A living system is made up of organs, organs of tissues, and tissues of cells. A cell contains protoplasm. Protoplasm is the name of living matter. All the biological properties of living beings like growth, metabolism, irritability, reproduction, etc. are basically the properties of protoplasm. Therefore, protoplasm has been called the physical basis of life by Huxley (1868).
Physico-Chemical Concept of Life. Before the beginning of modern era in physical sciences, life was considered to be something mysterious which was governed by its own special laws of vital forces, that could not be resolved into simpler physical and chemical principles. This is called vitalistie concept of life. However, in the nineteenth century the substances constituting the living matter were studied. It was found that all organic matter had its origin in the inorganic matter and life processes were governed not by vital forces but by discrete and simple physical and chemical principles. It is known as physic-chemical (or mechanistic) concept of life. It considers that life is simply an external manifestation of a large number of physical and chemical reactions. Further, the life in its vast diversity and complexity is derived by blending and interactions of a limited number of elements.
There is no well studied process of life which cannot be explained in terms of physical and chemical principles. Thus absorption, translocation and utilization of water and minerals salts, movements, phenomena of respiration and photosynthesis, formation of different types of organic substances, cell division, growth and differentiation of cells tissues or organs, transfer of hereditary characters, control of metabolic activities, development of variations, adaptations, adaptations, etc can all be explained on the basis of physical and chemical reactions.
Chemically a living system is made up of both inorganic and organic compounds.
Inorganic compounds
They are represented by water, salts and gases.
Gases. They include oxygen, carbon dioxide and some inert gases (e.g. nitrogen) Oxygen is obtained from the atmosphere. It is utilized in respiration. Carbon dioxide is evolved in respiration. It is a waste product and is expelled from the body.
Water. It contained 60-95% of a living system and 80-95% of the protoplasm. A molecule of water has two atoms of hydrogen connected to an atom of oxygen by covalent bonds.
Oxygen atom attracts electrons to a great extent than do hydrogen atoms. Therefore, oxygen end of water molecules has a slight negative charge while hydrogen ends show a slight positive charge. The two different charges help water molecules to form three-dimensional aggregates. The bonds formed among the water molecules are called hydrogen bond. Because of the presence of hydrogen bonds amongst water molecules, water a high specific heat, cohesion force and ability to stick to walls or adhesion force. The two different types of charges also allow water molecules to form shells around ions and charged ends of non-electrolytes. In this way water helps to disperse ions and molecules. Water molecules can also dissociate to form ions, H? (or H3O?) and OH’.
Physico-Chemical Concept of Life. Before the beginning of modern era in physical sciences, life was considered to be something mysterious which was governed by its own special laws of vital forces, that could not be resolved into simpler physical and chemical principles. This is called vitalistie concept of life. However, in the nineteenth century the substances constituting the living matter were studied. It was found that all organic matter had its origin in the inorganic matter and life processes were governed not by vital forces but by discrete and simple physical and chemical principles. It is known as physic-chemical (or mechanistic) concept of life. It considers that life is simply an external manifestation of a large number of physical and chemical reactions. Further, the life in its vast diversity and complexity is derived by blending and interactions of a limited number of elements.
There is no well studied process of life which cannot be explained in terms of physical and chemical principles. Thus absorption, translocation and utilization of water and minerals salts, movements, phenomena of respiration and photosynthesis, formation of different types of organic substances, cell division, growth and differentiation of cells tissues or organs, transfer of hereditary characters, control of metabolic activities, development of variations, adaptations, adaptations, etc can all be explained on the basis of physical and chemical reactions.
Chemically a living system is made up of both inorganic and organic compounds.
Inorganic compounds
They are represented by water, salts and gases.
Gases. They include oxygen, carbon dioxide and some inert gases (e.g. nitrogen) Oxygen is obtained from the atmosphere. It is utilized in respiration. Carbon dioxide is evolved in respiration. It is a waste product and is expelled from the body.
Water. It contained 60-95% of a living system and 80-95% of the protoplasm. A molecule of water has two atoms of hydrogen connected to an atom of oxygen by covalent bonds.
Oxygen atom attracts electrons to a great extent than do hydrogen atoms. Therefore, oxygen end of water molecules has a slight negative charge while hydrogen ends show a slight positive charge. The two different charges help water molecules to form three-dimensional aggregates. The bonds formed among the water molecules are called hydrogen bond. Because of the presence of hydrogen bonds amongst water molecules, water a high specific heat, cohesion force and ability to stick to walls or adhesion force. The two different types of charges also allow water molecules to form shells around ions and charged ends of non-electrolytes. In this way water helps to disperse ions and molecules. Water molecules can also dissociate to form ions, H? (or H3O?) and OH’.
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