Different cells have different shapes. They can be round, oval, oblong, round, oblong, flat, pointed, macule shaped, polygonal, irregular etc. Branched filaments are seen in some cells.

The word Cytology is formed from two Greek words kytos meaning cell and logos meaning discussion. Cytology means discussion of cells. The branch of biology that deals with the size, shape, type, physical and chemical structure, division, growth, development and biological functions of cells is called Cytology. The father of cytology is Robert Hooke (1635-1703). But the father of modern cytology is Carl P. Swanson (1911-1996).

1. Cell is the structural and functional unit of living organism.
2. It is the basic unit of life.
3. It is covered by a semipermeable membrane.
4. New cells are formed from old cells.
5. It can grow in a controlled manner. After obtaining certain shape divides and increases in number.
6. It maintains the homeostatic state of the body.
7. Cells contain all the structural and molecular components for life. It contains cytoplasm.
8. It has adaptability. It can be adapted and transformed as needed.
9. Essential substances can move through it.
10. It can respond to any stimulus. It has the ability to respond to changes in the environment.
11. Cells have their own energy production systems. The energy produced is stored as ATP.
12. Cells contain nitrogen-containing polymeric material that enables replication.
13. All cells are self-reproducing.
14. Inherited cells contain signals for hereditary characteristics. It passes from one cell to another.
15. It causes body metabolism.
16. Every cell has a definite life span and cell death occurs after a certain period of time.
17. Cells obtain energy by absorbing essential raw materials from the environment and synthesize organic molecules.
18. It is able to maintain internal balance.
19. It contains all the genetic information and transmits it from generation to generation.

In 1658, Jessner observed the structure of proteases and gave the first idea about cells. He named it Foraminifera. In 1665, Robert Hooke, an engineer of the British Royal Society of London, observed that a wooden ship was stationary but floated in water. A thin section of the shell was observed under a self-made microscope with 30x magnification and he saw numerous tiny honeycomb-like cells or cells. He saw that these kuthuris were like small cells or ivashas for the accommodation of monks or priests of ashrams and inmates of jails. So he named these tiny cells cells. He published all the observed information in the book called Micrographia. The discovery of the cell marked the beginning of cytology. Today it is known as cell biology or molecular biology.

In 1674 Dutch scientist Antonie Van Leeuwenhoek first observed protozoa, bacteria, red blood cells, sperm etc. Important information about the cell was provided by – Grew (1682), Wolff (1759), De Mirbel (1802), Ocken (1805), Lamarck (1809) and Drochet (1824).

In 1825, French scientist Francis Rashpal said that all cells are created from pre-existing cells. In 2019, American scientist William Kalin and his colleagues discovered a mechanism for sensing and adapting cells to oxygen abundance. In 1931, German scientists Max Knol and Ernst Ruska noted the microscopic structure of cells and organelles. Scientists believe that cells appeared 3.5 billion years ago.

In 1920, Alixander Operin and J.B.S Harold said, organic molecules or amino acids were formed by the friction of methane (CH4), ammonia (NH3), hydrogen (H2) and water (H2O) in the atmosphere.

In 1953, Stanley Miller and Harold Urey produced amino acids in the laboratory by passing an electric current through a mixture of methane, ammonia, hydrogen and water.

Many people think that the first life is RNA. Proteins are then made from RNA. This idea is known as the RNA-World hypothesis.

1. Amino acids were formed by the friction of atmospheric methane (CH4), ammonia (NH3), hydrogen (H2) and water (H2O) due to lightening.
2. Carbon compounds and polymers were formed from amino acids in the deep sea.
3. A phospholipid bilayer was then formed with the polymer.
4. RNA was created from polymers.
5. Proteins were created from RNA (RNA-World).
6. Early cells were created from proteins.
7. The nucleus of the primitive cell is well formed and enveloped by the cell membrane to become a true cell.
8. Aerobic bacteria entered true cells, transformed into mitochondria, and evolved into animal cells.
9. Photosynthetic bacteria entered animal cells, transformed into chloroplasts, and evolved into plant cells.

