Deutoplasm is non-living substances formed by protoplasm during metabolism.
Physical Nature and Properties:
1. Protoplasm is a jelly-like, viscous, translucent, elastic, odorless fluid material. It is 2-10 times more viscous than water.
2. It is a polyphonic colloidal system which may appear differently in different states (phases).
3. Protoplasm can change from a viscous gel state to a more fluid sol state and vice-versa.
4. Protoplasm can undergo growth and division.
5. It has elasticity i.e. it can be stretched as well as compressed.
6. It has irritability i.e. sensitive to different stimuli.
7. Under normal conditions, protoplasm exhibits various movements such as Brownian movement, amoeboid movement, ciliary movement and cyclosis or cytoplasmic streaming.
8. Protoplasm can swell by imbibing water and can shrink by loosing water.
9. It contains non-polar and charged particles. Electrical conductivity is low.
10. It has coagulability. Protoplasm coagulets on heating, electrification contact with harmful chemicals etc. This causes the death of the protoplasm, so that all of its physical and biological properties are lost.
Chemical Nature:
Chemically, the protoplasm is an aquatic fluid mixture, in which water alone constitute 70% to 90% part as solvent. Of the solutes, about 99% are organic compounds and the remaining 1% solutes are inorganic materials found in form of ions or combined with other compounds. The collection of all the bio-molecule of a cell collectively forms cellular pool. Bio-molecules are generally of two types i.e. micro-molecules and macromolecules.
Micro-molecules are low molecular weight organic compounds less than one thousand dalton, e.g., sugars, amino acids, nucleotides, vitamins etc. Macromolecules or biopolymers are high molecular weight (about 1000 Dalton or above) organic compounds, e.g., proteins, polysaccharides and nucelic acids.