It is the essential living substance of cells, indispensable for life. Life depends fundamentally on protoplasm
All living cells contain it, and it serves as the physical foundation for life while carrying out essential duties so J. Huxley called it the “Physical Basis of Life“.
Initially referred to as ‘Sarcode’ by Dujardin, it was later renamed ‘Protoplasm’ by Purkinje. The significance of protoplasm was elucidated by Hugo Von Mohl in 1844, while Max Schultze proposed the protoplasmic theory in 1861, asserting that all living cells consist of protoplasm wherein crucial activities take place.
Physical properties
It possesses several physical properties. It is a complex, granular, elastic, viscous, and colorless substance. Fischer (1894) and Hardy (1899) demonstrated its colloidal nature, categorizing it as a polyphasic/multiphasic colloidal system.
Nature of Protoplasm
There are many views about the nature, some of which are as follows-
Alveolar Theory
The alveolar theory is a now-discarded theory of the structure of protoplasm. It was proposed by the Swiss biologist Karl von Nägeli in 1858.
The alveolar theory states that protoplasm is composed of a continuous phase of liquid, called mioplasm, and a discontinuous phase of droplets, called uritomes. The uritomes are thought to be composed of protein and other substances.
The alveolar theory was based on the observation that protoplasm often appears to be granular under a microscope. Nägeli believed that the granules were actually uritomes. He also believed that the uritomes were responsible for the various functions of protoplasm, such as metabolism, growth, and reproduction.
Granular Theory
The granular theory is a theory of the structure of protoplasm that was proposed by Richard Altmann in 1893.
The granular theory states that protoplasm is composed of a homogeneous fluid medium, called bioplasm, in which are suspended numerous minute granules, called bioblasts. The bioblasts are thought to be the basic units of life, and they are responsible for the various functions of proto-plasm, such as metabolism, growth, and reproduction.
The granular theory was based on the observation that protoplasm often appears to be granular under a microscope. Altmann believed that the granules were actually bioblasts. He also believed that the bioblasts were responsible for the various functions of protoplasm.
Reticular Theory
The reticular theory is a now-discredited theory that states that protoplasm is composed of a continuous network of fibrils. The theory was proposed by Joseph von Gerlach in 1871, and it was based on the observation that protoplasm often appears to be granular under a microscope. Gerlach believed that the granules were actually interconnected fibrils.
The reticular theory was supported by the work of Camillo Golgi, who developed a staining technique that allowed him to see the fibrils in protoplasm. However, Golgi’s staining technique also allowed him to see the individual cells, and he eventually came to believe that protoplasm was composed of individual cells.
Fibrillar Theory
The fibrillar theory of protoplasm is a now-discredited theory that states that protoplasm is composed of a network of fine fibrils. The theory was proposed by Hanstein, Klein, and Carnoy in the late 19th century, and it was based on the observation that protoplasm often appears to be granular under a microscope. These scientists believed that the granules were actually interconnected fibrils.
Colloidal Theory
The colloidal theory of protoplasm is a theory that states that protoplasm is a colloidal system. A colloidal system is a mixture of two phases: a dispersed phase and a continuous phase.
The dispersed phase is made up of small particles that are dispersed throughout the continuous phase. The continuous phase is usually water, but it can also be other liquids or gases.
In the colloidal theory, the dispersed phase is thought to be composed of proteins, nucleic acids, and other macromolecules. The continuous phase is thought to be composed of water and other small molecules.
The colloidal particles are thought to be responsible for the dynamic properties of protoplasm, such as its ability to flow and change shape. The continuous phase is thought to be responsible for the structural properties of protoplasm, such as its ability to maintain its shape.
The colloidal theory was first proposed by Richard Altmann in 1893. It has been supported by a number of studies that have shown that protoplasm has the properties of a colloidal system. For example, protoplasm is able to form gels and sols, which are two types of colloidal systems. Gels are solid-like systems, while sols are liquid-like systems. Protoplasm can also be dispersed in water, which is a characteristic of colloidal systems.
Here are some of the evidence that supports the colloidal theory:
- It is able to form gels and sols, which are two types of colloidal systems.
- It is able to be dispersed in water, which is a characteristic of colloidal systems.
- The components of it, such as proteins and nucleic acids, have the properties of colloidal particles.
Chemical properties
Regarding its chemical composition, water constitutes the primary component (95%). However, due to continuous changes and its lack of constancy, determining its exact chemical composition remains challenging.
It contains the following-
Water (75-85%), Protein (7-9%), Carbohydrates (2-2.5%), Lipids (1-1.5%), Inorganic substances (1-1.5%), RNA (0.7%) and DNA (0.4%).
Functions
Here are some of the functions of protoplasm:
- Metabolism: It is responsible for the chemical reactions that take place in the cell. These reactions allow the cell to obtain energy, build new molecules, and break down waste products.
- Growth: It is responsible for the growth of the cell. As the cell grows, It increases in size and complexity.
- Reproduction: It is responsible for the reproduction of the cell. When a cell divides, it is divided into two new cells.
- Movement: It is responsible for the movement of the cell. It can flow around the cell, allowing the cell to move from one place to another.
Read in Hindi – जीवद्रव्य सामान्य परिचय एवं प्रकृति
