Protoplasm

Protoplasm

Protoplasm (Greek, proto=first; plasma=organization) is the basic living substance of the cell. J.E.Purkinje and Hugo von Mohl proposed the name protoplasm in 1839. It is associated with different metabolic processes of the cell.

Physical properties

It is translucent jelly like substance. In physical form it may be granular, alveolar, fibrillar or reticular. Protoplasm may exist in sol or in a gel state. Sol can stream easily and gel is more viscid. Sol can change to gel condition under certain conditions and gel can transform into sol. In sol state the minute particles present in protoplasm can move freely and strike each other and move independently. This is called Brownian movement after its discoverer Robert Brown (1827). In gel condition these movements are not found

According to modern scientists protoplasm is a colloidal substance with water as the continuous phase and fatty substances, carbohydrates, crystals, ions forming the dispersed phase. Thus colloid is a mixture in which large or small but invisible particles (0.0001-0.000001 mm) are suspended in a liquid medium.

If the particles are evenly distributed in a liquid medium and the mixture can flow easily it is called sol state. Thus the Brownian movement and continuous suspension medium (liquid medium) are characteristics of sol state. If the particles are arranged in a net work and the mixture does not flow the colloid is called to be in gel state.

If the soluble substance is solid in nature it is called colloidal suspension and if the soluble substance is liquid it is called colloidal emulsion.

Chemical properties

Protoplasm contains different elements. Carbon, hydrogen, oxygen and nitrogen form 95% of protoplasm and the rest is formed by phosphorus, chlorine, potassium, sulphur, sodium, fluorine, calcium, magnesium and iron. Apart from these zinc, silicon, manganese, iodine, nickel etc. are present as a trace elements. These are not present as free state but are present in the form of organic or inorganic compounds. About 60-70% of protoplasm is inorganic part including water, dissolved gases and inorganic salts. The rest 30-40% is formed by organic part including proteins, fats, carbohydrates, enzymes and nucleic acids.

% of different chemical elements present in protoplasm.

Oxygen 63.00%

Carbon 20.00%

Hydrogen 10.00%

Nitrogen 02.50%

Calcium 02.50%

Phosphorus 01.14%

Potassium 00.11%

Sulphur 00.14%

Chlorine 00.10%

Fluorine 00.10%

Sodium 00.10%

Magnesium 00.07%

Iron 00.01%

Zinc trace

Silicon trace

Manganese trace

Iodine trace

Nickel trace

% of different compounds present in protoplasm

Inorganic

Water 80.00%

Inorganic salts 01.00%

Organic

Proteins 12.00%

Fats 30.00%

Carbohydrates 01.00%

Nucleic acids 02.00%

Steroids 00.50%

Other substances 00.50%

Inorganic compound

(i) Water. It is the main constitute of protoplasm and varies between 60-90% in different animals

(ii) Gas. Protoplasm uses O₂ and gives out CO_2.

(iii) Inorganic salts. Chlorine, phosphate, carbonate and sulphate of Na, K, Ca, Mg and Fe are present. For coagulation of blood Ca is needed. Mg, Ca and phosphorous are used for building bones. Fe is needed to form haemoglobin. Chloride is found in blood tissue-fluid.

Organic compound

(i) Protein (about 12-14% of protoplasm). C, H, O and N are present in protein. Sulphur, phosphorus, magnesium, iron and iodine are also present in it. These form amino-acids which combine to form protein. Protein molecules are larger than fat and carbohydrate molecules. Protein can be converted into carbohydrate. Carbohydrates into fat and fat into carbohydrate in the body. Every species has special type of protein

(ii) Carbohydrate. This contains C, H and O. sugar and starch are well known carbohydrates. Energy is obtained from sugar. Due to the oxidation of sugar CO₂ and energy are liberated. Energy is used by the animal and CO₂ is expelled out.

C₆H₁₂O₆ (sugar)+6CO₂=6H₂O+6CO₂+energy

Carbohydrates cannot be converted into proteins in the body

(iii) Fat. It is also formed by C, H, and O. from fatty acids and glycerol also energy is obtained. Fats are insoluble in water but soluble in benzene ether and petrol. It cannot be converted into protein in the body. In cell fat is stored as a small droplets which are used during need. In fat less oxygen is present in proportion to carbon and hydrogen of carbohydrate and fat.

(iv) Enzyme. Different kinds of enzymes are found in protoplasm which act as catalysts to accelerate or diminish the rate of chemical processes within the cell. They are unaltered after the reaction.

(v) Nucleic acids. Deoxyribose nucleic acid (DNA) is found in nucleus and ribonucleic acids (RNA) in cytoplasm. These are formed by sugar, phosphorous and nitrogenous purine and pyramidine bases.

Thus it is found that the elements are present in the form of compounds. The inorganic compounds are mainly water and salts. The organic compounds are mainly protein fat, carbohydrate, nucleic acids etc.z