NEET EXAM BIOLOGY NOTES-PROTOPLASM
Fluid along with all the structures of cell bounded within the limits of cell membrance, is known as protoplasm. So protoplasm includes plasma membrane, cytoplasm and Nucleus. Protoplasm of a single cell is called Protoplast (wall less cell).
Origin of the word protoplasm has taken from a greek work
(Protos = first, Plasma = organisation).
Protoplasm was first observed by Corti, 1772.
Felix Dujardin, 1835 observed jelly like substance in animal cells (protozoa) and gave the name ‘Sarcode’.
J.E. Purkinje, 1840 observed similar substance in plant cells and coined the term ‘Protoplasm’.
Hugo Van Mohl, 1846 studied the nature of protoplasm present in the embryonic cell of plants and explained the importance of protoplasm in the cell division.
Max schultze, 1861 established similarity between sarcode and protoplasm. Schultz proposed protoplasm theory (name given by O. Hertwig). Max schultze firstly told that protoplasm is physical basis of life.
- J.S. Huxley, 1868 wrote a book ‘‘Protoplasm is physical basis of life’’
- Rinke and Roderwald, 1881 first of all performed the chemical analysis of protoplasm.
PHYSICAL NATURE OF PROTOPLASM :
Several theories are proposed to explain physical nature of protoplasm.
(1) Alveolar theory – Butschli (1892). Protoplasm is a foamy emulsion consists of bubbles of high density fluid.
(2) Granular theory – Altman (1893). Fine granules are homogenously distributed into the homogenous medium of Protoplasm. Granules were termed as Bioplast or Cytoplast
(3) Fibrillar theory – Flemming, (1894). Microscopic filaments (Micelles or mitomes) like structures are dispersed in a liquid matrix (Paramitome or Hyaloplasm).
(4) Reticular theory – Hanstein, Klein and Carnoy,(1898) Protoplasm is a mesh work of microscopic filaments.
(5) Colloidal theory – Fisher 1894, Hardy 1899 and Wilson1925.
This is most acceptable theory for protoplasm. According to this theory, the protoplasm is a Polyphasic Colloidal System.
PHYSICAL Properties OF PROTOPLASM :
(1) Protoplasm is a translucent, odourless and polyphasic fluid.
(2) Protoplasm is a crystallo-colloid type of solution.
Protoplasm is a mixture of such chemical substances among which some form crystalloid i.e. true solution (Sugars, Salts, Acids, Bases etc.) and others which form colloidal solution (Proteins, lipids etc.)
(3) Size of colloidal particles (0.001 to 0.1 mm) is between true solution and suspension.
(4) Colloidal systems composed of two stages. (i) Dispersion phase or continuous form or intermicelleus and (ii) Dispersed phase or discontinuous phase or Micellus
TYPE OF COLLOIDS :neet exam biology notes
On the basis of dispersion and dispersed phases there are four types of colloids –
(i) Sol = Dispersion phase is liquid and dispersed phase is solid. In sol stage, protoplasm is less viscous. Protoplasm in sol stage occurs in majority of living cells.
(ii) Gel = Dispersion phase is solid and dispersed phase is liquid. Protoplasm is more viscous e.g. Skin Cells.
(iii) Emulsion – Both stages are liquid i.e. fluid colloidal particles are dispersed in a liquid matrix e.g. blood plasma composed of both sol and emulsion.
(iv) Aerosol – solid particles remain suspended in gas e.g. smoke. Aerosol does not occur in living system.