Cell theory V/s cell principle


In this article you will find the detailed description of cell theory and shortcoming of cell theory. You will also know cell principles.

Introduction and history

The concept that cell is the basic unit of life is known as cell theory or cell doctrine. The first attempt to present a theory regarding cellular organization of living beings was made by a French scientist H.I. Dutrochet in 1824. In this context, Dutrochet postulated two views:

  • Every organism is composed of cells.

  • Cell is the basic unit of all organisms.


The actual cell theory was proposed by M. J. Schleiden, a German botanist. Shleiden found that all plant tissues were made of one or other kind of cells. Therefore, Schleiden (1838) concluded that cells constitute the ultimate units of all plant tissues. In other words, cells are organisms and entire plants and animals are aggregations of these organisms arranged according to a definite law. In 1839, Theodor Schwann a German zoologist studied different types of animal tissues including the development of the embryo. Theodor Schwann concluded that all the organisms are composed of essentially like parts namely cells.
Combined view of Schleiden and Schwann led to the formulation of the cell theory. Cell theory proposed that all living beings whether plants or animals are composed of an assemblage of cells which arise from the pre-existing cells and that the activities of the organism are the outcome of the activities of its constituent cells. Schleiden and Schwann are credited with formulating the observations in the form of a theory. This theory was, however, not able to explain how new cells are formed. Rudolf Virchow (1855) modified the cell theory and stated that new cells develop from the division of pre-existing cells (Omnis cellula-e-cellula). It is known as the law of cell lingeage.

Fundamental features of cell theory

The fundamental features of cell theory are as follows:

  • All living organisms are composed of different types of cells and their products.

  • All cells arise from pre-existing cells.

  • All the activities of an organism are the outcome of the activities of its constituent cells.

  • All cells are basically identical in their chemistry and physiology.

  • Each cell is made of protoplasm having a nucleus and is bounded by a cell membrane with or without a cell wall.


Objections or shortcomings of the cell theory

The shortcomings of cell theory are:

  • Schwann, for instance, believed that the cell could be spontaneously generated. But the studies of the developing embryos show that during growth, cells duplicated themselves by division.

  • In many organisms, the body is not differentiated into cells though it may have numerous nuclei.

  • Schleiden and Schwann did not know the mechanism of cell formation. Schleiden thought that new cells were developed from the nucleus or cryptoblast. Schwann believed that cells were developed spontaneously like a crystal.


Modern cell theory or cell principle

The cell principle is the modified or modern form of the cell theory. The cell theory stands today as cell principle. The main features of cell principle are given below:

  • All organisms are composed of cells and their products.

  • New cells arise from pre-existing cells.

  • All cells are basically, alike in chemical composition and metabolic activities.

  • All the activities of an organism as a whole are the outcome of the activities and interactions of the constituting the body of that organism.

  • Each cell is made of a small mass of protoplasm having a nucleus bounded by a cell membrane with or without a cell wall.

  • Cells are the hereditary unit of life as it contains the hereditary substance in its nucleus.

  • Growth of an organism involves the growth and multiplication of its cells.

  • Genetic pieces of information are stored and expressed inside the cell.

  • Basically all the cells are totipotent. I.e., a single cell give rise to the whole organism.

  • Each cell maintains its individuality. A cell has a specific internal environment and homeostasis.


Last words The modern cell theory or cell principle is better than cell theory because of the following reasons:

  • Cell principle is applicable for almost to all living things, microorganisms, plants and animals.

  • Cell principle incorporates nearly all the modern findings of a cell .


Comments

Guest Author: Deepankar27 Jul 2019

I think the date of Schleiden is wrongly mentioned here. It should be 1838 but it is written as 1938.

Author: Saji Ganesh27 Jul 2019 Member Level: Diamond   Points : 0

Thank you Deepankar. The error has been rectified.



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