Colloidal Nature & Properties of Protoplasm
Colloidal Nature of Protoplasm
Protoplasm shows the colloidal nature. It is a complex, semi liquid, semitransparent, Gel like and granular substances. It consists about 75 – 90 % water in it. Colloidal solution is the mid phase of true solution and suspension.
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For Example : If we dissolve the sugar in water, it completely dissolved and makes a true solution. This true solution is transparent and the size of its particles is 0.001 µ .We can’t see its particles even through the microscope. In a true solution both solute and solvent are present in a molecule form which shows only one phase of the solution. Thus it is called as homogeneous solution
If we dissolve little soil in the water, then it distributed into small particles. We can observe its particles through naked eyes. No microscope is required. This is called the suspension of soil in water. The size of its particles are 0.01 µ or more from it.
There are many substances that does not breakdown into its molecules or ions when dissolve in the solvents, in spite of this the groups of molecules are distributed in the solution. This type of solution is known as colloidal solution. The size of the molecules of the colloidal solution is 0.001 – 0.1 µ. Thus the colloidal solution is heterogeneous solution. The size of these types of molecules groups is bigger than size of the molecules of true solution and smaller than the size of molecules of a suspension solution.
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Protoplasm as Colloidal System
Various organic substances such as proteins, lipids etc. dissolve in water forms polyphase colloidal system. Protoplasm is found in the form of homogeneous colloidal solution. The Proteins molecule of the colloidal protoplasm forms various organelles of the cell and also regulates various biological activities in the form of enzymes.
Colloidal Properties of the Protoplasm
1. Sol And Gel State
The colloidal solution of protoplasm is found in two phases – semi solid or solid phase Gel and a liquid phase Sol. The Gel and Sol phases interchange between each other when conditions are changed. But normally protoplasm is occurring in a Sol phase.
When the dispersed particles get uniformly distributed in the dispersion medium and take the form of a homogeneous solution, it is called sol. In contrast, gel is a group of suspended (dispersed) particles in semi-solid state, in which the dispersed particles form a spongy net-like structure and the spaces between the net are filled with liquid (dispersion medium).
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| Sol & Gel State of Protoplasm |
Both the sol and gel states are capable of transforming into each other. The transformation from sol to gel state is called gelation and the transformation from gel to sol state is called solation.
Factors like temperature, electric charge, chemical substances, pH, liquid static pressure etc. affect its transformation from sol to gel and gel to sol.
2. Electric Charge
Equal electric charge is present on colloidal particles. There is a electric charge present on protein molecules of protoplasm. Due to having the same charge, protein particles get repelled from each other and keep moving here and there in the fluid medium of cytoplasm at a high speed. This movement of particles is called Brownian motion. If the particles have different charges, then they will get attracted towards each other and settle down as a deposit.
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3. Brownian Movement
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| Brownian Movement |
Due to uniform charge on the dispersed particles of protoplasm, they always keep moving in an irregular order. This motion is caused by the collision of the molecules of dispersion medium - water with colloidal particles. It was first studied by Robert Brown in 1827, due to which it was named Brownian motion. With increase in temperature, the viscosity of protoplasm decreases and hence their movement increases.
4. Tyndall Phenomenon
protoplasm shows Tyndall Phenomenon means when a beam of light is focused on protoplasm, then it becomes scattered after colliding with its particles.
5. Absorption
In dispersed state, the surface area of colloidal particles is very high. Due to this, it has a high capacity to absorb other molecules and ions. Various biological and metabolic activities taking place in living cells are also possible due to the colloidal nature of protoplasm. The nature of protoplasm is hydrophilic means it absorbs more water in it.
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