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After a lot of researches, the revolutionary idea that all living organisms were made of cells was proposed; this gave life to modern biology: a completely new way of observing and studying the cells.
Electronic microscope
1. Transmission microscopes: the flow of electrons crosses the slide and meets the receiving screen, situated at the end of the microscope which projects an image in black and white. In this way we can visualize the inside of the cell.
2. Scanning microscopes: with these microscopes we have a three-dimensional vision of the outside of the cell with an almost atomic resolution. The slide, in fact, is covered with a metal (gold is usually used) to divert the electrons.
In the first decade of the XX century many scientists focused their studies on the behaviour of the chromosomes during the cellular division: at that moment it was understood that chromosomes transmitted the hereditary information. However, after 1920, scientists specified that it was the genes, contained inside the chromosomes, that transmitted the hereditary information from generation to generation: the study of the functions of the cell had begun, apart from examination of its structure. In order to study this, scientists were helped by the invention of the electronic microscope that exploits a group of electrons inserted inside the same microscope, because it is more penetrating, and therefore more effective than the optic microscope. This electronic microscope allows examination of cells that are not recognized with optic microscope. The main electronic microscopes are:
The use of the electronic microscopes has provided powerful resolutions that showed submicroscopics organisms like endo-plasmatic reticulum, lysosomes, Golgi system, vacuoles, centrioles, microfibres, microfilaments, microtubules and plastidi. The electronic microscope allowed scientists to explore the enormous complexity of the cell.
Subsequently, in 1953, the discovery of the DNA structure by the biochemist American James D. Watson and the English biophysicist Francis Crick marked the beginning of molecular biology; still today it is one of the largest and most advanced areas of all sciences. Cellular death or apoptosis is one of the most important areas that molecular biology studies.
A million times a second, in a human body, cells self-destruct because this is one of the phases of a normal cycle of cellular substitution. Moreover, this seems to prevent lots of illnesses: in fact, if auto-destruction of the cell did not happen, it could still be divided and create cells already mutated that would gradually spread forming a growth called tumour. It can be benign, malignant or harmless and it could threaten the healthy tissues. Understanding how and when the cells become malignant (this is the objective of study of apoptosis) is one of the roads undertaken by scientists. Nowadays, they study the cell in depth by using very advanced microscopic investigation techniques , possible thanks to a co-focal microscope which supplies a superior optic resolution and the visualization of images are given in 3D guaranteeing the best sensitivity.
Therefore, as we have by now understood, the discovery of the cell is in continuous evolution. Today we have a clear idea about the cell, but who knows how many things can still be discovered using technological means which become more and more sophisticated. So, we wish a good research to everyone!
Bibliography
- Università degli studi della Tuscia - www.unitus.it/scienze/giovani/Pucciarmati/LA%20CELLULA.htm
- Patrizia Picchi -www.torinoscienza.it/Personaggi/apri?obj_id=189 - Last update 23/12/2002
- http://it.wikipedia.org/wiki/Cellula - Last update 01/04/2006
- Andrea Genre, Laboratorio di microscopie avanzate www.bioveg.unito.it/italiano/lma/confocal.htm
- http://encarta.msn.com/encyclopedia_761568585_3/Cell_(biology).html#s52
- http://encarta.msn.com/encyclopedia_761562052/Microscope.html
- http://encarta.msn.com/encyclopedia_761566325/Leeuwenhoek_Antoni_van.html#p2
Iconography
- Patrizia Picchi - www.torinoscienza.it/img/orig/it/s00/00/0006/000006de.jpg
- Mario Pagliario - www.qualitas1998.net/immagini/cells_biosil.jpg
- Democrazia elettronica della provincia Forlì-Cesena www.delfo.forli-cesena.it/itgsaffi/esbiol.html
- Liceo Scientifico Salvemini prof. V.Caruso - www.liceosalvemini.it/Biologia/cellula/Cellula%20Eucariote.gif – Last update 12/03/2006
- http://it.wikipedia.org/wiki/Immagine:Elektronenmikroskop.jpg
- http://upload.wikimedia.org/wikipedia/it/e/ed/Microscopio1.jpg
