Difference between animal cell and Plant Cell

Aug 09, 2022, 16:45 IST

About Cell

The term ‘cell’ was coined by Robert Hooke in 1665 in his book Micrographia after examining thin slices of cork under a self designed primitive microscope. He had actually seen the dead walls of plant cells, which had lost their living contents and looked like small rooms.Anton von Leeuwenhoek described free cells for the first time in 1674. Robert Brown in 1831 discovered nucleus, the most important component of every cell. By this time, it had also been known that the cells were surrounded by some sort of limiting membrane.

About basics of Cell Theory

Schleiden (1838) and Schwann (1839) gave the ‘cell theory’. Accordingly, all plants and animals are composed of cells and cell is the basic unit of life. In 1855, Rudolf Virchow presented the idea that all living cells arise from the pre-existing cells. This led to the modification of cell theory.

The cell theory is as follows

(a) All organisms are composed of cell and cell products.

(b) All metabolic reactions take place in cells. Thus, cells are structural and functional unit of life.

(d) Every organism start its life as a single cell.

Haeckel (1866) reported that nucleus stores and transmits heredity information.

Discovery of electron microscope in 1940 made it possible to study complex structure of the cell and its organelles.

All living organisms are composed of one or more cells and accordingly, they are termed unicellular organisms (e.g., Amoeba) and multi-cellular organisms (e.g., plants and animals). In the former, a single cell constitutes a whole organism while in the latter, number of cells group together and acquire different functions to form various body parts.

All multi-cellular organisms show division of labour, i.e., different parts perform different functions. In fact, every living cell has got a division of labour. Its different cell organelles perform special functions and, therefore, constitute the basic building block ‘the cell’. Thus, cell is the structural and functional unit of living organisms.

Components of Cell

All cells have three major functional regions :

Plasma membrane (cell membrane) and cell wall

The Nucleus

The Cytoplasm

Each cell has three common features – plasma membrane, nuclear material (may or may not be bound by a membrane) and cytoplasm. All activities inside the cell and interactions of the cell with its environment are possible due to above three features.

Among living forms, viruses are the non-cellular or a-cellular organisms. They possess genetic material (DNA or RNA) enclosed in a protein coat. They do not show characteristics of life until they enter a living body to use its cell machinery to reproduce.Prokaryotes and Eukaryotes

Based on complexity of organization, cellular organisms are grouped as prokaryotes and eukaryotes.

Prokaryotes are the most primitive organisms (e.g., bacteria, blue-green algae or cyanobacteria) which lack nuclear membrane around their genetic material which is called nucleoid. They also do not contain membrane-bound cell organelles in the cytoplasm. Ribosomes are, however, present.

Eukaryotes have elaborate internal organization. Every eukaryotic cell contains a plasma membrane, membrane-bound nucleus containing the genetic material and other membrane-bound cell organelles in the cytoplasm. The organelles compartmentalize the cell to facilitate specific metabolic functions. Examples of eukaryotes are protists, fungi, plants and animals