Cells constitute each and every part of living organisms. Although, their types may vary, there is no organism which does not have cell structure or cells and the mechanism of cell division and reproduction help each organism to evolve, develop, reproduce and eventually grow. Biologically, this is one of the most important processes which have been studied by many scientists since past many centuries. But even now there are some loopholes in the modern cell theory which still remain unanswered. And understandingly so, because this is the process of growth of life on earth and it certainly is very complex and intriguing!
All life is built on cells and is the basis of our existence on this planet. Robert Hooke in 1665 while examining some cork samples found out that the corks were made up of tiny porous structure resembling the honey comb. This he called You do not have access to view this node. Once the existence of cell was discovered scientists started decoding its function. Around 1839, Theodor Schwann and Matthias Jakob Schleiden put forth the thought that entire living species are composed of cells and that they are the basic block builders of life. In 1853, Rudolf Virchow on the basis of this earlier theory stated that all living cells are created from the pre-existing You do not have access to view this node. This is the most accepted cell theory as of today.
The modern cell theory says that apart from being structural units of body, cells are also integral units of heredity, reproduction and other functions. There are several organisms that are only made up of one cell. Almost all the cells have similar chemical compositions and the genetic material embedded within the cell differentiates the two organisms and not the You do not have access to view this node. So the cell theory concept of today is based on some general principles connected with construction in all living things. The six principles of cell theory are:
According to modern cell theory, there are two types of cells: Prokaryotes and Eukaryotes. Prokaryotes are the most primitive cells and do not have nucleus. Examples of these cell types are archae and bacteria. Eukaryotes have nucleus and comprise of genetic material in chromosomes. These types of cells encapsulate chloroplasts, endoplasmic reticulum, mitochondria, and lysosomes which are type of organelles.
Cell theory has brought a new evolution. Some studies like Stem cell research or decoding human genome is based on cell theory. The deeper understanding related to cells and their activities have helped mankind take bigger leaps in forward direction in various branches of hereditary ailments like heart disease or specific types of cancer.
The debate is still on whether viruses are living organisms are not. Viruses have been found to contain genetic information in their DNA or RNA but there is no presence of materials which behave like You do not have access to view this node. Hence despite of carrying various life properties (e.g. You do not have access to view this node), they cannot be considered as cells as they do not possess cellular material.