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Introduction of Cell Biology

Introduction of cell biology:
Cell biology is a branch of biology which deals with study of various functions of organisms at its cellular level

Cell is a smallest unit of organism and is the structural and functional unit of life. Cytology is a branch of cell biology which deals with the study of the structure, constitution and the functions of cells.


Cell unit:
Depending on the number of cells present in the organism, they are classified as Unicellular organism and Multicellular organism.

Unicellular organism:

  • Made up of only one cell, example – Bacteria, yeast, Amoeba
  • Observed under microscope, Exception – Egg cells
  • Two types of cell– Prokaryotic (No nucleus) and Eukaryotic (Well organized cell nucleus)

Multicellular organism:
  • Made up of many cells, example – Animals, Human, Plants
  • Three types of cells – Undifferentiated, Differentiated and Dedifferentiated
  • Undifferentiated cells – cell division is possible, example – Human stem cell and Plants meristems
  • Differentiated cells – Transformed for specific function, example – RBC in blood and Sclerenchyma in plants
  • Dedifferentiated cells – Transformed for differentiated cells to undifferentiated state and useful in healing of wound and for secondary growth in plants.

Life of Multicellular organism:



All the cells of Multicellular organism are having same genetic material buy all genes are not expressed in all cells. Hence any cell of the body is capable of producing entire body. These characters are called totipotency.

In short, all metabolic activities carried out by organism is performed by cell and all physiological functions are performed at cellular level. Hence, cell is considered as a basic unit of life.


Discovery of cell:
Robert Hooke is the first scientist who discovered the cell. He observed a many compartment in the section of bark of Oak tree, under the microscope and named it as cells.

Later, Anton Leeuwenhoelck has described bacteria and protozoan under microscope. Robert Brown discovered the nucleus and Mohl and Purkinje has explained the protoplasm.


Cell Theory:
Schleiden has explained that plant tissues are made up of cell and then Schwann has observed that animal bodies are made up of cells and cellular products. Later both Schleiden and Schwann have jointly proposed cell theory, which includes
  • All organisms are made up of cells and their products.
  • Cell is the structural and functional unit of organisms.

Later, Virchow discovered that all new cells arise through cells division of preexisting cells and was added into cell theory.

Self study:
Example-1: Match the following:

(A) (B)
Robert Hooke Discovery of bacteria and protozoan cell
Robert Brown Discovery of cell nucleus
Leeuwenhoelek Discovery of protoplasm
Mohl and Purkinje Discovery of cell

Answer:
(A) (B)
Robert Hooke Discovery of cell
Robert Brown Discovery of cell nucleus
Leeuwenhoelek Discovery of bacteria and protozoan cell
Mohl and Purkinje Discovery of protoplasm

Example-2:  Define - totipotency
a)  Single cell is capable of producing entire body
b)  Study of physiological functions performed at cellular level
c)  Metabolic activities performed by cell
d)  None of above

Answer: Totipotency – single cell is capable of producing entire body.

Example-3: Which of following statement is not included in cell theory?
a)  All organisms are made up of cells and cellular products
b)  Cell is a structural and functional unit of organisms
c)  New cells are formed through division of pre-existing cells.
d)  Cells differentiate and constitute tissues, organs and organ system.

Answer: Cell theory doesn’t include the statement - Cells differentiate and constitute tissues, organs and organ system.

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