Primordial cells are created from the original source. The original cell’s DNA becomes the nucleus and forms the true cell. Aerobic bacteria enter true cells and transform into mitochondria and form animal cells. Photosynthetic bacteria enter animal cells and transform into chloroplasts and form plant cells. Endosymbiosis is the process by which bacteria enter and survive in nucleated cells.

1. According to Jean Brachet (1961), the cell is the basic structural unit of an organism.
2. According to Loewy & Siekevitz (1963), a cell is a unit of biological function which is surrounded by a permeable membrane and is self-reproducing.
3. According to C. P. Hickman (1970), the cell is the unit of biological structure and function and is the smallest biological unit capable of self-regulation and reproduction.
4. According to Swanson and Webster (1978), the cell is the basic unit of physical existence of life.
5. According to De Roberties (1979), the cell is the basic structural and functional unit of an organism.
6. According to the Merriam Webster dictionary, a cell is a microscopic lump of protoplasm covered by a semipermeable membrane, containing one or more nuclei and other cell organelles and their components, capable of performing the basic functions of life either singly or by interaction with other cells, and is the smallest independent functioning structure of life. constitutes a unit.

The word Cell is formed with the Latin word Cellula meaning little box. Cell means small cell. The structural and functional unit of an organism is called a cell. In order to keep the body’s movement normal, various biochemical processes are carried out in the cells – photosynthesis, growth, protein synthesis, DNA and RNA synthesis, hormone and enzyme synthesis etc. Hence cell is called the functional unit of living organism. It is called the life-forming unit.

1. Decomposable organic compounds, heavy metals, cyanide, sulphur, lead, mercury, copper, zinc, chromium, cadmium, phenol, arsenic, nickel, ammonia, chlorine compounds, phosphates, nitrates etc. are emitted from industrial plants. All these decaying substances cause bad smell. Contaminates soil, water and air. Sometimes it causes acid rain. These substances are converted into pollution free substances with the help of microorganisms through biotechnology.
2. Insoluble chemicals such as H2S, SO2, NO2, DDT, carbon tetrachloride etc. are emitted from industrial plants. All these non-degradable substances are neutralized by biological technology.
3. Chlorine is used to bleach raw materials in the paper industry. Paper and pulp industries emit lignin, cellulose and chlorine. Decomposition of lignin and chlorine with the help of enzymes.
4. A yeast called Torula grows in wastes from paper and paper pulp. Such waste contains a large amount of protein. Amino acids are made from these wastes.
5. Single cell proteins are extracted from yeast and some bacteria. This protein keeps the environment free of pollutants.
6. A large amount of cellulose waste is released from jute industry, textile industry, cotton industry and silk industry. Cellulose is converted into simpler substances by Cellulomonas and Alcaligenes bacteria. Organic acids, proteins, amino acids, vitamins, ethanol, acetone, glycerin, gutanol etc. are produced from such waste.
7. Lactic acid is produced from milk factory waste. As a result, the environment is free from pollution.
8. Chlorinated waste water can be dechlorinated using species such as Tremetes versicolor, Pholiota mutabilis, Phlebia subserialis etc.
9. In Germany, Ferriflock is produced from waste from aluminum factories. Contaminated water is treated by Ferriflock.

1. Food and Bioenergy Production.
2. Production of ethanol, lactic acid, acetone, glycerin, citric acid, gluconic acid etc.
3. Used in detergent, leather, textile and dairy industries.
4. Biogas production.
5. Enzyme and hormone production.
6. Insulin and interferon production.

1. Micropropagation and mycorrhiza should be used for soil regeneration.
2. Nitrogen-fixing bacteria should be used with leguminous crops and other plants to restore soil fertility.
3. Plants that grow on degraded land must be created. Stress tolerant plants can grow on degraded land.
4. Microorganisms like Ganoderma lucidum, Thiobacillus ferroxidan etc. should be used to remove toxic substances from the soil.