Cell - The Basic Unit of Life & its Historical background

Introduction:

• The cell is the basic unit of life.
• All living organisms are composed of cells.
• Anything less than a complete structure of a cell does not ensure independent living.
• Hence, the cell is the fundamental structural and functional unit of all living organisms.

History:

The cells can only be observed with the help of a microscope because of their small size. The development in the field of microscopy made it easy for the scientists to study a cell.

1. Robert Hooke
 

• In 1665, Robert Hooke named and discovered the cells while observing a thin slice of dead bottle cork under a primitive microscope created by him.
• He is known as the ‘Father of cytology’.
• The word cell means the small compartment and was derived from the Latin language.
• Actually what he observed was a dead cell wall.
• This finding was famous after publishing the work in the book, ‘Micrographia’.

2. Antonie van Leeuwenhoek
 

• Antonie van Leeuwenhoek observed the first living cell cells under a microscope.
• He called them “animalcules” which means the little animals.

3. Robert Brown
 

• Robert Brown, a Scottish botanist, discovered the nucleus for the first time in 1831 in orchids.

4. Schleiden and Schwann
 

• The cell theory was first proposed by Schleiden and Schwann.
• Jakob Matthias Schleiden was a German botanist who first proposed the idea that all plants consist of cells in the year 1838.
• Theodor Schwann was a German zoologist who independently asserted that all animals and plants are made up of cells.

5. Rudolf Virchow
 

• R. Virchow redefined the cell theory in 1855 and presented the idea that all cells arise from pre-existing cells.
• His actual aphorism was 'Omnis cellulae a cellula'.

Detailed explanation:
 

• The cell is the basic building block of life.
• The cellular organisms can be categorized into two categories- unicellular and multicellular organisms, on the basis of the number of constituting cells .
• Unicellular organisms are made up of one cell. They are capable of independent existence and performing the essential functions of life.
• Multicellular organisms are made from more than one cell.
• The activities of an organism are governed by the sum total activities of all the cells in its body.
• The cells are also subdivided into two major groups of prokaryotic cells and eukaryotic cells on the basis of internal architecture.
• Eukaryotic cells include the well defined membrane-bound nucleus whereas the prokaryotic cells show the absence of well organized nucleus.
• Most prokaryotes are unicellular in nature.
• Most eukaryotic organisms are multicellular.
• Eukaryotes are complex organisms and have membrane bound structures called organelles for specific functions. For Example- endoplasmic reticulum, Golgi complex, lysosomes, mitochondria, microbodies, and vacuoles.
• In both prokaryotes and eukaryotes, cytoplasm is the region between the plasma membrane and nucleus.
• The cytoplasm is the main arena of cellular activities.

Frequently asked questions (FAQ)
 

Q1. What is a cell?
Ans:

• The cell is the basic unit of life. All the living organisms are composed of cells.
• Anything less than a complete structure of a cell does not ensure independent living.
• Hence, the cell is the fundamental structural and functional unit of all living organisms.
• All cells divide and reproduce from the pre-existing cells.

Q2. What is a prokaryotic cell?
Ans: The prokaryotic cell exhibits the following characteristics-

• They show the absence of the well-organized nucleus.
• They lack membrane-bound organelles.
• For example, bacteria and blue-green algae (cyanobacteria).

Q3. What is a eukaryotic cell?
Ans: The eukaryotic cell exhibits the following characteristics-

• They exhibit the presence of the well-organized nucleus with nuclear envelope, nucleolus, and nuclear pores.
• They show the presence of membrane-bound organelles such as endoplasmic reticulum, mitochondria, chloroplasts, and golgi apparatus.
• For example, cells of plants, animals, fungi and protists.

Q4. Name the book in which Robert Hooke published his work.
Ans:

• Robert Hooke published his work in the book Micrographia (1665).
• This book recorded some physiological descriptions of minute bodies made by magnifying glasses with observations and enquiries there upon.
• He also used the word “cells” depicting the microscopic honeycomb cavities in cork.

Q5. Name the scientist who first studied living cells?
Ans:

• A.V. Leeuwenhoek (1674) was the first scientist to study living cells.
• He discovered free-living algae (Spirogyra) cells in water in the pond.
• He also observed living cells and termed them as animalcules which are now known as “Bacteria”.

Q.6 Who is known as the father of cytology?
Ans:

• The father of Cytology is Robert Hooke.
• Cytology is referred to as the study of cell structure.