Cell: Structure & functions, cell theory.
Every living creature has one thing in common in them i.e. all are made up of cells.
Cells are the basic building blocks of every living being.
A cell can be defined as the fundamental structural and functional unit of life.
Every organ of our body whether it is heart, brain or even bone is made up of millions of cells.
Every cell in the body has its own lifetime, old cells are replaced by new cells.
for example red blood cells have a lifespan of about 120 days.
Cell theory by Schleiden & Schwann.
Cell theory was given by Matthias Schleiden who was a German botanist and Theodor Schwann, a German zoologist.
Schleiden said that every plant is made up of large number of cells, and each cell performs various life processes.
Theodor Schwann announced that all animals and plants are composed of cells, which are the units of structure and function.
These points put together is called as cell theory. It was proposed by Schleiden and Schwann in the year 1839.
Later, Rudolf Virchow added few points to the cell theory
Let’s see what points Rudolf Virchow has added to the theory.
In the year 1858, Rudolf Virchow made an amendment to the cell theory,
He said that all cells arise from preliminary cells.
Let see what are the postulates of the final cell theory
1. The cell is the structural unit of all living beings.
2. The cell is the functional unit of all living beings.
3. All cells arise from preliminary cells.
Meaning of cell theory.
Any part of an animal or a plant, when examined under a microscope, will show a cellular structure,
That means the cell is the structural unit of life.
Any function that occurs in the body is due to the activity in the cell, thus it is the functional unit as well.
Body of an animal or a plant is composed of millions of cells, with a limited lifespan, cells die and are replaced continuously.
New cells are formed by the division of younger cells, this means that new cells are formed from pre-existing cells.
Every life starts with a single cell, for example, the egg inside the ovary of a mother frog is a single cell.
Cell theory was given by Schleiden & Schwann in the year 1839.
Rudolf Virchow made an amendment in the cell theory by adding a point that all cells arise from pre-existing cells.
1. The cell theory has the following postulates. 2. A cell is a structural unit of life 3. A cell is a functional unit of life
3. All cells are formed from preliminary cells.