Cell Theory: Definition, Modern Version of Cell Theory

 Cell Theory: Definition, Modern Version of Cell Theory 

INTRODUCTION:

"All living things are made of cells. The cells are the structural and functional unit of life. New cells arise from pre-existing cells." This statement is what makes the "Cell Theory".

       The above statement at the moment seems to be so obvious, just like "sunrises in the East". However, two centuries from now, when researchers didn't have all automated gadgets handy out in their folds, it might have been an enormous leap in the field of biology. 

Even from the time of the discovery of the cell by Robert Hooke in 1665, it took more than 170 years to develop the cell theory.

  Important QnA of cell theory:

Question: Define Cell theory. Give a modern version of cell theory.

                   Or

 Question: 

What are the three parts of cell theory? Give the modern version of cell theory.

Answer:  

Cell theory is a fundamental scientific theory of biology which states,

1. All organisms are composed of cells.
2. The cell is the basic unit of life.
3.  All cells derive from the pre-existing cell.

These are the 3 parts of cell theory.

The classic theory was proposed considering the work of two scientists who independently worked on plants and animals.

Matthias Schleiden was a German botanist who discovered in 1838, that plants are made up of cells.

Diagram: Structure of plant cell 

Theodor Schwann was a British physiologist, who in the same year, i.e. 1838, discovered that animals are made up of cells.

Diagram: Structure of Animal Cell 

The cell theory was formally articulated in 1839 by Schwann and Schleiden which states that " all organisms are made of cells".

 

 After around two decades in 1858, Rudolf Virchow ( full name: Rudolf Ludwig Karl Virchow) modified the classic cell theory by adding " Omnis cellula - e - cellular" which means, " cells arise from pre-existing cells".

Modern Cell Theory:

The following facts provide the basis of the Modern Cell theory.

1.  All known living organisms are made up of cells.
2. The " cell" is the basic structural and functional unit of all living things.
3. All cells come from pre-existing cells by division. ( Spontaneous generation does not occur).
4. The activity of each independent cell always guides the activity of the organism.
5. Energy flow occurs within all cells ( i.e all metabolic reactions)
6. All cells are the same in their chemical composition. The individual organisms of the same species show similar cellular constitutions.
7.  The DNA in the chromosome of the cell contains the genetic information that is passed from one cell to the other during cell division.

Conclusion:

After the formulation of cell theory, these many years have gone by. All these years have had minor changes made to it and in future if research opens up new tenets to the concept which can be added or can even go the other way around, invalidating the whole theory, as time always has something new to unfold.

Next: Cell Cycle