Q.Define - Tyndall effect.

The protoplasm theory holds that a single living substance, protoplasm, is the 'physical basis of life' inside every cell - a concept built up by Corti (first observation), Dujardin (1835, 'Sarcode' in animal cells), Purkinje (1839, coined 'protoplasm' for plant-cell sap), Von Mohl (1846), Max Schultze (1861, unified Sarcode and Protoplasm), Hertwig (1892, named the theory) and Huxley (1868, called it the 'physical basis of life'). Chemically, protoplasm is a complex colloidal system (Fisher, 1894; Hardy, 1899) - mostly water, carrying true (crystalloid) solutes such as sugars, salts and acids alongside colloidal solutes such as proteins and lipids - and it exists in either a semisolid 'gel' state or a fluid 'sol' state, interconverting by solation and gelation, which underlies Brownian movement, amoeboid movement and cytoplasmic streaming (cyclosis). Protoplasm is translucent, odourless, has a viscosity of 2-20 centipoises, a refractive index of about 1.4, a pH around 6.8, is about 90% water (10% in dormant seeds), and is built mainly (96%) of carbon, hydrogen, oxygen …