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Protoplasm: The Composition and

Chemical Nature of Protoplasm

by Saritha Pujari -- Protoplasm

The Composition and Chemical Nature of Protoplasm!

Generally the protoplasm consists of oxygen, carbon, hydrogen and nitrogen.

Approximately the oxygen is 62%, carbon 20%, hydrogen 10% and nitrogen 3%. The

remainder of 5% part contains about thirty elements, of which calcium (Ca), iron (Fe),

magnesium (Mg), chlorine (Cl), phosphorus (P), potassium (K), sulphur (S), etc., are

important ones. In addition to these, boron (B), copper (Cu), fluorine (F), manganese

(Mn) and silicon (Si) are found in small traces. In certain special cells alcohol, cobalt

(Co) and zinc (Zn) are also found.

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All these elements are found in ionic state or essentially found in adenosine

triphosphate (ATP). All chemical reactions going on in the protoplasm obtain energy for

their performance from ATP. The protoplasm contains 67-75% of water. Moreover,

certain gases such as carbon-dioxide and oxygen remain dissolved in it.

The protoplasm of each cell contains several organic substances of which carbohydrates,

fats, proteins, and nucleoproteins are important ones. These organic substances make

protoplasm by molecular combination.

Carbohydrates:

About thirteen percent part of protoplasm consists of carbohydrates. The carbohydrates

contain carbon, hydrogen and oxygen. The important carbohydrates areglucose,

sucrose, starch, cellulose, glycogen, etc. The granules of carbohydrates either remain

suspended or dissolved in the cytoplasm. They are mainly responsible for the

production of energy.

Fats:

The fats or lipids consist of carbon, hydrogen and oxygen elements. They are formed by

the combination of glycerol and fatty acids. They contain lesser amount of oxygen than

carbohydrates. When they are chemically decomposed the energy is being liberated.

They contain much more energy in comparison to carbohydrates. The cell membrane

consists of fat.

Proteins:

About fifteen per cent of the protoplasm consists of proteins. In addition to carbon,

hydrogen and oxygen elements, the proteins essentially contain nitrogen. Usually they

contain sulphur and sometimes phosphorus too. The proteins are formed by the

combination of the molecules of amino-acids.

About twenty amino-acids are found in the nature that give rise to different kinds of

proteins by their molecular combination. A protein molecule is made of hundreds orthousands of amino-acid molecules joined together by peptide links into one or more

chains, which are variously folded. There are 20 different kinds of amino-acids

commonly found in proteins, and most of these usually occur in any one protein

molecule; they are arranged in the chain in a sequence which is exactly the same in all

molecules of a given kind of protein.

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The possible different arrangement of the amino-acids are evidently practically infinite,

and the diversity is fully exploited by living things, every species having kinds of protein

molecule peculiar to itself.

A protein molecule is very large (molecular weight from about 20,000 up to severalmillions), and dissolved proteins form therefore colloidal solutions. Proteins are not

soluble in fat solvents. Many are soluble in water or dilute salt solutions (e.g., globulins);

others, with elongated (fibrous) molecules, are insoluble in these solvents (e.g.,

scleroproteins, myosin).

Proteins are synthesized from amino-acids by all living things; the precise sequence of

the amino- acids being determined by the sequence of nucleotides in nucleic acids. The

proteins are destroyed by proteolytic enzymes. They are frequently combined with other

substances, especially nucleic acids (nucleo-proteins), carbohydrates (glycoproteins),

fats (lipoproteins).

Nucleoproteins:

They are most complex substances ever found. They are compounds of nucleic acid and

protein. The protoplasm contains two types of nucleic acidsribonucleic acid (RNA)

and deoxyribonucleic acid (DNA). The RNA is found in the complete cell, whereas DNA

remains confirmed in the nucleus. Ribonucleic acid (RNA), a molecule consisting of a

large number of nucleotides attached together to form a long strand one nucleotide

thick. Deoxyribonucleic acid (DNA) is mainly found in the genes of chromosomes.

The DNA, a compound consisting of large number of nucleotides attached together in a

single file to form a long strand. Usually two such strands are linked together parallel to

each other by base pairing, and coiled into a helix. In each cell the DNA and RNA are

mainly concerned with the metabolic activities.

Numerous RNA and DNA are formed within the living cells. The nucleic acids of two

different living beings are never identical. The RNA and DNA control all the metabolicactivities going on within the living cells. They play an important role in the origin of

life. DNA is the material of inheritance of almost all living beings.

Other chemical substances:

Besides abovementioned organic substances several other inorganic substances are also

found in the living cells in small quantities. These substances are specially concerned

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with the cell metabolism. Some of these substances are found in all cells whereas some

are confined to certain special cells. Various pigments, latex, alkaloids, vitamins,

hormones, antibiotics and some other substances are found within the plant cells.

Thus, the carbohydrates, fats, proteins, nucleoproteins and several other chemicalsubstances make the protoplasm by their molecular combination. The molecules of all

these substances are well organized and form protoplasm.

In addition to these the molecules of living cells possess special characteristics by which

various chemical reactions take place and with the result the energy liberates. This

energy is utilized in the performance of the metabolic activities of the cells. Thus, this

becomes an established fact that all constituents of the cell form a very powerful

organization by their combination, which is living and quite active.